This section provides a description of each keyword and its usage.
acl <aclname> <criterion> [flags] [operator] <value> ...
Declare or complete an access list.
May be used in sections :
defaults |
frontend |
listen |
backend |
Example:
acl invalid_src src 0.0.0.0/7 224.0.0.0/3
acl invalid_src src_port 0:1023
acl local_dst hdr(host) -i localhost
See section 7 about ACL usage.
backlog <conns>
Give hints to the system about the approximate listen backlog desired size
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<conns> is the number of pending connections. Depending on the operating
system, it may represent the number of already acknowledged
connections, of non-acknowledged ones, or both.
In order to protect against SYN flood attacks, one solution is to increase
the system's SYN backlog size. Depending on the system, sometimes it is just
tunable via a system parameter, sometimes it is not adjustable at all, and
sometimes the system relies on hints given by the application at the time of
the listen() syscall. By default, HAProxy passes the frontend's maxconn value
to the listen() syscall. On systems which can make use of this value, it can
sometimes be useful to be able to specify a different value, hence this
backlog parameter.
On Linux 2.4, the parameter is ignored by the system. On Linux 2.6, it is
used as a hint and the system accepts up to the smallest greater power of
two, and never more than some limits (usually 32768).
See also : "
maxconn" and the target operating system's tuning guide.
balance <algorithm> [ <arguments> ]
balance url_param <param> [check_post]
Define the load balancing algorithm to be used in a backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<algorithm> is the algorithm used to select a server when doing load
balancing. This only applies when no persistence information
is available, or when a connection is redispatched to another
server. <algorithm> may be one of the following :
roundrobin Each server is used in turns, according to their weights.
This is the smoothest and fairest algorithm when the server's
processing time remains equally distributed. This algorithm
is dynamic, which means that server weights may be adjusted
on the fly for slow starts for instance. It is limited by
design to 4095 active servers per backend. Note that in some
large farms, when a server becomes up after having been down
for a very short time, it may sometimes take a few hundreds
requests for it to be re-integrated into the farm and start
receiving traffic. This is normal, though very rare. It is
indicated here in case you would have the chance to observe
it, so that you don't worry.
static-rr Each server is used in turns, according to their weights.
This algorithm is as similar to roundrobin except that it is
static, which means that changing a server's weight on the
fly will have no effect. On the other hand, it has no design
limitation on the number of servers, and when a server goes
up, it is always immediately reintroduced into the farm, once
the full map is recomputed. It also uses slightly less CPU to
run (around -1%).
leastconn The server with the lowest number of connections receives the
connection. Round-robin is performed within groups of servers
of the same load to ensure that all servers will be used. Use
of this algorithm is recommended where very long sessions are
expected, such as LDAP, SQL, TSE, etc... but is not very well
suited for protocols using short sessions such as HTTP. This
algorithm is dynamic, which means that server weights may be
adjusted on the fly for slow starts for instance. It will
also consider the number of queued connections in addition to
the established ones in order to minimize queuing.
first The first server with available connection slots receives the
connection. The servers are chosen from the lowest numeric
identifier to the highest (see server parameter "id"), which
defaults to the server's position in the farm. Once a server
reaches its maxconn value, the next server is used. It does
not make sense to use this algorithm without setting maxconn.
The purpose of this algorithm is to always use the smallest
number of servers so that extra servers can be powered off
during non-intensive hours. This algorithm ignores the server
weight, and brings more benefit to long session such as RDP
or IMAP than HTTP, though it can be useful there too. In
order to use this algorithm efficiently, it is recommended
that a cloud controller regularly checks server usage to turn
them off when unused, and regularly checks backend queue to
turn new servers on when the queue inflates. Alternatively,
using "http-check send-state" may inform servers on the load.
source The source IP address is hashed and divided by the total
weight of the running servers to designate which server will
receive the request. This ensures that the same client IP
address will always reach the same server as long as no
server goes down or up. If the hash result changes due to the
number of running servers changing, many clients will be
directed to a different server. This algorithm is generally
used in TCP mode where no cookie may be inserted. It may also
be used on the Internet to provide a best-effort stickiness
to clients which refuse session cookies. This algorithm is
static by default, which means that changing a server's
weight on the fly will have no effect, but this can be
changed using "hash-type".
uri This algorithm hashes either the left part of the URI (before
the question mark) or the whole URI (if the "whole" parameter
is present) and divides the hash value by the total weight of
the running servers. The result designates which server will
receive the request. This ensures that the same URI will
always be directed to the same server as long as no server
goes up or down. This is used with proxy caches and
anti-virus proxies in order to maximize the cache hit rate.
Note that this algorithm may only be used in an HTTP backend.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
This algorithm supports two optional parameters "len" and
"depth", both followed by a positive integer number. These
options may be helpful when it is needed to balance servers
based on the beginning of the URI only. The "len" parameter
indicates that the algorithm should only consider that many
characters at the beginning of the URI to compute the hash.
Note that having "len" set to 1 rarely makes sense since most
URIs start with a leading "/".
The "depth" parameter indicates the maximum directory depth
to be used to compute the hash. One level is counted for each
slash in the request. If both parameters are specified, the
evaluation stops when either is reached.
A "path-only" parameter indicates that the hashing key starts
at the first '/' of the path. This can be used to ignore the
authority part of absolute URIs, and to make sure that HTTP/1
and HTTP/2 URIs will provide the same hash.
url_param The URL parameter specified in argument will be looked up in
the query string of each HTTP GET request.
If the modifier "check_post" is used, then an HTTP POST
request entity will be searched for the parameter argument,
when it is not found in a query string after a question mark
('?') in the URL. The message body will only start to be
analyzed once either the advertised amount of data has been
received or the request buffer is full. In the unlikely event
that chunked encoding is used, only the first chunk is
scanned. Parameter values separated by a chunk boundary, may
be randomly balanced if at all. This keyword used to support
an optional <max_wait> parameter which is now ignored.
If the parameter is found followed by an equal sign ('=') and
a value, then the value is hashed and divided by the total
weight of the running servers. The result designates which
server will receive the request.
This is used to track user identifiers in requests and ensure
that a same user ID will always be sent to the same server as
long as no server goes up or down. If no value is found or if
the parameter is not found, then a round robin algorithm is
applied. Note that this algorithm may only be used in an HTTP
backend. This algorithm is static by default, which means
that changing a server's weight on the fly will have no
effect, but this can be changed using "hash-type".
hdr(<name>) The HTTP header <name> will be looked up in each HTTP
request. Just as with the equivalent ACL 'hdr()' function,
the header name in parenthesis is not case sensitive. If the
header is absent or if it does not contain any value, the
roundrobin algorithm is applied instead.
An optional 'use_domain_only' parameter is available, for
reducing the hash algorithm to the main domain part with some
specific headers such as 'Host'. For instance, in the Host
value "haproxy.1wt.eu", only "1wt" will be considered.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
random
random(<draws>)
A random number will be used as the key for the consistent
hashing function. This means that the servers' weights are
respected, dynamic weight changes immediately take effect, as
well as new server additions. Random load balancing can be
useful with large farms or when servers are frequently added
or removed as it may avoid the hammering effect that could
result from roundrobin or leastconn in this situation. The
hash-balance-factor directive can be used to further improve
fairness of the load balancing, especially in situations
where servers show highly variable response times. When an
argument <draws> is present, it must be an integer value one
or greater, indicating the number of draws before selecting
the least loaded of these servers. It was indeed demonstrated
that picking the least loaded of two servers is enough to
significantly improve the fairness of the algorithm, by
always avoiding to pick the most loaded server within a farm
and getting rid of any bias that could be induced by the
unfair distribution of the consistent list. Higher values N
will take away N-1 of the highest loaded servers at the
expense of performance. With very high values, the algorithm
will converge towards the leastconn's result but much slower.
The default value is 2, which generally shows very good
distribution and performance. This algorithm is also known as
the Power of Two Random Choices and is described here :
http://www.eecs.harvard.edu/~michaelm/postscripts/handbook2001.pdf
rdp-cookie
rdp-cookie(<name>)
The RDP cookie <name> (or "mstshash" if omitted) will be
looked up and hashed for each incoming TCP request. Just as
with the equivalent ACL 'req_rdp_cookie()' function, the name
is not case-sensitive. This mechanism is useful as a degraded
persistence mode, as it makes it possible to always send the
same user (or the same session ID) to the same server. If the
cookie is not found, the normal roundrobin algorithm is
used instead.
Note that for this to work, the frontend must ensure that an
RDP cookie is already present in the request buffer. For this
you must use 'tcp-request content accept' rule combined with
a 'req_rdp_cookie_cnt' ACL.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
See also the rdp_cookie pattern fetch function.
<arguments> is an optional list of arguments which may be needed by some
algorithms. Right now, only "url_param" and "uri" support an
optional argument.
The load balancing algorithm of a backend is set to roundrobin when no other
algorithm, mode nor option have been set. The algorithm may only be set once
for each backend.
With authentication schemes that require the same connection like NTLM, URI
based algorithms must not be used, as they would cause subsequent requests
to be routed to different backend servers, breaking the invalid assumptions
NTLM relies on.
Examples :
balance roundrobin
balance url_param userid
balance url_param session_id check_post 64
balance hdr(User-Agent)
balance hdr(host)
balance hdr(Host) use_domain_only
Note: the following caveats and limitations on using the "check_post"
extension with "url_param" must be considered :
- all POST requests are eligible for consideration, because there is no way
to determine if the parameters will be found in the body or entity which
may contain binary data. Therefore another method may be required to
restrict consideration of POST requests that have no URL parameters in
the body. (see acl http_end)
- using a <max_wait> value larger than the request buffer size does not
make sense and is useless. The buffer size is set at build time, and
defaults to 16 kB.
- Content-Encoding is not supported, the parameter search will probably
fail; and load balancing will fall back to Round Robin.
- Expect: 100-continue is not supported, load balancing will fall back to
Round Robin.
- Transfer-Encoding (RFC7230 3.3.1) is only supported in the first chunk.
If the entire parameter value is not present in the first chunk, the
selection of server is undefined (actually, defined by how little
actually appeared in the first chunk).
- This feature does not support generation of a 100, 411 or 501 response.
- In some cases, requesting "check_post" MAY attempt to scan the entire
contents of a message body. Scanning normally terminates when linear
white space or control characters are found, indicating the end of what
might be a URL parameter list. This is probably not a concern with SGML
type message bodies.
See also : "
dispatch", "
cookie", "
transparent", "
hash-type" and "
http_proxy".
bind [<address>]:<port_range> [, ...] [param*]
bind /<path> [, ...] [param*]
Define one or several listening addresses and/or ports in a frontend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<address> is optional and can be a host name, an IPv4 address, an IPv6
address, or '*'. It designates the address the frontend will
listen on. If unset, all IPv4 addresses of the system will be
listened on. The same will apply for '*' or the system's
special address "0.0.0.0". The IPv6 equivalent is '::'.
Optionally, an address family prefix may be used before the
address to force the family regardless of the address format,
which can be useful to specify a path to a unix socket with
no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'udp@' -> address is resolved as IPv4 or IPv6 and
protocol UDP is used. Currently those listeners are
supported only in log-forward sections.
- 'udp4@' -> address is always IPv4 and protocol UDP
is used. Currently those listeners are supported
only in log-forward sections.
- 'udp6@' -> address is always IPv6 and protocol UDP
is used. Currently those listeners are supported
only in log-forward sections.
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only).
Note: since abstract sockets are not "rebindable", they
do not cope well with multi-process mode during
soft-restart, so it is better to avoid them if
nbproc is greater than 1. The effect is that if the
new process fails to start, only one of the old ones
will be able to rebind to the socket.
- 'fd@<n>' -> use file descriptor <n> inherited from the
parent. The fd must be bound and may or may not already
be listening.
- 'sockpair@<n>'-> like fd@ but you must use the fd of a
connected unix socket or of a socketpair. The bind waits
to receive a FD over the unix socket and uses it as if it
was the FD of an accept(). Should be used carefully.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment
variables.
<port_range> is either a unique TCP port, or a port range for which the
proxy will accept connections for the IP address specified
above. The port is mandatory for TCP listeners. Note that in
the case of an IPv6 address, the port is always the number
after the last colon (':'). A range can either be :
- a numerical port (ex: '80')
- a dash-delimited ports range explicitly stating the lower
and upper bounds (ex: '2000-2100') which are included in
the range.
Particular care must be taken against port ranges, because
every <address:port> couple consumes one socket (= a file
descriptor), so it's easy to consume lots of descriptors
with a simple range, and to run out of sockets. Also, each
<address:port> couple must be used only once among all
instances running on a same system. Please note that binding
to ports lower than 1024 generally require particular
privileges to start the program, which are independent of
the 'uid' parameter.
<path> is a UNIX socket path beginning with a slash ('/'). This is
alternative to the TCP listening port. HAProxy will then
receive UNIX connections on the socket located at this place.
The path must begin with a slash and by default is absolute.
It can be relative to the prefix defined by "unix-bind" in
the global section. Note that the total length of the prefix
followed by the socket path cannot exceed some system limits
for UNIX sockets, which commonly are set to 107 characters.
<param*> is a list of parameters common to all sockets declared on the
same line. These numerous parameters depend on OS and build
options and have a complete section dedicated to them. Please
refer to section 5 to for more details.
It is possible to specify a list of address:port combinations delimited by
commas. The frontend will then listen on all of these addresses. There is no
fixed limit to the number of addresses and ports which can be listened on in
a frontend, as well as there is no limit to the number of "bind" statements
in a frontend.
Example :
listen http_proxy
bind :80,:443
bind 10.0.0.1:10080,10.0.0.1:10443
bind /var/run/ssl-frontend.sock user root mode 600 accept-proxy
listen http_https_proxy
bind :80
bind :443 ssl crt /etc/haproxy/site.pem
listen http_https_proxy_explicit
bind ipv6@:80
bind ipv4@public_ssl:443 ssl crt /etc/haproxy/site.pem
bind [email protected] user root mode 600 accept-proxy
listen external_bind_app1
bind "fd@${FD_APP1}"
Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
sun_path length is used for the address length. Some other programs
such as socat use the string length only by default. Pass the option
",unix-tightsocklen=0" to any abstract socket definition in socat to
make it compatible with HAProxy's.
See also : "
source", "
option forwardfor", "
unix-bind" and the PROXY protocol documentation, and
section 5 about bind options.
bind-process [ all | odd | even | <process_num>[-[<process_num>]] ] ...
Limit visibility of an instance to a certain set of processes numbers.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :all All process will see this instance. This is the default. It
may be used to override a default value.
odd This instance will be enabled on processes 1,3,5,...63. This
option may be combined with other numbers.
even This instance will be enabled on processes 2,4,6,...64. This
option may be combined with other numbers. Do not use it
with less than 2 processes otherwise some instances might be
missing from all processes.
process_num The instance will be enabled on this process number or range,
whose values must all be between 1 and 32 or 64 depending on
the machine's word size. Ranges can be partially defined. The
higher bound can be omitted. In such case, it is replaced by
the corresponding maximum value. If a proxy is bound to
process numbers greater than the configured global.nbproc, it
will either be forced to process #1 if a single process was
specified, or to all processes otherwise.
This keyword limits binding of certain instances to certain processes. This
is useful in order not to have too many processes listening to the same
ports. For instance, on a dual-core machine, it might make sense to set
'nbproc 2' in the global section, then distributes the listeners among 'odd'
and 'even' instances.
At the moment, it is not possible to reference more than 32 or 64 processes
using this keyword, but this should be more than enough for most setups.
Please note that 'all' really means all processes regardless of the machine's
word size, and is not limited to the first 32 or 64.
Each "bind" line may further be limited to a subset of the proxy's processes,
please consult the "process" bind keyword in section 5.1.
When a frontend has no explicit "bind-process" line, it tries to bind to all
the processes referenced by its "bind" lines. That means that frontends can
easily adapt to their listeners' processes.
If some backends are referenced by frontends bound to other processes, the
backend automatically inherits the frontend's processes.
Example :
listen app_ip1
bind 10.0.0.1:80
bind-process odd
listen app_ip2
bind 10.0.0.2:80
bind-process even
listen management
bind 10.0.0.3:80
bind-process 1 2 3 4
listen management
bind 10.0.0.4:80
bind-process 1-4
See also : "
nbproc" in global section, and "
process" in
section 5.1.
capture cookie <name> len <length>
Capture and log a cookie in the request and in the response.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the beginning of the name of the cookie to capture. In order
to match the exact name, simply suffix the name with an equal
sign ('='). The full name will appear in the logs, which is
useful with application servers which adjust both the cookie name
and value (e.g. ASPSESSIONXXX).
<length> is the maximum number of characters to report in the logs, which
include the cookie name, the equal sign and the value, all in the
standard "name=value" form. The string will be truncated on the
right if it exceeds <length>.
Only the first cookie is captured. Both the "cookie" request headers and the
"set-cookie" response headers are monitored. This is particularly useful to
check for application bugs causing session crossing or stealing between
users, because generally the user's cookies can only change on a login page.
When the cookie was not presented by the client, the associated log column
will report "-". When a request does not cause a cookie to be assigned by the
server, a "-" is reported in the response column.
The capture is performed in the frontend only because it is necessary that
the log format does not change for a given frontend depending on the
backends. This may change in the future. Note that there can be only one
"capture cookie" statement in a frontend. The maximum capture length is set
by the global "tune.http.cookielen" setting and defaults to 63 characters. It
is not possible to specify a capture in a "defaults" section.
Example:
capture cookie ASPSESSION len 32
See also : "
capture request header", "
capture response header" as well as
section 8 about logging.
Capture and log the last occurrence of the specified request header.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the name of the header to capture. The header names are not
case-sensitive, but it is a common practice to write them as they
appear in the requests, with the first letter of each word in
upper case. The header name will not appear in the logs, only the
value is reported, but the position in the logs is respected.
<length> is the maximum number of characters to extract from the value and
report in the logs. The string will be truncated on the right if
it exceeds <length>.
The complete value of the last occurrence of the header is captured. The
value will be added to the logs between braces ('{}'). If multiple headers
are captured, they will be delimited by a vertical bar ('|') and will appear
in the same order they were declared in the configuration. Non-existent
headers will be logged just as an empty string. Common uses for request
header captures include the "Host" field in virtual hosting environments, the
"Content-length" when uploads are supported, "User-agent" to quickly
differentiate between real users and robots, and "X-Forwarded-For" in proxied
environments to find where the request came from.
Note that when capturing headers such as "User-agent", some spaces may be
logged, making the log analysis more difficult. Thus be careful about what
you log if you know your log parser is not smart enough to rely on the
braces.
There is no limit to the number of captured request headers nor to their
length, though it is wise to keep them low to limit memory usage per session.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture request header Host len 15
capture request header X-Forwarded-For len 15
capture request header Referer len 15
See also : "
capture cookie", "
capture response header" as well as
section 8 about logging.
Capture and log the last occurrence of the specified response header.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the name of the header to capture. The header names are not
case-sensitive, but it is a common practice to write them as they
appear in the response, with the first letter of each word in
upper case. The header name will not appear in the logs, only the
value is reported, but the position in the logs is respected.
<length> is the maximum number of characters to extract from the value and
report in the logs. The string will be truncated on the right if
it exceeds <length>.
The complete value of the last occurrence of the header is captured. The
result will be added to the logs between braces ('{}') after the captured
request headers. If multiple headers are captured, they will be delimited by
a vertical bar ('|') and will appear in the same order they were declared in
the configuration. Non-existent headers will be logged just as an empty
string. Common uses for response header captures include the "Content-length"
header which indicates how many bytes are expected to be returned, the
"Location" header to track redirections.
There is no limit to the number of captured response headers nor to their
length, though it is wise to keep them low to limit memory usage per session.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture response header Content-length len 9
capture response header Location len 15
See also : "
capture cookie", "
capture request header" as well as
section 8 about logging.
clitcpka-cnt <count>
Sets the maximum number of keepalive probes TCP should send before dropping
the connection on the client side.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<count> is the maximum number of keepalive probes.
This keyword corresponds to the socket option TCP_KEEPCNT. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_probes) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
See also : "
option clitcpka", "
clitcpka-idle", "
clitcpka-intvl".
clitcpka-idle <timeout>
Sets the time the connection needs to remain idle before TCP starts sending
keepalive probes, if enabled the sending of TCP keepalive packets on the
client side.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<timeout> is the time the connection needs to remain idle before TCP starts
sending keepalive probes. It is specified in seconds by default,
but can be in any other unit if the number is suffixed by the
unit, as explained at the top of this document.
This keyword corresponds to the socket option TCP_KEEPIDLE. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_time) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
See also : "
option clitcpka", "
clitcpka-cnt", "
clitcpka-intvl".
clitcpka-intvl <timeout>
Sets the time between individual keepalive probes on the client side.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<timeout> is the time between individual keepalive probes. It is specified
in seconds by default, but can be in any other unit if the number
is suffixed by the unit, as explained at the top of this
document.
This keyword corresponds to the socket option TCP_KEEPINTVL. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_intvl) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
See also : "
option clitcpka", "
clitcpka-cnt", "
clitcpka-idle".
compression algo <algorithm> ...
compression type <mime type> ...
compression offload
Enable HTTP compression.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :algo is followed by the list of supported compression algorithms.
type is followed by the list of MIME types that will be compressed.
offload makes HAProxy work as a compression offloader only (see notes).
The currently supported algorithms are :
identity this is mostly for debugging, and it was useful for developing
the compression feature. Identity does not apply any change on
data.
gzip applies gzip compression. This setting is only available when
support for zlib or libslz was built in.
deflate same as "gzip", but with deflate algorithm and zlib format.
Note that this algorithm has ambiguous support on many
browsers and no support at all from recent ones. It is
strongly recommended not to use it for anything else than
experimentation. This setting is only available when support
for zlib or libslz was built in.
raw-deflate same as "deflate" without the zlib wrapper, and used as an
alternative when the browser wants "deflate". All major
browsers understand it and despite violating the standards,
it is known to work better than "deflate", at least on MSIE
and some versions of Safari. Do not use it in conjunction
with "deflate", use either one or the other since both react
to the same Accept-Encoding token. This setting is only
available when support for zlib or libslz was built in.
Compression will be activated depending on the Accept-Encoding request
header. With identity, it does not take care of that header.
If backend servers support HTTP compression, these directives
will be no-op: HAProxy will see the compressed response and will not
compress again. If backend servers do not support HTTP compression and
there is Accept-Encoding header in request, HAProxy will compress the
matching response.
The "offload" setting makes HAProxy remove the Accept-Encoding header to
prevent backend servers from compressing responses. It is strongly
recommended not to do this because this means that all the compression work
will be done on the single point where HAProxy is located. However in some
deployment scenarios, HAProxy may be installed in front of a buggy gateway
with broken HTTP compression implementation which can't be turned off.
In that case HAProxy can be used to prevent that gateway from emitting
invalid payloads. In this case, simply removing the header in the
configuration does not work because it applies before the header is parsed,
so that prevents HAProxy from compressing. The "offload" setting should
then be used for such scenarios. Note: for now, the "offload" setting is
ignored when set in a defaults section.
Compression is disabled when:
* the request does not advertise a supported compression algorithm in the
"Accept-Encoding" header
* the response message is not HTTP/1.1 or above
* HTTP status code is not one of 200, 201, 202, or 203
* response contain neither a "Content-Length" header nor a
"Transfer-Encoding" whose last value is "chunked"
* response contains a "Content-Type" header whose first value starts with
"multipart"
* the response contains the "no-transform" value in the "Cache-control"
header
* User-Agent matches "Mozilla/4" unless it is MSIE 6 with XP SP2, or MSIE 7
and later
* The response contains a "Content-Encoding" header, indicating that the
response is already compressed (see compression offload)
* The response contains an invalid "ETag" header or multiple ETag headers
Note: The compression does not emit the Warning header.
Examples :
compression algo gzip
compression type text/html text/plain
cookie <name> [ rewrite | insert | prefix ] [ indirect ] [ nocache ] [ postonly ] [ preserve ] [ httponly ] [ secure ] [ domain <domain> ]* [ maxidle <idle> ] [ maxlife <life> ] [ dynamic ] [ attr <value> ]*
Enable cookie-based persistence in a backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the name of the cookie which will be monitored, modified or
inserted in order to bring persistence. This cookie is sent to
the client via a "Set-Cookie" header in the response, and is
brought back by the client in a "Cookie" header in all requests.
Special care should be taken to choose a name which does not
conflict with any likely application cookie. Also, if the same
backends are subject to be used by the same clients (e.g.
HTTP/HTTPS), care should be taken to use different cookie names
between all backends if persistence between them is not desired.
rewrite This keyword indicates that the cookie will be provided by the
server and that HAProxy will have to modify its value to set the
server's identifier in it. This mode is handy when the management
of complex combinations of "Set-cookie" and "Cache-control"
headers is left to the application. The application can then
decide whether or not it is appropriate to emit a persistence
cookie. Since all responses should be monitored, this mode
doesn't work in HTTP tunnel mode. Unless the application
behavior is very complex and/or broken, it is advised not to
start with this mode for new deployments. This keyword is
incompatible with "insert" and "prefix".
insert This keyword indicates that the persistence cookie will have to
be inserted by HAProxy in server responses if the client did not
already have a cookie that would have permitted it to access this
server. When used without the "preserve" option, if the server
emits a cookie with the same name, it will be removed before
processing. For this reason, this mode can be used to upgrade
existing configurations running in the "rewrite" mode. The cookie
will only be a session cookie and will not be stored on the
client's disk. By default, unless the "indirect" option is added,
the server will see the cookies emitted by the client. Due to
caching effects, it is generally wise to add the "nocache" or
"postonly" keywords (see below). The "insert" keyword is not
compatible with "rewrite" and "prefix".
prefix This keyword indicates that instead of relying on a dedicated
cookie for the persistence, an existing one will be completed.
This may be needed in some specific environments where the client
does not support more than one single cookie and the application
already needs it. In this case, whenever the server sets a cookie
named <name>, it will be prefixed with the server's identifier
and a delimiter. The prefix will be removed from all client
requests so that the server still finds the cookie it emitted.
Since all requests and responses are subject to being modified,
this mode doesn't work with tunnel mode. The "prefix" keyword is
not compatible with "rewrite" and "insert". Note: it is highly
recommended not to use "indirect" with "prefix", otherwise server
cookie updates would not be sent to clients.
indirect When this option is specified, no cookie will be emitted to a
client which already has a valid one for the server which has
processed the request. If the server sets such a cookie itself,
it will be removed, unless the "preserve" option is also set. In
"insert" mode, this will additionally remove cookies from the
requests transmitted to the server, making the persistence
mechanism totally transparent from an application point of view.
Note: it is highly recommended not to use "indirect" with
"prefix", otherwise server cookie updates would not be sent to
clients.
nocache This option is recommended in conjunction with the insert mode
when there is a cache between the client and HAProxy, as it
ensures that a cacheable response will be tagged non-cacheable if
a cookie needs to be inserted. This is important because if all
persistence cookies are added on a cacheable home page for
instance, then all customers will then fetch the page from an
outer cache and will all share the same persistence cookie,
leading to one server receiving much more traffic than others.
See also the "insert" and "postonly" options.
postonly This option ensures that cookie insertion will only be performed
on responses to POST requests. It is an alternative to the
"nocache" option, because POST responses are not cacheable, so
this ensures that the persistence cookie will never get cached.
Since most sites do not need any sort of persistence before the
first POST which generally is a login request, this is a very
efficient method to optimize caching without risking to find a
persistence cookie in the cache.
See also the "insert" and "nocache" options.
preserve This option may only be used with "insert" and/or "indirect". It
allows the server to emit the persistence cookie itself. In this
case, if a cookie is found in the response, HAProxy will leave it
untouched. This is useful in order to end persistence after a
logout request for instance. For this, the server just has to
emit a cookie with an invalid value (e.g. empty) or with a date in
the past. By combining this mechanism with the "disable-on-404"
check option, it is possible to perform a completely graceful
shutdown because users will definitely leave the server after
they logout.
httponly This option tells HAProxy to add an "HttpOnly" cookie attribute
when a cookie is inserted. This attribute is used so that a
user agent doesn't share the cookie with non-HTTP components.
Please check RFC6265 for more information on this attribute.
secure This option tells HAProxy to add a "Secure" cookie attribute when
a cookie is inserted. This attribute is used so that a user agent
never emits this cookie over non-secure channels, which means
that a cookie learned with this flag will be presented only over
SSL/TLS connections. Please check RFC6265 for more information on
this attribute.
domain This option allows to specify the domain at which a cookie is
inserted. It requires exactly one parameter: a valid domain
name. If the domain begins with a dot, the browser is allowed to
use it for any host ending with that name. It is also possible to
specify several domain names by invoking this option multiple
times. Some browsers might have small limits on the number of
domains, so be careful when doing that. For the record, sending
10 domains to MSIE 6 or Firefox 2 works as expected.
maxidle This option allows inserted cookies to be ignored after some idle
time. It only works with insert-mode cookies. When a cookie is
sent to the client, the date this cookie was emitted is sent too.
Upon further presentations of this cookie, if the date is older
than the delay indicated by the parameter (in seconds), it will
be ignored. Otherwise, it will be refreshed if needed when the
response is sent to the client. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (e.g. after a farm size change). When
this option is set and a cookie has no date, it is always
accepted, but gets refreshed in the response. This maintains the
ability for admins to access their sites. Cookies that have a
date in the future further than 24 hours are ignored. Doing so
lets admins fix timezone issues without risking kicking users off
the site.
maxlife This option allows inserted cookies to be ignored after some life
time, whether they're in use or not. It only works with insert
mode cookies. When a cookie is first sent to the client, the date
this cookie was emitted is sent too. Upon further presentations
of this cookie, if the date is older than the delay indicated by
the parameter (in seconds), it will be ignored. If the cookie in
the request has no date, it is accepted and a date will be set.
Cookies that have a date in the future further than 24 hours are
ignored. Doing so lets admins fix timezone issues without risking
kicking users off the site. Contrary to maxidle, this value is
not refreshed, only the first visit date counts. Both maxidle and
maxlife may be used at the time. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (e.g. after a farm size change). This
is stronger than the maxidle method in that it forces a
redispatch after some absolute delay.
dynamic Activate dynamic cookies. When used, a session cookie is
dynamically created for each server, based on the IP and port
of the server, and a secret key, specified in the
"dynamic-cookie-key" backend directive.
The cookie will be regenerated each time the IP address change,
and is only generated for IPv4/IPv6.
attr This option tells HAProxy to add an extra attribute when a
cookie is inserted. The attribute value can contain any
characters except control ones or ";". This option may be
repeated.
There can be only one persistence cookie per HTTP backend, and it can be
declared in a defaults section. The value of the cookie will be the value
indicated after the "cookie" keyword in a "server" statement. If no cookie
is declared for a given server, the cookie is not set.
Examples :
cookie JSESSIONID prefix
cookie SRV insert indirect nocache
cookie SRV insert postonly indirect
cookie SRV insert indirect nocache maxidle 30m maxlife 8h
See also : "balance source", "
capture cookie", "
server" and "
ignore-persist".
declare capture [ request | response ] len <length>
Declares a capture slot.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments:<length> is the length allowed for the capture.
This declaration is only available in the frontend or listen section, but the
reserved slot can be used in the backends. The "request" keyword allocates a
capture slot for use in the request, and "response" allocates a capture slot
for use in the response.
See also: "
capture-req", "
capture-res" (sample converters), "
capture.req.hdr", "
capture.res.hdr" (sample fetches), "
http-request capture" and "
http-response capture".
default-server [param*]
Change default options for a server in a backend
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments:<param*> is a list of parameters for this server. The "default-server"
keyword accepts an important number of options and has a complete
section dedicated to it. Please refer to section 5 for more
details.
Example :
default-server inter 1000 weight 13
See also: "
server" and
section 5 about server options
default_backend <backend>
Specify the backend to use when no "use_backend" rule has been matched.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<backend> is the name of the backend to use.
When doing content-switching between frontend and backends using the
"use_backend" keyword, it is often useful to indicate which backend will be
used when no rule has matched. It generally is the dynamic backend which
will catch all undetermined requests.
Example :
use_backend dynamic if url_dyn
use_backend static if url_css url_img extension_img
default_backend dynamic
See also : "
use_backend"
description <string>
Describe a listen, frontend or backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : string
Allows to add a sentence to describe the related object in the HAProxy HTML
stats page. The description will be printed on the right of the object name
it describes.
No need to backslash spaces in the <string> arguments.
disabled
Disable a proxy, frontend or backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
The "disabled" keyword is used to disable an instance, mainly in order to
liberate a listening port or to temporarily disable a service. The instance
will still be created and its configuration will be checked, but it will be
created in the "stopped" state and will appear as such in the statistics. It
will not receive any traffic nor will it send any health-checks or logs. It
is possible to disable many instances at once by adding the "disabled"
keyword in a "defaults" section.
See also : "
enabled"
dispatch <address>:<port>
Set a default server address
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<address> is the IPv4 address of the default server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up.
<ports> is a mandatory port specification. All connections will be sent
to this port, and it is not permitted to use port offsets as is
possible with normal servers.
The "dispatch" keyword designates a default server for use when no other
server can take the connection. In the past it was used to forward non
persistent connections to an auxiliary load balancer. Due to its simple
syntax, it has also been used for simple TCP relays. It is recommended not to
use it for more clarity, and to use the "server" directive instead.
See also : "
server"
dynamic-cookie-key <string>
Set the dynamic cookie secret key for a backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : The secret key to be used.
When dynamic cookies are enabled (see the "dynamic" directive for cookie),
a dynamic cookie is created for each server (unless one is explicitly
specified on the "server" line), using a hash of the IP address of the
server, the TCP port, and the secret key.
That way, we can ensure session persistence across multiple load-balancers,
even if servers are dynamically added or removed.
enabled
Enable a proxy, frontend or backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
The "enabled" keyword is used to explicitly enable an instance, when the
defaults has been set to "disabled". This is very rarely used.
See also : "
disabled"
errorfile <code> <file>
Return a file contents instead of errors generated by HAProxy
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
413, 425, 429, 500, 501, 502, 503, and 504.
<file> designates a file containing the full HTTP response. It is
recommended to follow the common practice of appending ".http" to
the filename so that people do not confuse the response with HTML
error pages, and to use absolute paths, since files are read
before any chroot is performed.
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "monitor-uri" rule.
The files are parsed when HAProxy starts and must be valid according to the
HTTP specification. They should not exceed the configured buffer size
(BUFSIZE), which generally is 16 kB, otherwise an internal error will be
returned. It is also wise not to put any reference to local contents
(e.g. images) in order to avoid loops between the client and HAProxy when all
servers are down, causing an error to be returned instead of an
image. Finally, The response cannot exceed (tune.bufsize - tune.maxrewrite)
so that "http-after-response" rules still have room to operate (see
"tune.maxrewrite").
The files are read at the same time as the configuration and kept in memory.
For this reason, the errors continue to be returned even when the process is
chrooted, and no file change is considered while the process is running. A
simple method for developing those files consists in associating them to the
403 status code and interrogating a blocked URL.
See also : "
http-error", "
errorloc", "
errorloc302", "
errorloc303"
Example :
errorfile 400 /etc/haproxy/errorfiles/400badreq.http
errorfile 408 /dev/null
errorfile 403 /etc/haproxy/errorfiles/403forbid.http
errorfile 503 /etc/haproxy/errorfiles/503sorry.http
errorfiles <name> [<code> ...]
Import, fully or partially, the error files defined in the <name> http-errors
section.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the name of an existing http-errors section.
<code> is a HTTP status code. Several status code may be listed.
Currently, HAProxy is capable of generating codes 200, 400, 401,
403, 404, 405, 407, 408, 410, 413, 425, 429, 500, 501, 502, 503,
and 504.
Errors defined in the http-errors section with the name <name> are imported
in the current proxy. If no status code is specified, all error files of the
http-errors section are imported. Otherwise, only error files associated to
the listed status code are imported. Those error files override the already
defined custom errors for the proxy. And they may be overridden by following
ones. Functionally, it is exactly the same as declaring all error files by
hand using "errorfile" directives.
See also : "
http-error", "
errorfile", "
errorloc", "
errorloc302" , "
errorloc303" and
section 3.8 about http-errors.
Example :
errorfiles generic
errorfiles site-1 403 404
errorloc <code> <url>
errorloc302 <code> <url>
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
413, 425, 429, 500, 501, 502, 503, and 504.
<url> it is the exact contents of the "Location" header. It may contain
either a relative URI to an error page hosted on the same site,
or an absolute URI designating an error page on another site.
Special care should be given to relative URIs to avoid redirect
loops if the URI itself may generate the same error (e.g. 500).
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "monitor-uri" rule.
Note that both keyword return the HTTP 302 status code, which tells the
client to fetch the designated URL using the same HTTP method. This can be
quite problematic in case of non-GET methods such as POST, because the URL
sent to the client might not be allowed for something other than GET. To
work around this problem, please use "errorloc303" which send the HTTP 303
status code, indicating to the client that the URL must be fetched with a GET
request.
See also : "
http-error", "
errorfile", "
errorloc303"
errorloc303 <code> <url>
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
413, 425, 429, 500, 501, 502, 503, and 504.
<url> it is the exact contents of the "Location" header. It may contain
either a relative URI to an error page hosted on the same site,
or an absolute URI designating an error page on another site.
Special care should be given to relative URIs to avoid redirect
loops if the URI itself may generate the same error (e.g. 500).
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "monitor-uri" rule.
Note that both keyword return the HTTP 303 status code, which tells the
client to fetch the designated URL using the same HTTP GET method. This
solves the usual problems associated with "errorloc" and the 302 code. It is
possible that some very old browsers designed before HTTP/1.1 do not support
it, but no such problem has been reported till now.
See also : "
http-error", "
errorfile", "
errorloc", "
errorloc302"
email-alert from <emailaddr>
Declare the from email address to be used in both the envelope and header
of email alerts. This is the address that email alerts are sent from.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<emailaddr> is the from email address to use when sending email alerts
Also requires "email-alert mailers" and "email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
See also : "
email-alert level", "
email-alert mailers", "
email-alert myhostname", "
email-alert to",
section 3.6 about mailers.
email-alert level <level>
Declare the maximum log level of messages for which email alerts will be
sent. This acts as a filter on the sending of email alerts.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<level> One of the 8 syslog levels:
emerg alert crit err warning notice info debug
The above syslog levels are ordered from lowest to highest.
By default level is alert
Also requires "email-alert from", "email-alert mailers" and
"email-alert to" to be set and if so sending email alerts is enabled
for the proxy.
Alerts are sent when :
* An un-paused server is marked as down and <level> is alert or lower
* A paused server is marked as down and <level> is notice or lower
* A server is marked as up or enters the drain state and <level>
is notice or lower
* "option log-health-checks" is enabled, <level> is info or lower,
and a health check status update occurs
See also : "
email-alert from", "
email-alert mailers", "
email-alert myhostname", "
email-alert to",
section 3.6 about mailers.
email-alert mailers <mailersect>
Declare the mailers to be used when sending email alerts
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<mailersect> is the name of the mailers section to send email alerts.
Also requires "email-alert from" and "email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
See also : "
email-alert from", "
email-alert level", "
email-alert myhostname", "
email-alert to",
section 3.6 about mailers.
email-alert myhostname <hostname>
Declare the to hostname address to be used when communicating with
mailers.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<hostname> is the hostname to use when communicating with mailers
By default the systems hostname is used.
Also requires "email-alert from", "email-alert mailers" and
"email-alert to" to be set and if so sending email alerts is enabled
for the proxy.
See also : "
email-alert from", "
email-alert level", "
email-alert mailers", "
email-alert to",
section 3.6 about mailers.
email-alert to <emailaddr>
Declare both the recipient address in the envelope and to address in the
header of email alerts. This is the address that email alerts are sent to.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<emailaddr> is the to email address to use when sending email alerts
Also requires "email-alert mailers" and "email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
See also : "
email-alert from", "
email-alert level", "
email-alert mailers", "
email-alert myhostname",
section 3.6 about mailers.
force-persist { if | unless } <condition>
Declare a condition to force persistence on down servers
May be used in sections :
defaults |
frontend |
listen |
backend |
By default, requests are not dispatched to down servers. It is possible to
force this using "option persist", but it is unconditional and redispatches
to a valid server if "option redispatch" is set. That leaves with very little
possibilities to force some requests to reach a server which is artificially
marked down for maintenance operations.
The "force-persist" statement allows one to declare various ACL-based
conditions which, when met, will cause a request to ignore the down status of
a server and still try to connect to it. That makes it possible to start a
server, still replying an error to the health checks, and run a specially
configured browser to test the service. Among the handy methods, one could
use a specific source IP address, or a specific cookie. The cookie also has
the advantage that it can easily be added/removed on the browser from a test
page. Once the service is validated, it is then possible to open the service
to the world by returning a valid response to health checks.
The forced persistence is enabled when an "if" condition is met, or unless an
"unless" condition is met. The final redispatch is always disabled when this
is used.
See also : "
option redispatch", "
ignore-persist", "
persist", and
section 7 about ACL usage.
filter <name> [param*]
Add the filter <name> in the filter list attached to the proxy.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the name of the filter. Officially supported filters are
referenced in section 9.
<param*> is a list of parameters accepted by the filter <name>. The
parsing of these parameters are the responsibility of the
filter. Please refer to the documentation of the corresponding
filter (section 9) for all details on the supported parameters.
Multiple occurrences of the filter line can be used for the same proxy. The
same filter can be referenced many times if needed.
Example:
listen
bind *:80
filter trace name BEFORE-HTTP-COMP
filter compression
filter trace name AFTER-HTTP-COMP
compression algo gzip
compression offload
server srv1 192.168.0.1:80
See also : section 9.
fullconn <conns>
Specify at what backend load the servers will reach their maxconn
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<conns> is the number of connections on the backend which will make the
servers use the maximal number of connections.
When a server has a "maxconn" parameter specified, it means that its number
of concurrent connections will never go higher. Additionally, if it has a
"minconn" parameter, it indicates a dynamic limit following the backend's
load. The server will then always accept at least <minconn> connections,
never more than <maxconn>, and the limit will be on the ramp between both
values when the backend has less than <conns> concurrent connections. This
makes it possible to limit the load on the servers during normal loads, but
push it further for important loads without overloading the servers during
exceptional loads.
Since it's hard to get this value right, HAProxy automatically sets it to
10% of the sum of the maxconns of all frontends that may branch to this
backend (based on "use_backend" and "default_backend" rules). That way it's
safe to leave it unset. However, "use_backend" involving dynamic names are
not counted since there is no way to know if they could match or not.
Example :
backend dynamic
fullconn 10000
server srv1 dyn1:80 minconn 100 maxconn 1000
server srv2 dyn2:80 minconn 100 maxconn 1000
See also : "
maxconn", "
server"
grace <time> (deprecated)
Maintain a proxy operational for some time after a soft stop
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<time> is the time (by default in milliseconds) for which the instance
will remain operational with the frontend sockets still listening
when a soft-stop is received via the SIGUSR1 signal.
This may be used to ensure that the services disappear in a certain order.
This was designed so that frontends which are dedicated to monitoring by an
external equipment fail immediately while other ones remain up for the time
needed by the equipment to detect the failure.
Note that currently, there is very little benefit in using this parameter,
and it may in fact complicate the soft-reconfiguration process more than
simplify it.
hash-balance-factor <factor>
Specify the balancing factor for bounded-load consistent hashing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<factor> is the control for the maximum number of concurrent requests to
send to a server, expressed as a percentage of the average number
of concurrent requests across all of the active servers.
Specifying a "hash-balance-factor" for a server with "hash-type consistent"
enables an algorithm that prevents any one server from getting too many
requests at once, even if some hash buckets receive many more requests than
others. Setting <factor> to 0 (the default) disables the feature. Otherwise,
<factor> is a percentage greater than 100. For example, if <factor> is 150,
then no server will be allowed to have a load more than 1.5 times the average.
If server weights are used, they will be respected.
If the first-choice server is disqualified, the algorithm will choose another
server based on the request hash, until a server with additional capacity is
found. A higher <factor> allows more imbalance between the servers, while a
lower <factor> means that more servers will be checked on average, affecting
performance. Reasonable values are from 125 to 200.
This setting is also used by "balance random" which internally relies on the
consistent hashing mechanism.
See also : "
balance" and "
hash-type".
hash-type <method> <function> <modifier>
Specify a method to use for mapping hashes to servers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<method> is the method used to select a server from the hash computed by
the <function> :
map-based the hash table is a static array containing all alive servers.
The hashes will be very smooth, will consider weights, but
will be static in that weight changes while a server is up
will be ignored. This means that there will be no slow start.
Also, since a server is selected by its position in the array,
most mappings are changed when the server count changes. This
means that when a server goes up or down, or when a server is
added to a farm, most connections will be redistributed to
different servers. This can be inconvenient with caches for
instance.
consistent the hash table is a tree filled with many occurrences of each
server. The hash key is looked up in the tree and the closest
server is chosen. This hash is dynamic, it supports changing
weights while the servers are up, so it is compatible with the
slow start feature. It has the advantage that when a server
goes up or down, only its associations are moved. When a
server is added to the farm, only a few part of the mappings
are redistributed, making it an ideal method for caches.
However, due to its principle, the distribution will never be
very smooth and it may sometimes be necessary to adjust a
server's weight or its ID to get a more balanced distribution.
In order to get the same distribution on multiple load
balancers, it is important that all servers have the exact
same IDs. Note: consistent hash uses sdbm and avalanche if no
hash function is specified.
<function> is the hash function to be used :
sdbm this function was created initially for sdbm (a public-domain
reimplementation of ndbm) database library. It was found to do
well in scrambling bits, causing better distribution of the keys
and fewer splits. It also happens to be a good general hashing
function with good distribution, unless the total server weight
is a multiple of 64, in which case applying the avalanche
modifier may help.
djb2 this function was first proposed by Dan Bernstein many years ago
on comp.lang.c. Studies have shown that for certain workload this
function provides a better distribution than sdbm. It generally
works well with text-based inputs though it can perform extremely
poorly with numeric-only input or when the total server weight is
a multiple of 33, unless the avalanche modifier is also used.
wt6 this function was designed for HAProxy while testing other
functions in the past. It is not as smooth as the other ones, but
is much less sensible to the input data set or to the number of
servers. It can make sense as an alternative to sdbm+avalanche or
djb2+avalanche for consistent hashing or when hashing on numeric
data such as a source IP address or a visitor identifier in a URL
parameter.
crc32 this is the most common CRC32 implementation as used in Ethernet,
gzip, PNG, etc. It is slower than the other ones but may provide
a better distribution or less predictable results especially when
used on strings.
<modifier> indicates an optional method applied after hashing the key :
avalanche This directive indicates that the result from the hash
function above should not be used in its raw form but that
a 4-byte full avalanche hash must be applied first. The
purpose of this step is to mix the resulting bits from the
previous hash in order to avoid any undesired effect when
the input contains some limited values or when the number of
servers is a multiple of one of the hash's components (64
for SDBM, 33 for DJB2). Enabling avalanche tends to make the
result less predictable, but it's also not as smooth as when
using the original function. Some testing might be needed
with some workloads. This hash is one of the many proposed
by Bob Jenkins.
The default hash type is "map-based" and is recommended for most usages. The
default function is "sdbm", the selection of a function should be based on
the range of the values being hashed.
See also : "
balance", "
hash-balance-factor", "
server"
http-after-response <action> <options...> [ { if | unless } <condition> ]
Access control for all Layer 7 responses (server, applet/service and internal
ones).
May be used in sections :
defaults |
frontend |
listen |
backend |
The http-after-response statement defines a set of rules which apply to layer
7 processing. The rules are evaluated in their declaration order when they
are met in a frontend, listen or backend section. Any rule may optionally be
followed by an ACL-based condition, in which case it will only be evaluated
if the condition is true. Since these rules apply on responses, the backend
rules are applied first, followed by the frontend's rules.
Unlike http-response rules, these ones are applied on all responses, the
server ones but also to all responses generated by HAProxy. These rules are
evaluated at the end of the responses analysis, before the data forwarding.
The first keyword is the rule's action. The supported actions are described
below.
There is no limit to the number of http-after-response statements per
instance.
Note: Errors emitted in early stage of the request parsing are handled by the
multiplexer at a lower level, before any http analysis. Thus no
http-after-response ruleset is evaluated on these errors.
Example:
http-after-response set-header Strict-Transport-Security "max-age=31536000"
http-after-response set-header Cache-Control "no-store,no-cache,private"
http-after-response set-header Pragma "no-cache"
This appends an HTTP header field whose name is specified in <name> and whose
value is defined by <fmt> which follows the log-format rules (see Custom Log
Format in section 8.2.4). This may be used to send a cookie to a client for
example, or to pass some internal information.
This rule is not final, so it is possible to add other similar rules.
Note that header addition is performed immediately, so one rule might reuse
the resulting header from a previous rule.
http-after-response allow [ { if | unless } <condition> ]
This stops the evaluation of the rules and lets the response pass the check.
No further "http-after-response" rules are evaluated.
This removes all HTTP header fields whose name is specified in <name>. <meth>
is the matching method, applied on the header name. Supported matching methods
are "str" (exact match), "beg" (prefix match), "end" (suffix match), "sub"
(substring match) and "reg" (regex match). If not specified, exact matching
method is used.
This works like "http-response replace-header".
Example:
http-after-response replace-header Set-Cookie (C=[^;]*);(.*) \1;ip=%bi;\2
Set-Cookie: C=1; expires=Tue, 14-Jun-2016 01:40:45 GMT
Set-Cookie: C=1;ip=192.168.1.20; expires=Tue, 14-Jun-2016 01:40:45 GMT
http-after-response replace-value <name> <regex-match> <replace-fmt> [ { if | unless } <condition> ]
This works like "http-response replace-value".
Example:
http-after-response replace-value Cache-control ^public$ private
Cache-Control: max-age=3600, public
Cache-Control: max-age=3600, private
This does the same as "add-header" except that the header name is first
removed if it existed. This is useful when passing security information to
the server, where the header must not be manipulated by external users.
http-after-response set-status <status> [reason <str>] [ { if | unless } <condition> ]
This replaces the response status code with <status> which must be an integer
between 100 and 999. Optionally, a custom reason text can be provided defined
by <str>, or the default reason for the specified code will be used as a
fallback.
Example:
http-response set-status 431
http-response set-status 503 reason "Slow Down"
http-after-response set-var(<var-name>) <expr> [ { if | unless } <condition> ]
This is used to set the contents of a variable. The variable is declared
inline.
Arguments:<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed are:
"proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction
(request and response)
"req" : the variable is shared only during request
processing
"res" : the variable is shared only during response
processing
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.'
and '_'.
<expr> Is a standard HAProxy expression formed by a sample-fetch
followed by some converters.
Example:
http-after-response set-var(sess.last_redir) res.hdr(location)
http-after-response strict-mode { on | off }
This enables or disables the strict rewriting mode for following rules. It
does not affect rules declared before it and it is only applicable on rules
performing a rewrite on the responses. When the strict mode is enabled, any
rewrite failure triggers an internal error. Otherwise, such errors are
silently ignored. The purpose of the strict rewriting mode is to make some
rewrites optional while others must be performed to continue the response
processing.
By default, the strict rewriting mode is enabled. Its value is also reset
when a ruleset evaluation ends. So, for instance, if you change the mode on
the backend, the default mode is restored when HAProxy starts the frontend
rules evaluation.
http-after-response unset-var(<var-name>) [ { if | unless } <condition> ]
This is used to unset a variable. See "http-after-response set-var" for
details about <var-name>.
Example:
http-after-response unset-var(sess.last_redir)
Defines a comment for the following the http-check rule, reported in logs if
it fails.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<string> is the comment message to add in logs if the following http-check
rule fails.
It only works for connect, send and expect rules. It is useful to make
user-friendly error reporting.
See also : "
option httpchk", "
http-check connect", "
http-check send" and "
http-check expect".
http-check connect [default] [port <expr>] [addr <ip>] [send-proxy] [via-socks4] [ssl] [sni <sni>] [alpn <alpn>] [linger] [proto <name>] [comment <msg>]
Opens a new connection to perform an HTTP health check
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
default Use default options of the server line to do the health
checks. The server options are used only if not redefined.
port <expr> if not set, check port or server port is used.
It tells HAProxy where to open the connection to.
<port> must be a valid TCP port source integer, from 1 to
65535 or an sample-fetch expression.
addr <ip> defines the IP address to do the health check.
send-proxy send a PROXY protocol string
via-socks4 enables outgoing health checks using upstream socks4 proxy.
ssl opens a ciphered connection
sni <sni> specifies the SNI to use to do health checks over SSL.
alpn <alpn> defines which protocols to advertise with ALPN. The protocol
list consists in a comma-delimited list of protocol names,
for instance: "h2,http/1.1". If it is not set, the server ALPN
is used.
proto <name> forces the multiplexer's protocol to use for this connection.
It must be an HTTP mux protocol and it must be usable on the
backend side. The list of available protocols is reported in
haproxy -vv.
linger cleanly close the connection instead of using a single RST.
Just like tcp-check health checks, it is possible to configure the connection
to use to perform HTTP health check. This directive should also be used to
describe a scenario involving several request/response exchanges, possibly on
different ports or with different servers.
When there are no TCP port configured on the server line neither server port
directive, then the first step of the http-check sequence must be to specify
the port with a "http-check connect".
In an http-check ruleset a 'connect' is required, it is also mandatory to start
the ruleset with a 'connect' rule. Purpose is to ensure admin know what they
do.
When a connect must start the ruleset, if may still be preceded by set-var,
unset-var or comment rules.
Examples :
option httpchk
http-check connect
http-check send meth GET uri / ver HTTP/1.1 hdr host haproxy.1wt.eu
http-check expect status 200-399
http-check connect port 443 ssl sni haproxy.1wt.eu
http-check send meth GET uri / ver HTTP/1.1 hdr host haproxy.1wt.eu
http-check expect status 200-399
server www 10.0.0.1 check port 80
See also : "
option httpchk", "
http-check send", "
http-check expect"
http-check disable-on-404
Enable a maintenance mode upon HTTP/404 response to health-checks
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When this option is set, a server which returns an HTTP code 404 will be
excluded from further load-balancing, but will still receive persistent
connections. This provides a very convenient method for Web administrators
to perform a graceful shutdown of their servers. It is also important to note
that a server which is detected as failed while it was in this mode will not
generate an alert, just a notice. If the server responds 2xx or 3xx again, it
will immediately be reinserted into the farm. The status on the stats page
reports "NOLB" for a server in this mode. It is important to note that this
option only works in conjunction with the "httpchk" option. If this option
is used with "http-check expect", then it has precedence over it so that 404
responses will still be considered as soft-stop. Note also that a stopped
server will stay stopped even if it replies 404s. This option is only
evaluated for running servers.
See also : "
option httpchk" and "
http-check expect".
http-check expect [min-recv <int>] [comment <msg>] [ok-status <st>] [error-status <st>] [tout-status <st>] [on-success <fmt>] [on-error <fmt>] [status-code <expr>] [!] <match> <pattern>
Make HTTP health checks consider response contents or specific status codes
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
min-recv is optional and can define the minimum amount of data required to
evaluate the current expect rule. If the number of received bytes
is under this limit, the check will wait for more data. This
option can be used to resolve some ambiguous matching rules or to
avoid executing costly regex matches on content known to be still
incomplete. If an exact string is used, the minimum between the
string length and this parameter is used. This parameter is
ignored if it is set to -1. If the expect rule does not match,
the check will wait for more data. If set to 0, the evaluation
result is always conclusive.
ok-status <st> is optional and can be used to set the check status if
the expect rule is successfully evaluated and if it is
the last rule in the tcp-check ruleset. "L7OK", "L7OKC",
"L6OK" and "L4OK" are supported :
- L7OK : check passed on layer 7
- L7OKC : check conditionally passed on layer 7, set
server to NOLB state.
- L6OK : check passed on layer 6
- L4OK : check passed on layer 4
By default "L7OK" is used.
error-status <st> is optional and can be used to set the check status if
an error occurred during the expect rule evaluation.
"L7OKC", "L7RSP", "L7STS", "L6RSP" and "L4CON" are
supported :
- L7OKC : check conditionally passed on layer 7, set
server to NOLB state.
- L7RSP : layer 7 invalid response - protocol error
- L7STS : layer 7 response error, for example HTTP 5xx
- L6RSP : layer 6 invalid response - protocol error
- L4CON : layer 1-4 connection problem
By default "L7RSP" is used.
tout-status <st> is optional and can be used to set the check status if
a timeout occurred during the expect rule evaluation.
"L7TOUT", "L6TOUT", and "L4TOUT" are supported :
- L7TOUT : layer 7 (HTTP/SMTP) timeout
- L6TOUT : layer 6 (SSL) timeout
- L4TOUT : layer 1-4 timeout
By default "L7TOUT" is used.
on-success <fmt> is optional and can be used to customize the
informational message reported in logs if the expect
rule is successfully evaluated and if it is the last rule
in the tcp-check ruleset. <fmt> is a log-format string.
on-error <fmt> is optional and can be used to customize the
informational message reported in logs if an error
occurred during the expect rule evaluation. <fmt> is a
log-format string.
<match> is a keyword indicating how to look for a specific pattern in the
response. The keyword may be one of "status", "rstatus", "hdr",
"fhdr", "string", or "rstring". The keyword may be preceded by an
exclamation mark ("!") to negate the match. Spaces are allowed
between the exclamation mark and the keyword. See below for more
details on the supported keywords.
<pattern> is the pattern to look for. It may be a string, a regular
expression or a more complex pattern with several arguments. If
the string pattern contains spaces, they must be escaped with the
usual backslash ('\').
By default, "option httpchk" considers that response statuses 2xx and 3xx
are valid, and that others are invalid. When "http-check expect" is used,
it defines what is considered valid or invalid. Only one "http-check"
statement is supported in a backend. If a server fails to respond or times
out, the check obviously fails. The available matches are :
status <codes> : test the status codes found parsing <codes> string. it
must be a comma-separated list of status codes or range
codes. A health check response will be considered as
valid if the response's status code matches any status
code or is inside any range of the list. If the "status"
keyword is prefixed with "!", then the response will be
considered invalid if the status code matches.
rstatus <regex> : test a regular expression for the HTTP status code.
A health check response will be considered valid if the
response's status code matches the expression. If the
"rstatus" keyword is prefixed with "!", then the response
will be considered invalid if the status code matches.
This is mostly used to check for multiple codes.
hdr { name | name-lf } [ -m <meth> ] <name>
[ { value | value-lf } [ -m <meth> ] <value> :
test the specified header pattern on the HTTP response
headers. The name pattern is mandatory but the value
pattern is optional. If not specified, only the header
presence is verified. <meth> is the matching method,
applied on the header name or the header value. Supported
matching methods are "str" (exact match), "beg" (prefix
match), "end" (suffix match), "sub" (substring match) or
"reg" (regex match). If not specified, exact matching
method is used. If the "name-lf" parameter is used,
<name> is evaluated as a log-format string. If "value-lf"
parameter is used, <value> is evaluated as a log-format
string. These parameters cannot be used with the regex
matching method. Finally, the header value is considered
as comma-separated list. Note that matchings are case
insensitive on the header names.
fhdr { name | name-lf } [ -m <meth> ] <name>
[ { value | value-lf } [ -m <meth> ] <value> :
test the specified full header pattern on the HTTP
response headers. It does exactly the same than "hdr"
keyword, except the full header value is tested, commas
are not considered as delimiters.
string <string> : test the exact string match in the HTTP response body.
A health check response will be considered valid if the
response's body contains this exact string. If the
"string" keyword is prefixed with "!", then the response
will be considered invalid if the body contains this
string. This can be used to look for a mandatory word at
the end of a dynamic page, or to detect a failure when a
specific error appears on the check page (e.g. a stack
trace).
rstring <regex> : test a regular expression on the HTTP response body.
A health check response will be considered valid if the
response's body matches this expression. If the "rstring"
keyword is prefixed with "!", then the response will be
considered invalid if the body matches the expression.
This can be used to look for a mandatory word at the end
of a dynamic page, or to detect a failure when a specific
error appears on the check page (e.g. a stack trace).
string-lf <fmt> : test a log-format string match in the HTTP response body.
A health check response will be considered valid if the
response's body contains the string resulting of the
evaluation of <fmt>, which follows the log-format rules.
If prefixed with "!", then the response will be
considered invalid if the body contains the string.
It is important to note that the responses will be limited to a certain size
defined by the global "tune.bufsize" option, which defaults to 16384 bytes.
Thus, too large responses may not contain the mandatory pattern when using
"string" or "rstring". If a large response is absolutely required, it is
possible to change the default max size by setting the global variable.
However, it is worth keeping in mind that parsing very large responses can
waste some CPU cycles, especially when regular expressions are used, and that
it is always better to focus the checks on smaller resources.
In an http-check ruleset, the last expect rule may be implicit. If no expect
rule is specified after the last "http-check send", an implicit expect rule
is defined to match on 2xx or 3xx status codes. It means this rule is also
defined if there is no "http-check" rule at all, when only "option httpchk"
is set.
Last, if "http-check expect" is combined with "http-check disable-on-404",
then this last one has precedence when the server responds with 404.
Examples :
http-check expect status 200,201,300-310
http-check expect header name "set-cookie" value -m beg "sessid="
http-check expect ! string SQL\ Error
http-check expect ! rstatus ^5
http-check expect rstring <!--tag:[0-9a-f]*--></html>
See also : "
option httpchk", "
http-check connect", "
http-check disable-on-404" and "
http-check send".
http-check send [meth <method>] [{ uri <uri> | uri-lf <fmt> }>] [ver <version>] [hdr <name> <fmt>]* [{ body <string> | body-lf <fmt> }] [comment <msg>]
Add a possible list of headers and/or a body to the request sent during HTTP
health checks.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
meth <method> is the optional HTTP method used with the requests. When not
set, the "OPTIONS" method is used, as it generally requires
low server processing and is easy to filter out from the
logs. Any method may be used, though it is not recommended
to invent non-standard ones.
uri <uri> is optional and set the URI referenced in the HTTP requests
to the string <uri>. It defaults to "/" which is accessible
by default on almost any server, but may be changed to any
other URI. Query strings are permitted.
uri-lf <fmt> is optional and set the URI referenced in the HTTP requests
using the log-format string <fmt>. It defaults to "/" which
is accessible by default on almost any server, but may be
changed to any other URI. Query strings are permitted.
ver <version> is the optional HTTP version string. It defaults to
"HTTP/1.0" but some servers might behave incorrectly in HTTP
1.0, so turning it to HTTP/1.1 may sometimes help. Note that
the Host field is mandatory in HTTP/1.1, use "hdr" argument
to add it.
hdr <name> <fmt> adds the HTTP header field whose name is specified in
<name> and whose value is defined by <fmt>, which follows
to the log-format rules.
body <string> add the body defined by <string> to the request sent during
HTTP health checks. If defined, the "Content-Length" header
is thus automatically added to the request.
body-lf <fmt> add the body defined by the log-format string <fmt> to the
request sent during HTTP health checks. If defined, the
"Content-Length" header is thus automatically added to the
request.
In addition to the request line defined by the "option httpchk" directive,
this one is the valid way to add some headers and optionally a body to the
request sent during HTTP health checks. If a body is defined, the associate
"Content-Length" header is automatically added. Thus, this header or
"Transfer-encoding" header should not be present in the request provided by
"http-check send". If so, it will be ignored. The old trick consisting to add
headers after the version string on the "option httpchk" line is now
deprecated.
Also "http-check send" doesn't support HTTP keep-alive. Keep in mind that it
will automatically append a "Connection: close" header, unless a Connection
header has already already been configured via a hdr entry.
Note that the Host header and the request authority, when both defined, are
automatically synchronized. It means when the HTTP request is sent, when a
Host is inserted in the request, the request authority is accordingly
updated. Thus, don't be surprised if the Host header value overwrites the
configured request authority.
Note also for now, no Host header is automatically added in HTTP/1.1 or above
requests. You should add it explicitly.
See also : "
option httpchk", "
http-check send-state" and "
http-check expect".
http-check send-state
Enable emission of a state header with HTTP health checks
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When this option is set, HAProxy will systematically send a special header
"X-Haproxy-Server-State" with a list of parameters indicating to each server
how they are seen by HAProxy. This can be used for instance when a server is
manipulated without access to HAProxy and the operator needs to know whether
HAProxy still sees it up or not, or if the server is the last one in a farm.
The header is composed of fields delimited by semi-colons, the first of which
is a word ("UP", "DOWN", "NOLB"), possibly followed by a number of valid
checks on the total number before transition, just as appears in the stats
interface. Next headers are in the form "<variable>=<value>", indicating in
no specific order some values available in the stats interface :
- a variable "address", containing the address of the backend server.
This corresponds to the <address> field in the server declaration. For
unix domain sockets, it will read "unix".
- a variable "port", containing the port of the backend server. This
corresponds to the <port> field in the server declaration. For unix
domain sockets, it will read "unix".
- a variable "name", containing the name of the backend followed by a slash
("/") then the name of the server. This can be used when a server is
checked in multiple backends.
- a variable "node" containing the name of the HAProxy node, as set in the
global "node" variable, otherwise the system's hostname if unspecified.
- a variable "weight" indicating the weight of the server, a slash ("/")
and the total weight of the farm (just counting usable servers). This
helps to know if other servers are available to handle the load when this
one fails.
- a variable "scur" indicating the current number of concurrent connections
on the server, followed by a slash ("/") then the total number of
connections on all servers of the same backend.
- a variable "qcur" indicating the current number of requests in the
server's queue.
Example of a header received by the application server :
>>> X-Haproxy-Server-State: UP 2/3; name=bck/srv2; node=lb1; weight=1/2; \
scur=13/22; qcur=0
See also : "
option httpchk", "
http-check disable-on-404" and "
http-check send".
http-check set-var(<var-name>) <expr>
This operation sets the content of a variable. The variable is declared inline.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed for http-check are:
"proc" : the variable is shared with the whole process.
"sess" : the variable is shared with the tcp-check session.
"check": the variable is declared for the lifetime of the tcp-check.
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.',
and '-'.
<expr> Is a sample-fetch expression potentially followed by converters.
Examples :
http-check set-var(check.port) int(1234)
http-check unset-var(<var-name>)
Free a reference to a variable within its scope.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed for http-check are:
"proc" : the variable is shared with the whole process.
"sess" : the variable is shared with the tcp-check session.
"check": the variable is declared for the lifetime of the tcp-check.
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.',
and '-'.
Examples :
http-check unset-var(check.port)
http-error status <code> [content-type <type>] [ { default-errorfiles | errorfile <file> | errorfiles <name> | file <file> | lf-file <file> | string <str> | lf-string <fmt> } ] [ hdr <name> <fmt> ]*
Defines a custom error message to use instead of errors generated by HAProxy.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :status <code> is the HTTP status code. It must be specified.
Currently, HAProxy is capable of generating codes
200, 400, 401, 403, 404, 405, 407, 408, 410, 413, 425,
429, 500, 501, 502, 503, and 504.
content-type <type> is the response content type, for instance
"text/plain". This parameter is ignored and should be
omitted when an errorfile is configured or when the
payload is empty. Otherwise, it must be defined.
default-errorfiles Reset the previously defined error message for current
proxy for the status <code>. If used on a backend, the
frontend error message is used, if defined. If used on
a frontend, the default error message is used.
errorfile <file> designates a file containing the full HTTP response.
It is recommended to follow the common practice of
appending ".http" to the filename so that people do
not confuse the response with HTML error pages, and to
use absolute paths, since files are read before any
chroot is performed.
errorfiles <name> designates the http-errors section to use to import
the error message with the status code <code>. If no
such message is found, the proxy's error messages are
considered.
file <file> specifies the file to use as response payload. If the
file is not empty, its content-type must be set as
argument to "content-type", otherwise, any
"content-type" argument is ignored. <file> is
considered as a raw string.
string <str> specifies the raw string to use as response payload.
The content-type must always be set as argument to
"content-type".
lf-file <file> specifies the file to use as response payload. If the
file is not empty, its content-type must be set as
argument to "content-type", otherwise, any
"content-type" argument is ignored. <file> is
evaluated as a log-format string.
lf-string <str> specifies the log-format string to use as response
payload. The content-type must always be set as
argument to "content-type".
hdr <name> <fmt> adds to the response the HTTP header field whose name
is specified in <name> and whose value is defined by
<fmt>, which follows to the log-format rules.
This parameter is ignored if an errorfile is used.
This directive may be used instead of "errorfile", to define a custom error
message. As "errorfile" directive, it is used for errors detected and
returned by HAProxy. If an errorfile is defined, it is parsed when HAProxy
starts and must be valid according to the HTTP standards. The generated
response must not exceed the configured buffer size (BUFFSIZE), otherwise an
internal error will be returned. Finally, if you consider to use some
http-after-response rules to rewrite these errors, the reserved buffer space
should be available (see "tune.maxrewrite").
The files are read at the same time as the configuration and kept in memory.
For this reason, the errors continue to be returned even when the process is
chrooted, and no file change is considered while the process is running.
Note: 400/408/500 errors emitted in early stage of the request parsing are
handled by the multiplexer at a lower level. No custom formatting is
supported at this level. Thus only static error messages, defined with
"errorfile" directive, are supported. However, this limitation only
exists during the request headers parsing or between two transactions.
See also : "
errorfile", "
errorfiles", "
errorloc", "
errorloc302", "
errorloc303" and
section 3.8 about http-errors.
http-request <action> [options...] [ { if | unless } <condition> ]
Access control for Layer 7 requests
May be used in sections :
defaults |
frontend |
listen |
backend |
The http-request statement defines a set of rules which apply to layer 7
processing. The rules are evaluated in their declaration order when they are
met in a frontend, listen or backend section. Any rule may optionally be
followed by an ACL-based condition, in which case it will only be evaluated
if the condition is true.
The first keyword is the rule's action. The supported actions are described
below.
There is no limit to the number of http-request statements per instance.
Example:
acl nagios src 192.168.129.3
acl local_net src 192.168.0.0/16
acl auth_ok http_auth(L1)
http-request allow if nagios
http-request allow if local_net auth_ok
http-request auth realm Gimme if local_net auth_ok
http-request deny
Example:
acl key req.hdr(X-Add-Acl-Key) -m found
acl add path /addacl
acl del path /delacl
acl myhost hdr(Host) -f myhost.lst
http-request add-acl(myhost.lst) %[req.hdr(X-Add-Acl-Key)] if key add
http-request del-acl(myhost.lst) %[req.hdr(X-Add-Acl-Key)] if key del
Example:
acl value req.hdr(X-Value) -m found
acl setmap path /setmap
acl delmap path /delmap
use_backend bk_appli if { hdr(Host),map_str(map.lst) -m found }
http-request set-map(map.lst) %[src] %[req.hdr(X-Value)] if setmap value
http-request del-map(map.lst) %[src] if delmap
See also : "
stats http-request",
section 3.4 about userlists and
section 7 about ACL usage.
http-request add-acl(<file-name>) <key fmt> [ { if | unless } <condition> ]
This is used to add a new entry into an ACL. The ACL must be loaded from a
file (even a dummy empty file). The file name of the ACL to be updated is
passed between parentheses. It takes one argument: <key fmt>, which follows
log-format rules, to collect content of the new entry. It performs a lookup
in the ACL before insertion, to avoid duplicated (or more) values. This
lookup is done by a linear search and can be expensive with large lists!
It is the equivalent of the "add acl" command from the stats socket, but can
be triggered by an HTTP request.
This appends an HTTP header field whose name is specified in <name> and
whose value is defined by <fmt> which follows the log-format rules (see
Custom Log Format in section 8.2.4). This is particularly useful to pass
connection-specific information to the server (e.g. the client's SSL
certificate), or to combine several headers into one. This rule is not
final, so it is possible to add other similar rules. Note that header
addition is performed immediately, so one rule might reuse the resulting
header from a previous rule.
http-request allow [ { if | unless } <condition> ]
This stops the evaluation of the rules and lets the request pass the check.
No further "http-request" rules are evaluated.
http-request auth [realm <realm>] [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately responds with an
HTTP 401 or 407 error code to invite the user to present a valid user name
and password. No further "http-request" rules are evaluated. An optional
"realm" parameter is supported, it sets the authentication realm that is
returned with the response (typically the application's name).
The corresponding proxy's error message is used. It may be customized using
an "errorfile" or an "http-error" directive. For 401 responses, all
occurrences of the WWW-Authenticate header are removed and replaced by a new
one with a basic authentication challenge for realm "<realm>". For 407
responses, the same is done on the Proxy-Authenticate header. If the error
message must not be altered, consider to use "http-request return" rule
instead.
Example:
acl auth_ok http_auth_group(L1) G1
http-request auth unless auth_ok
http-request cache-use <name> [ { if | unless } <condition> ]
See section 6.2 about cache setup.
http-request capture <sample> [ len <length> | id <id> ] [ { if | unless } <condition> ]
This captures sample expression <sample> from the request buffer, and
converts it to a string of at most <len> characters. The resulting string is
stored into the next request "capture" slot, so it will possibly appear next
to some captured HTTP headers. It will then automatically appear in the logs,
and it will be possible to extract it using sample fetch rules to feed it
into headers or anything. The length should be limited given that this size
will be allocated for each capture during the whole session life.
Please check section 7.3 (Fetching samples) and "capture request header" for
more information.
If the keyword "id" is used instead of "len", the action tries to store the
captured string in a previously declared capture slot. This is useful to run
captures in backends. The slot id can be declared by a previous directive
"http-request capture" or with the "declare capture" keyword.
When using this action in a backend, double check that the relevant
frontend(s) have the required capture slots otherwise, this rule will be
ignored at run time. This can't be detected at configuration parsing time
due to HAProxy's ability to dynamically resolve backend name at runtime.
http-request del-acl(<file-name>) <key fmt> [ { if | unless } <condition> ]
This is used to delete an entry from an ACL. The ACL must be loaded from a
file (even a dummy empty file). The file name of the ACL to be updated is
passed between parentheses. It takes one argument: <key fmt>, which follows
log-format rules, to collect content of the entry to delete.
It is the equivalent of the "del acl" command from the stats socket, but can
be triggered by an HTTP request.
This removes all HTTP header fields whose name is specified in <name>. <meth>
is the matching method, applied on the header name. Supported matching methods
are "str" (exact match), "beg" (prefix match), "end" (suffix match), "sub"
(substring match) and "reg" (regex match). If not specified, exact matching
method is used.
http-request del-map(<file-name>) <key fmt> [ { if | unless } <condition> ]
This is used to delete an entry from a MAP. The MAP must be loaded from a
file (even a dummy empty file). The file name of the MAP to be updated is
passed between parentheses. It takes one argument: <key fmt>, which follows
log-format rules, to collect content of the entry to delete.
It takes one argument: "file name" It is the equivalent of the "del map"
command from the stats socket, but can be triggered by an HTTP request.
http-request deny [deny_status <status>] [ { if | unless } <condition> ]
http-request deny [ { status | deny_status } <code>] [content-type <type>] [ { default-errorfiles | errorfile <file> | errorfiles <name> | file <file> | lf-file <file> | string <str> | lf-string <fmt> } ] [ hdr <name> <fmt> ]* [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately rejects the request.
By default an HTTP 403 error is returned. But the response may be customized
using same syntax than "http-request return" rules. Thus, see "http-request
return" for details. For compatibility purpose, when no argument is defined,
or only "deny_status", the argument "default-errorfiles" is implied. It means
"http-request deny [deny_status <status>]" is an alias of
"http-request deny [status <status>] default-errorfiles".
No further "http-request" rules are evaluated.
See also "http-request return".
http-request disable-l7-retry [ { if | unless } <condition> ]
This disables any attempt to retry the request if it fails for any other
reason than a connection failure. This can be useful for example to make
sure POST requests aren't retried on failure.
http-request do-resolve(<var>,<resolvers>,[ipv4,ipv6]) <expr> :
This action performs a DNS resolution of the output of <expr> and stores
the result in the variable <var>. It uses the DNS resolvers section
pointed by <resolvers>.
It is possible to choose a resolution preference using the optional
arguments 'ipv4' or 'ipv6'.
When performing the DNS resolution, the client side connection is on
pause waiting till the end of the resolution.
If an IP address can be found, it is stored into <var>. If any kind of
error occurs, then <var> is not set.
One can use this action to discover a server IP address at run time and
based on information found in the request (IE a Host header).
If this action is used to find the server's IP address (using the
"set-dst" action), then the server IP address in the backend must be set
to 0.0.0.0.
Example:
resolvers mydns
nameserver local 127.0.0.53:53
nameserver google 8.8.8.8:53
timeout retry 1s
hold valid 10s
hold nx 3s
hold other 3s
hold obsolete 0s
accepted_payload_size 8192
frontend fe
bind 10.42.0.1:80
http-request do-resolve(txn.myip,mydns,ipv4) hdr(Host),lower
http-request capture var(txn.myip) len 40
use_backend b_503 unless { var(txn.myip) -m found }
default_backend be
backend b_503
backend be
http-request deny if { var(txn.myip) -m ip 127.0.0.0/8 10.0.0.0/8 }
http-request set-dst var(txn.myip)
server clear 0.0.0.0:0
NOTE: Don't forget to set the "protection" rules to ensure HAProxy won't
be used to scan the network or worst won't loop over itself...
http-request early-hint <name> <fmt> [ { if | unless } <condition> ]
This is used to build an HTTP 103 Early Hints response prior to any other one.
This appends an HTTP header field to this response whose name is specified in
<name> and whose value is defined by <fmt> which follows the log-format rules
(see Custom Log Format in section 8.2.4). This is particularly useful to pass
to the client some Link headers to preload resources required to render the
HTML documents.
See RFC 8297 for more information.
http-request normalize-uri <normalizer> [ { if | unless } <condition> ]
http-request normalize-uri fragment-encode [ { if | unless } <condition> ]
http-request normalize-uri fragment-strip [ { if | unless } <condition> ]
http-request normalize-uri path-merge-slashes [ { if | unless } <condition> ]
http-request normalize-uri path-strip-dot [ { if | unless } <condition> ]
http-request normalize-uri path-strip-dotdot [ full ] [ { if | unless } <condition> ]
http-request normalize-uri percent-decode-unreserved [ strict ] [ { if | unless } <condition> ]
http-request normalize-uri percent-to-uppercase [ strict ] [ { if | unless } <condition> ]
http-request normalize-uri query-sort-by-name [ { if | unless } <condition> ]
Performs normalization of the request's URI.
URI normalization in HAProxy 2.4 is currently available as an experimental
technical preview. As such, it requires the global directive
'expose-experimental-directives' first to be able to invoke it. You should be
prepared that the behavior of normalizers might change to fix possible
issues, possibly breaking proper request processing in your infrastructure.
Each normalizer handles a single type of normalization to allow for a
fine-grained selection of the level of normalization that is appropriate for
the supported backend.
As an example the "path-strip-dotdot" normalizer might be useful for a static
fileserver that directly maps the requested URI to the path within the local
filesystem. However it might break routing of an API that expects a specific
number of segments in the path.
It is important to note that some normalizers might result in unsafe
transformations for broken URIs. It might also be possible that a combination
of normalizers that are safe by themselves results in unsafe transformations
when improperly combined.
As an example the "percent-decode-unreserved" normalizer might result in
unexpected results when a broken URI includes bare percent characters. One
such a broken URI is "/%%36%36" which would be decoded to "/%66" which in
turn is equivalent to "/f". By specifying the "strict" option requests to
such a broken URI would safely be rejected.
The following normalizers are available:
- fragment-encode: Encodes "#" as "%23".
The "fragment-strip" normalizer should be preferred, unless it is known
that broken clients do not correctly encode '#' within the path component.
Example:
- /#foo -> /%23foo
- fragment-strip: Removes the URI's "fragment" component.
According to RFC 3986#3.5 the "fragment" component of an URI should not
be sent, but handled by the User Agent after retrieving a resource.
This normalizer should be applied first to ensure that the fragment is
not interpreted as part of the request's path component.
- path-strip-dot: Removes "/./" segments within the "path" component
(RFC 3986#6.2.2.3).
Segments including percent encoded dots ("%2E") will not be detected. Use
the "percent-decode-unreserved" normalizer first if this is undesired.
Example:
- /. -> /
- /./bar/ -> /bar/
- /a/./a -> /a/a
- /.well-known/ -> /.well-known/ (no change)
- path-strip-dotdot: Normalizes "/../" segments within the "path" component
(RFC 3986#6.2.2.3).
This merges segments that attempt to access the parent directory with
their preceding segment.
Empty segments do not receive special treatment. Use the "merge-slashes"
normalizer first if this is undesired.
Segments including percent encoded dots ("%2E") will not be detected. Use
the "percent-decode-unreserved" normalizer first if this is undesired.
Example:
- /foo/../ -> /
- /foo/../bar/ -> /bar/
- /foo/bar/../ -> /foo/
- /../bar/ -> /../bar/
- /bar/../../ -> /../
- /foo//../ -> /foo/
- /foo/%2E%2E/ -> /foo/%2E%2E/
If the "full" option is specified then "../" at the beginning will be
removed as well:
Example:
- /../bar/ -> /bar/
- /bar/../../ -> /
- path-merge-slashes: Merges adjacent slashes within the "path" component
into a single slash.
Example:
- // -> /
- /foo//bar -> /foo/bar
- percent-decode-unreserved: Decodes unreserved percent encoded characters to
their representation as a regular character (RFC 3986#6.2.2.2).
The set of unreserved characters includes all letters, all digits, "-",
".", "_", and "~".
Example:
- /%61dmin -> /admin
- /foo%3Fbar=baz -> /foo%3Fbar=baz (no change)
- /%%36%36 -> /%66 (unsafe)
- /%ZZ -> /%ZZ
If the "strict" option is specified then invalid sequences will result
in a HTTP 400 Bad Request being returned.
Example:
- /%%36%36 -> HTTP 400
- /%ZZ -> HTTP 400
- percent-to-uppercase: Uppercases letters within percent-encoded sequences
(RFC 3986#6.2.2.1).
Example:
- /%6f -> /%6F
- /%zz -> /%zz
If the "strict" option is specified then invalid sequences will result
in a HTTP 400 Bad Request being returned.
Example:
- /%zz -> HTTP 400
- query-sort-by-name: Sorts the query string parameters by parameter name.
Parameters are assumed to be delimited by '&'. Shorter names sort before
longer names and identical parameter names maintain their relative order.
Example:
- /?c=3&a=1&b=2 -> /?a=1&b=2&c=3
- /?aaa=3&a=1&aa=2 -> /?a=1&aa=2&aaa=3
- /?a=3&b=4&a=1&b=5&a=2 -> /?a=3&a=1&a=2&b=4&b=5
http-request redirect <rule> [ { if | unless } <condition> ]
This performs an HTTP redirection based on a redirect rule. This is exactly
the same as the "redirect" statement except that it inserts a redirect rule
which can be processed in the middle of other "http-request" rules and that
these rules use the "log-format" strings. See the "redirect" keyword for the
rule's syntax.
http-request reject [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately closes the connection
without sending any response. It acts similarly to the
"tcp-request content reject" rules. It can be useful to force an immediate
connection closure on HTTP/2 connections.
This matches the value of all occurrences of header field <name> against
<match-regex>. Matching is performed case-sensitively. Matching values are
completely replaced by <replace-fmt>. Format characters are allowed in
<replace-fmt> and work like <fmt> arguments in "http-request add-header".
Standard back-references using the backslash ('\') followed by a number are
supported.
This action acts on whole header lines, regardless of the number of values
they may contain. Thus it is well-suited to process headers naturally
containing commas in their value, such as If-Modified-Since. Headers that
contain a comma-separated list of values, such as Accept, should be processed
using "http-request replace-value".
Example:
http-request replace-header Cookie foo=([^;]*);(.*) foo=\1;ip=%bi;\2
Cookie: foo=foobar; expires=Tue, 14-Jun-2016 01:40:45 GMT;
Cookie: foo=foobar;ip=192.168.1.20; expires=Tue, 14-Jun-2016 01:40:45 GMT;
http-request replace-header User-Agent curl foo
User-Agent: curl/7.47.0
User-Agent: foo
http-request replace-path <match-regex> <replace-fmt> [ { if | unless } <condition> ]
This works like "replace-header" except that it works on the request's path
component instead of a header. The path component starts at the first '/'
after an optional scheme+authority and ends before the question mark. Thus,
the replacement does not modify the scheme, the authority and the
query-string.
It is worth noting that regular expressions may be more expensive to evaluate
than certain ACLs, so rare replacements may benefit from a condition to avoid
performing the evaluation at all if it does not match.
Example:
http-request replace-path (.*) /foo\1
http-request replace-path /foo/(.*) /\1
http-request replace-path /foo/(.*) /\1 if { url_beg /foo/ }
http-request replace-pathq <match-regex> <replace-fmt> [ { if | unless } <condition> ]
This does the same as "http-request replace-path" except that the path
contains the query-string if any is present. Thus, the path and the
query-string are replaced.
Example:
http-request replace-pathq ([^?]*)(\?(.*))? \1/foo\2
http-request replace-uri <match-regex> <replace-fmt> [ { if | unless } <condition> ]
This works like "replace-header" except that it works on the request's URI part
instead of a header. The URI part may contain an optional scheme, authority or
query string. These are considered to be part of the value that is matched
against.
It is worth noting that regular expressions may be more expensive to evaluate
than certain ACLs, so rare replacements may benefit from a condition to avoid
performing the evaluation at all if it does not match.
IMPORTANT NOTE: historically in HTTP/1.x, the vast majority of requests sent
by browsers use the "origin form", which differs from the "absolute form" in
that they do not contain a scheme nor authority in the URI portion. Mostly
only requests sent to proxies, those forged by hand and some emitted by
certain applications use the absolute form. As such, "replace-uri" usually
works fine most of the time in HTTP/1.x with rules starting with a "/". But
with HTTP/2, clients are encouraged to send absolute URIs only, which look
like the ones HTTP/1 clients use to talk to proxies. Such partial replace-uri
rules may then fail in HTTP/2 when they work in HTTP/1. Either the rules need
to be adapted to optionally match a scheme and authority, or replace-path
should be used.
Example:
http-request replace-uri ^http://(.*) https://\1
http-request replace-uri ([^/:]*://[^/]*)?(.*) \1/foo\2
http-request replace-value <name> <match-regex> <replace-fmt> [ { if | unless } <condition> ]
This works like "replace-header" except that it matches the regex against
every comma-delimited value of the header field <name> instead of the
entire header. This is suited for all headers which are allowed to carry
more than one value. An example could be the Accept header.
Example:
http-request replace-value X-Forwarded-For ^192\.168\.(.*)$ 172.16.\1
X-Forwarded-For: 192.168.10.1, 192.168.13.24, 10.0.0.37
X-Forwarded-For: 172.16.10.1, 172.16.13.24, 10.0.0.37
http-request return [status <code>] [content-type <type>] [ { default-errorfiles | errorfile <file> | errorfiles <name> | file <file> | lf-file <file> | string <str> | lf-string <fmt> } ] [ hdr <name> <fmt> ]* [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately returns a response. The
default status code used for the response is 200. It can be optionally
specified as an arguments to "status". The response content-type may also be
specified as an argument to "content-type". Finally the response itself may
be defined. It can be a full HTTP response specifying the errorfile to use,
or the response payload specifying the file or the string to use. These rules
are followed to create the response :
* If neither the errorfile nor the payload to use is defined, a dummy
response is returned. Only the "status" argument is considered. It can be
any code in the range [200, 599]. The "content-type" argument, if any, is
ignored.
* If "default-errorfiles" argument is set, the proxy's errorfiles are
considered. If the "status" argument is defined, it must be one of the
status code handled by HAProxy (200, 400, 403, 404, 405, 408, 410, 413,
425, 429, 500, 501, 502, 503, and 504). The "content-type" argument, if
any, is ignored.
* If a specific errorfile is defined, with an "errorfile" argument, the
corresponding file, containing a full HTTP response, is returned. Only the
"status" argument is considered. It must be one of the status code handled
by HAProxy (200, 400, 403, 404, 405, 408, 410, 413, 425, 429, 500, 501,
502, 503, and 504). The "content-type" argument, if any, is ignored.
* If an http-errors section is defined, with an "errorfiles" argument, the
corresponding file in the specified http-errors section, containing a full
HTTP response, is returned. Only the "status" argument is considered. It
must be one of the status code handled by HAProxy (200, 400, 403, 404, 405,
408, 410, 413, 425, 429, 500, 501, 502, 503, and 504). The "content-type"
argument, if any, is ignored.
* If a "file" or a "lf-file" argument is specified, the file's content is
used as the response payload. If the file is not empty, its content-type
must be set as argument to "content-type". Otherwise, any "content-type"
argument is ignored. With a "lf-file" argument, the file's content is
evaluated as a log-format string. With a "file" argument, it is considered
as a raw content.
* If a "string" or "lf-string" argument is specified, the defined string is
used as the response payload. The content-type must always be set as
argument to "content-type". With a "lf-string" argument, the string is
evaluated as a log-format string. With a "string" argument, it is
considered as a raw string.
When the response is not based on an errorfile, it is possible to append HTTP
header fields to the response using "hdr" arguments. Otherwise, all "hdr"
arguments are ignored. For each one, the header name is specified in <name>
and its value is defined by <fmt> which follows the log-format rules.
Note that the generated response must be smaller than a buffer. And to avoid
any warning, when an errorfile or a raw file is loaded, the buffer space
reserved for the headers rewriting should also be free.
No further "http-request" rules are evaluated.
Example:
http-request return errorfile /etc/haproxy/errorfiles/200.http \
if { path /ping }
http-request return content-type image/x-icon file /var/www/favicon.ico \
if { path /favicon.ico }
http-request return status 403 content-type text/plain \
lf-string "Access denied. IP %[src] is blacklisted." \
if { src -f /etc/haproxy/blacklist.lst }
http-request sc-inc-gpc0(<sc-id>) [ { if | unless } <condition> ]
http-request sc-inc-gpc1(<sc-id>) [ { if | unless } <condition> ]
This actions increments the GPC0 or GPC1 counter according with the sticky
counter designated by <sc-id>. If an error occurs, this action silently fails
and the actions evaluation continues.
http-request sc-set-gpt0(<sc-id>) { <int> | <expr> } [ { if | unless } <condition> ]
This action sets the 32-bit unsigned GPT0 tag according to the sticky counter
designated by <sc-id> and the value of <int>/<expr>. The expected result is a
boolean. If an error occurs, this action silently fails and the actions
evaluation continues.
http-request set-dst <expr> [ { if | unless } <condition> ]
This is used to set the destination IP address to the value of specified
expression. Useful when a proxy in front of HAProxy rewrites destination IP,
but provides the correct IP in a HTTP header; or you want to mask the IP for
privacy. If you want to connect to the new address/port, use '0.0.0.0:0' as a
server address in the backend.
Arguments:<expr> Is a standard HAProxy expression formed by a sample-fetch followed
by some converters.
Example:
http-request set-dst hdr(x-dst)
http-request set-dst dst,ipmask(24)
When possible, set-dst preserves the original destination port as long as the
address family allows it, otherwise the destination port is set to 0.
http-request set-dst-port <expr> [ { if | unless } <condition> ]
This is used to set the destination port address to the value of specified
expression. If you want to connect to the new address/port, use '0.0.0.0:0'
as a server address in the backend.
Arguments:<expr> Is a standard HAProxy expression formed by a sample-fetch
followed by some converters.
Example:
http-request set-dst-port hdr(x-port)
http-request set-dst-port int(4000)
When possible, set-dst-port preserves the original destination address as
long as the address family supports a port, otherwise it forces the
destination address to IPv4 "0.0.0.0" before rewriting the port.
This does the same as "http-request add-header" except that the header name
is first removed if it existed. This is useful when passing security
information to the server, where the header must not be manipulated by
external users. Note that the new value is computed before the removal so it
is possible to concatenate a value to an existing header.
Example:
http-request set-header X-Haproxy-Current-Date %T
http-request set-header X-SSL %[ssl_fc]
http-request set-header X-SSL-Session_ID %[ssl_fc_session_id,hex]
http-request set-header X-SSL-Client-Verify %[ssl_c_verify]
http-request set-header X-SSL-Client-DN %{+Q}[ssl_c_s_dn]
http-request set-header X-SSL-Client-CN %{+Q}[ssl_c_s_dn(cn)]
http-request set-header X-SSL-Issuer %{+Q}[ssl_c_i_dn]
http-request set-header X-SSL-Client-NotBefore %{+Q}[ssl_c_notbefore]
http-request set-header X-SSL-Client-NotAfter %{+Q}[ssl_c_notafter]
http-request set-log-level <level> [ { if | unless } <condition> ]
This is used to change the log level of the current request when a certain
condition is met. Valid levels are the 8 syslog levels (see the "log"
keyword) plus the special level "silent" which disables logging for this
request. This rule is not final so the last matching rule wins. This rule
can be useful to disable health checks coming from another equipment.
http-request set-map(<file-name>) <key fmt> <value fmt> [ { if | unless } <condition> ]
This is used to add a new entry into a MAP. The MAP must be loaded from a
file (even a dummy empty file). The file name of the MAP to be updated is
passed between parentheses. It takes 2 arguments: <key fmt>, which follows
log-format rules, used to collect MAP key, and <value fmt>, which follows
log-format rules, used to collect content for the new entry.
It performs a lookup in the MAP before insertion, to avoid duplicated (or
more) values. This lookup is done by a linear search and can be expensive
with large lists! It is the equivalent of the "set map" command from the
stats socket, but can be triggered by an HTTP request.
http-request set-mark <mark> [ { if | unless } <condition> ]
This is used to set the Netfilter MARK on all packets sent to the client to
the value passed in <mark> on platforms which support it. This value is an
unsigned 32 bit value which can be matched by netfilter and by the routing
table. It can be expressed both in decimal or hexadecimal format (prefixed by
"0x"). This can be useful to force certain packets to take a different route
(for example a cheaper network path for bulk downloads). This works on Linux
kernels 2.6.32 and above and requires admin privileges.
http-request set-method <fmt> [ { if | unless } <condition> ]
This rewrites the request method with the result of the evaluation of format
string <fmt>. There should be very few valid reasons for having to do so as
this is more likely to break something than to fix it.
http-request set-nice <nice> [ { if | unless } <condition> ]
This sets the "nice" factor of the current request being processed. It only
has effect against the other requests being processed at the same time.
The default value is 0, unless altered by the "nice" setting on the "bind"
line. The accepted range is -1024..1024. The higher the value, the nicest
the request will be. Lower values will make the request more important than
other ones. This can be useful to improve the speed of some requests, or
lower the priority of non-important requests. Using this setting without
prior experimentation can cause some major slowdown.
http-request set-path <fmt> [ { if | unless } <condition> ]
This rewrites the request path with the result of the evaluation of format
string <fmt>. The query string, if any, is left intact. If a scheme and
authority is found before the path, they are left intact as well. If the
request doesn't have a path ("*"), this one is replaced with the format.
This can be used to prepend a directory component in front of a path for
example. See also "http-request set-query" and "http-request set-uri".
Example :
http-request set-path /%[hdr(host)]%[path]
http-request set-pathq <fmt> [ { if | unless } <condition> ]
This does the same as "http-request set-path" except that the query-string is
also rewritten. It may be used to remove the query-string, including the
question mark (it is not possible using "http-request set-query").
http-request set-priority-class <expr> [ { if | unless } <condition> ]
This is used to set the queue priority class of the current request.
The value must be a sample expression which converts to an integer in the
range -2047..2047. Results outside this range will be truncated.
The priority class determines the order in which queued requests are
processed. Lower values have higher priority.
http-request set-priority-offset <expr> [ { if | unless } <condition> ]
This is used to set the queue priority timestamp offset of the current
request. The value must be a sample expression which converts to an integer
in the range -524287..524287. Results outside this range will be truncated.
When a request is queued, it is ordered first by the priority class, then by
the current timestamp adjusted by the given offset in milliseconds. Lower
values have higher priority.
Note that the resulting timestamp is is only tracked with enough precision
for 524,287ms (8m44s287ms). If the request is queued long enough to where the
adjusted timestamp exceeds this value, it will be misidentified as highest
priority. Thus it is important to set "timeout queue" to a value, where when
combined with the offset, does not exceed this limit.
http-request set-query <fmt> [ { if | unless } <condition> ]
This rewrites the request's query string which appears after the first
question mark ("?") with the result of the evaluation of format string <fmt>.
The part prior to the question mark is left intact. If the request doesn't
contain a question mark and the new value is not empty, then one is added at
the end of the URI, followed by the new value. If a question mark was
present, it will never be removed even if the value is empty. This can be
used to add or remove parameters from the query string.
See also "http-request set-query" and "http-request set-uri".
Example:
http-request set-query %[query,regsub(%3D,=,g)]
http-request set-src <expr> [ { if | unless } <condition> ]
This is used to set the source IP address to the value of specified
expression. Useful when a proxy in front of HAProxy rewrites source IP, but
provides the correct IP in a HTTP header; or you want to mask source IP for
privacy. All subsequent calls to "src" fetch will return this value
(see example).
Arguments :<expr> Is a standard HAProxy expression formed by a sample-fetch followed
by some converters.
See also "option forwardfor".
Example:
http-request set-src hdr(x-forwarded-for)
http-request set-src src,ipmask(24)
http-request track-sc0 src
When possible, set-src preserves the original source port as long as the
address family allows it, otherwise the source port is set to 0.
http-request set-src-port <expr> [ { if | unless } <condition> ]
This is used to set the source port address to the value of specified
expression.
Arguments:<expr> Is a standard HAProxy expression formed by a sample-fetch followed
by some converters.
Example:
http-request set-src-port hdr(x-port)
http-request set-src-port int(4000)
When possible, set-src-port preserves the original source address as long as
the address family supports a port, otherwise it forces the source address to
IPv4 "0.0.0.0" before rewriting the port.
http-request set-timeout { server | tunnel } { <timeout> | <expr> } [ { if | unless } <condition> ]
This action overrides the specified "server" or "tunnel" timeout for the
current stream only. The timeout can be specified in millisecond or with any
other unit if the number is suffixed by the unit as explained at the top of
this document. It is also possible to write an expression which must returns
a number interpreted as a timeout in millisecond.
Note that the server/tunnel timeouts are only relevant on the backend side
and thus this rule is only available for the proxies with backend
capabilities. Also the timeout value must be non-null to obtain the expected
results.
Example:
http-request set-timeout tunnel 5s
http-request set-timeout server req.hdr(host),map_int(host.lst)
http-request set-tos <tos> [ { if | unless } <condition> ]
This is used to set the TOS or DSCP field value of packets sent to the client
to the value passed in <tos> on platforms which support this. This value
represents the whole 8 bits of the IP TOS field, and can be expressed both in
decimal or hexadecimal format (prefixed by "0x"). Note that only the 6 higher
bits are used in DSCP or TOS, and the two lower bits are always 0. This can
be used to adjust some routing behavior on border routers based on some
information from the request.
See RFC 2474, 2597, 3260 and 4594 for more information.
http-request set-uri <fmt> [ { if | unless } <condition> ]
This rewrites the request URI with the result of the evaluation of format
string <fmt>. The scheme, authority, path and query string are all replaced
at once. This can be used to rewrite hosts in front of proxies, or to
perform complex modifications to the URI such as moving parts between the
path and the query string.
See also "http-request set-path" and "http-request set-query".
http-request set-var(<var-name>) <expr> [ { if | unless } <condition> ]
This is used to set the contents of a variable. The variable is declared
inline.
Arguments:<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed are:
"proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction
(request and response)
"req" : the variable is shared only during request
processing
"res" : the variable is shared only during response
processing
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9'
and '_'.
<expr> Is a standard HAProxy expression formed by a sample-fetch
followed by some converters.
Example:
http-request set-var(req.my_var) req.fhdr(user-agent),lower
http-request send-spoe-group <engine-name> <group-name> [ { if | unless } <condition> ]
This action is used to trigger sending of a group of SPOE messages. To do so,
the SPOE engine used to send messages must be defined, as well as the SPOE
group to send. Of course, the SPOE engine must refer to an existing SPOE
filter. If not engine name is provided on the SPOE filter line, the SPOE
agent name must be used.
Arguments:<engine-name> The SPOE engine name.
<group-name> The SPOE group name as specified in the engine
configuration.
http-request silent-drop [ { if | unless } <condition> ]
This stops the evaluation of the rules and makes the client-facing connection
suddenly disappear using a system-dependent way that tries to prevent the
client from being notified. The effect it then that the client still sees an
established connection while there's none on HAProxy. The purpose is to
achieve a comparable effect to "tarpit" except that it doesn't use any local
resource at all on the machine running HAProxy. It can resist much higher
loads than "tarpit", and slow down stronger attackers. It is important to
understand the impact of using this mechanism. All stateful equipment placed
between the client and HAProxy (firewalls, proxies, load balancers) will also
keep the established connection for a long time and may suffer from this
action.
On modern Linux systems running with enough privileges, the TCP_REPAIR socket
option is used to block the emission of a TCP reset. On other systems, the
socket's TTL is reduced to 1 so that the TCP reset doesn't pass the first
router, though it's still delivered to local networks. Do not use it unless
you fully understand how it works.
http-request strict-mode { on | off }
This enables or disables the strict rewriting mode for following rules. It
does not affect rules declared before it and it is only applicable on rules
performing a rewrite on the requests. When the strict mode is enabled, any
rewrite failure triggers an internal error. Otherwise, such errors are
silently ignored. The purpose of the strict rewriting mode is to make some
rewrites optional while others must be performed to continue the request
processing.
By default, the strict rewriting mode is enabled. Its value is also reset
when a ruleset evaluation ends. So, for instance, if you change the mode on
the frontend, the default mode is restored when HAProxy starts the backend
rules evaluation.
http-request tarpit [deny_status <status>] [ { if | unless } <condition> ]
http-request tarpit [ { status | deny_status } <code>] [content-type <type>] [ { default-errorfiles | errorfile <file> | errorfiles <name> | file <file> | lf-file <file> | string <str> | lf-string <fmt> } ] [ hdr <name> <fmt> ]* [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately blocks the request
without responding for a delay specified by "timeout tarpit" or
"timeout connect" if the former is not set. After that delay, if the client
is still connected, a response is returned so that the client does not
suspect it has been tarpitted. Logs will report the flags "PT". The goal of
the tarpit rule is to slow down robots during an attack when they're limited
on the number of concurrent requests. It can be very efficient against very
dumb robots, and will significantly reduce the load on firewalls compared to
a "deny" rule. But when facing "correctly" developed robots, it can make
things worse by forcing HAProxy and the front firewall to support insane
number of concurrent connections. By default an HTTP error 500 is returned.
But the response may be customized using same syntax than
"http-request return" rules. Thus, see "http-request return" for details.
For compatibility purpose, when no argument is defined, or only "deny_status",
the argument "default-errorfiles" is implied. It means
"http-request tarpit [deny_status <status>]" is an alias of
"http-request tarpit [status <status>] default-errorfiles".
No further "http-request" rules are evaluated.
See also "http-request return" and "http-request silent-drop".
http-request track-sc0 <key> [table <table>] [ { if | unless } <condition> ]
http-request track-sc1 <key> [table <table>] [ { if | unless } <condition> ]
http-request track-sc2 <key> [table <table>] [ { if | unless } <condition> ]
This enables tracking of sticky counters from current request. These rules do
not stop evaluation and do not change default action. The number of counters
that may be simultaneously tracked by the same connection is set in
MAX_SESS_STKCTR at build time (reported in haproxy -vv) which defaults to 3,
so the track-sc number is between 0 and (MAX_SESS_STKCTR-1). The first
"track-sc0" rule executed enables tracking of the counters of the specified
table as the first set. The first "track-sc1" rule executed enables tracking
of the counters of the specified table as the second set. The first
"track-sc2" rule executed enables tracking of the counters of the specified
table as the third set. It is a recommended practice to use the first set of
counters for the per-frontend counters and the second set for the per-backend
ones. But this is just a guideline, all may be used everywhere.
Arguments :<key> is mandatory, and is a sample expression rule as described in
section 7.3. It describes what elements of the incoming request or
connection will be analyzed, extracted, combined, and used to
select which table entry to update the counters.
<table> is an optional table to be used instead of the default one, which
is the stick-table declared in the current proxy. All the counters
for the matches and updates for the key will then be performed in
that table until the session ends.
Once a "track-sc*" rule is executed, the key is looked up in the table and if
it is not found, an entry is allocated for it. Then a pointer to that entry
is kept during all the session's life, and this entry's counters are updated
as often as possible, every time the session's counters are updated, and also
systematically when the session ends. Counters are only updated for events
that happen after the tracking has been started. As an exception, connection
counters and request counters are systematically updated so that they reflect
useful information.
If the entry tracks concurrent connection counters, one connection is counted
for as long as the entry is tracked, and the entry will not expire during
that time. Tracking counters also provides a performance advantage over just
checking the keys, because only one table lookup is performed for all ACL
checks that make use of it.
http-request unset-var(<var-name>) [ { if | unless } <condition> ]
This is used to unset a variable. See above for details about <var-name>.
Example:
http-request unset-var(req.my_var)
http-request use-service <service-name> [ { if | unless } <condition> ]
This directive executes the configured HTTP service to reply to the request
and stops the evaluation of the rules. An HTTP service may choose to reply by
sending any valid HTTP response or it may immediately close the connection
without sending any response. Outside natives services, for instance the
Prometheus exporter, it is possible to write your own services in Lua. No
further "http-request" rules are evaluated.
Arguments :<service-name> is mandatory. It is the service to call
Example:
http-request use-service prometheus-exporter if { path /metrics }
http-request wait-for-body time <time> [ at-least <bytes> ] [ { if | unless } <condition> ]
This will delay the processing of the request waiting for the payload for at
most <time> milliseconds. if "at-least" argument is specified, HAProxy stops
to wait the payload when the first <bytes> bytes are received. 0 means no
limit, it is the default value. Regardless the "at-least" argument value,
HAProxy stops to wait if the whole payload is received or if the request
buffer is full. This action may be used as a replacement to "option
http-buffer-request".
Arguments :<time> is mandatory. It is the maximum time to wait for the body. It
follows the HAProxy time format and is expressed in milliseconds.
<bytes> is optional. It is the minimum payload size to receive to stop to
wait. It follows the HAProxy size format and is expressed in
bytes.
Example:
http-request wait-for-body time 1s at-least 1k if METH_POST
See also : "
option http-buffer-request"
http-request wait-for-handshake [ { if | unless } <condition> ]
This will delay the processing of the request until the SSL handshake
happened. This is mostly useful to delay processing early data until we're
sure they are valid.
http-response <action> <options...> [ { if | unless } <condition> ]
Access control for Layer 7 responses
May be used in sections :
defaults |
frontend |
listen |
backend |
The http-response statement defines a set of rules which apply to layer 7
processing. The rules are evaluated in their declaration order when they are
met in a frontend, listen or backend section. Any rule may optionally be
followed by an ACL-based condition, in which case it will only be evaluated
if the condition is true. Since these rules apply on responses, the backend
rules are applied first, followed by the frontend's rules.
The first keyword is the rule's action. The supported actions are described
below.
There is no limit to the number of http-response statements per instance.
Example:
acl key_acl res.hdr(X-Acl-Key) -m found
acl myhost hdr(Host) -f myhost.lst
http-response add-acl(myhost.lst) %[res.hdr(X-Acl-Key)] if key_acl
http-response del-acl(myhost.lst) %[res.hdr(X-Acl-Key)] if key_acl
Example:
acl value res.hdr(X-Value) -m found
use_backend bk_appli if { hdr(Host),map_str(map.lst) -m found }
http-response set-map(map.lst) %[src] %[res.hdr(X-Value)] if value
http-response del-map(map.lst) %[src] if ! value
See also : "
http-request",
section 3.4 about userlists and
section 7 about ACL usage.
http-response add-acl(<file-name>) <key fmt> [ { if | unless } <condition> ]
This is used to add a new entry into an ACL. The ACL must be loaded from a
file (even a dummy empty file). The file name of the ACL to be updated is
passed between parentheses. It takes one argument: <key fmt>, which follows
log-format rules, to collect content of the new entry. It performs a lookup
in the ACL before insertion, to avoid duplicated (or more) values.
This lookup is done by a linear search and can be expensive with large lists!
It is the equivalent of the "add acl" command from the stats socket, but can
be triggered by an HTTP response.
This appends an HTTP header field whose name is specified in <name> and whose
value is defined by <fmt> which follows the log-format rules (see Custom Log
Format in section 8.2.4). This may be used to send a cookie to a client for
example, or to pass some internal information.
This rule is not final, so it is possible to add other similar rules.
Note that header addition is performed immediately, so one rule might reuse
the resulting header from a previous rule.
http-response allow [ { if | unless } <condition> ]
This stops the evaluation of the rules and lets the response pass the check.
No further "http-response" rules are evaluated for the current section.
http-response cache-store <name> [ { if | unless } <condition> ]
See section 6.2 about cache setup.
http-response capture <sample> id <id> [ { if | unless } <condition> ]
This captures sample expression <sample> from the response buffer, and
converts it to a string. The resulting string is stored into the next request
"capture" slot, so it will possibly appear next to some captured HTTP
headers. It will then automatically appear in the logs, and it will be
possible to extract it using sample fetch rules to feed it into headers or
anything. Please check section 7.3 (Fetching samples) and
"capture response header" for more information.
The keyword "id" is the id of the capture slot which is used for storing the
string. The capture slot must be defined in an associated frontend.
This is useful to run captures in backends. The slot id can be declared by a
previous directive "http-response capture" or with the "declare capture"
keyword.
When using this action in a backend, double check that the relevant
frontend(s) have the required capture slots otherwise, this rule will be
ignored at run time. This can't be detected at configuration parsing time
due to HAProxy's ability to dynamically resolve backend name at runtime.
http-response del-acl(<file-name>) <key fmt> [ { if | unless } <condition> ]
This is used to delete an entry from an ACL. The ACL must be loaded from a
file (even a dummy empty file). The file name of the ACL to be updated is
passed between parentheses. It takes one argument: <key fmt>, which follows
log-format rules, to collect content of the entry to delete.
It is the equivalent of the "del acl" command from the stats socket, but can
be triggered by an HTTP response.
This removes all HTTP header fields whose name is specified in <name>. <meth>
is the matching method, applied on the header name. Supported matching methods
are "str" (exact match), "beg" (prefix match), "end" (suffix match), "sub"
(substring match) and "reg" (regex match). If not specified, exact matching
method is used.
http-response del-map(<file-name>) <key fmt> [ { if | unless } <condition> ]
This is used to delete an entry from a MAP. The MAP must be loaded from a
file (even a dummy empty file). The file name of the MAP to be updated is
passed between parentheses. It takes one argument: <key fmt>, which follows
log-format rules, to collect content of the entry to delete.
It takes one argument: "file name" It is the equivalent of the "del map"
command from the stats socket, but can be triggered by an HTTP response.
http-response deny [deny_status <status>] [ { if | unless } <condition> ]
http-response deny [ { status | deny_status } <code>] [content-type <type>] [ { default-errorfiles | errorfile <file> | errorfiles <name> | file <file> | lf-file <file> | string <str> | lf-string <fmt> } ] [ hdr <name> <fmt> ]* [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately rejects the response.
By default an HTTP 502 error is returned. But the response may be customized
using same syntax than "http-response return" rules. Thus, see
"http-response return" for details. For compatibility purpose, when no
argument is defined, or only "deny_status", the argument "default-errorfiles"
is implied. It means "http-response deny [deny_status <status>]" is an alias
of "http-response deny [status <status>] default-errorfiles".
No further "http-response" rules are evaluated.
See also "http-response return".
http-response redirect <rule> [ { if | unless } <condition> ]
This performs an HTTP redirection based on a redirect rule.
This supports a format string similarly to "http-request redirect" rules,
with the exception that only the "location" type of redirect is possible on
the response. See the "redirect" keyword for the rule's syntax. When a
redirect rule is applied during a response, connections to the server are
closed so that no data can be forwarded from the server to the client.
This works like "http-request replace-header" except that it works on the
server's response instead of the client's request.
Example:
http-response replace-header Set-Cookie (C=[^;]*);(.*) \1;ip=%bi;\2
Set-Cookie: C=1; expires=Tue, 14-Jun-2016 01:40:45 GMT
Set-Cookie: C=1;ip=192.168.1.20; expires=Tue, 14-Jun-2016 01:40:45 GMT
http-response replace-value <name> <regex-match> <replace-fmt> [ { if | unless } <condition> ]
This works like "http-request replace-value" except that it works on the
server's response instead of the client's request.
Example:
http-response replace-value Cache-control ^public$ private
Cache-Control: max-age=3600, public
Cache-Control: max-age=3600, private
http-response return [status <code>] [content-type <type>] [ { default-errorfiles | errorfile <file> | errorfiles <name> | file <file> | lf-file <file> | string <str> | lf-string <fmt> } ] [ hdr <name> <value> ]* [ { if | unless } <condition> ]
This stops the evaluation of the rules and immediately returns a response. The
default status code used for the response is 200. It can be optionally
specified as an arguments to "status". The response content-type may also be
specified as an argument to "content-type". Finally the response itself may
be defined. If can be a full HTTP response specifying the errorfile to use,
or the response payload specifying the file or the string to use. These rules
are followed to create the response :
* If neither the errorfile nor the payload to use is defined, a dummy
response is returned. Only the "status" argument is considered. It can be
any code in the range [200, 599]. The "content-type" argument, if any, is
ignored.
* If "default-errorfiles" argument is set, the proxy's errorfiles are
considered. If the "status" argument is defined, it must be one of the
status code handled by HAProxy (200, 400, 403, 404, 405, 408, 410, 413,
425, 429, 500, 501, 502, 503, and 504). The "content-type" argument, if
any, is ignored.
* If a specific errorfile is defined, with an "errorfile" argument, the
corresponding file, containing a full HTTP response, is returned. Only the
"status" argument is considered. It must be one of the status code handled
by HAProxy (200, 400, 403, 404, 405, 408, 410, 413, 425, 429, 500, 501,
502, 503, and 504). The "content-type" argument, if any, is ignored.
* If an http-errors section is defined, with an "errorfiles" argument, the
corresponding file in the specified http-errors section, containing a full
HTTP response, is returned. Only the "status" argument is considered. It
must be one of the status code handled by HAProxy (200, 400, 403, 404, 405,
408, 410, 413, 425, 429, 500, 501, 502, 503, and 504). The "content-type"
argument, if any, is ignored.
* If a "file" or a "lf-file" argument is specified, the file's content is
used as the response payload. If the file is not empty, its content-type
must be set as argument to "content-type". Otherwise, any "content-type"
argument is ignored. With a "lf-file" argument, the file's content is
evaluated as a log-format string. With a "file" argument, it is considered
as a raw content.
* If a "string" or "lf-string" argument is specified, the defined string is
used as the response payload. The content-type must always be set as
argument to "content-type". With a "lf-string" argument, the string is
evaluated as a log-format string. With a "string" argument, it is
considered as a raw string.
When the response is not based an errorfile, it is possible to appends HTTP
header fields to the response using "hdr" arguments. Otherwise, all "hdr"
arguments are ignored. For each one, the header name is specified in <name>
and its value is defined by <fmt> which follows the log-format rules.
Note that the generated response must be smaller than a buffer. And to avoid
any warning, when an errorfile or a raw file is loaded, the buffer space
reserved to the headers rewriting should also be free.
No further "http-response" rules are evaluated.
Example:
http-response return errorfile /etc/haproxy/errorfiles/200.http \
if { status eq 404 }
http-response return content-type text/plain \
string "This is the end !" \
if { status eq 500 }
http-response sc-inc-gpc0(<sc-id>) [ { if | unless } <condition> ]
http-response sc-inc-gpc1(<sc-id>) [ { if | unless } <condition> ]
This action increments the GPC0 or GPC1 counter according with the sticky
counter designated by <sc-id>. If an error occurs, this action silently fails
and the actions evaluation continues.
http-response sc-set-gpt0(<sc-id>) { <int> | <expr> } [ { if | unless } <condition> ]
This action sets the 32-bit unsigned GPT0 tag according to the sticky counter
designated by <sc-id> and the value of <int>/<expr>. The expected result is a
boolean. If an error occurs, this action silently fails and the actions
evaluation continues.
http-response send-spoe-group [ { if | unless } <condition> ]
This action is used to trigger sending of a group of SPOE messages. To do so,
the SPOE engine used to send messages must be defined, as well as the SPOE
group to send. Of course, the SPOE engine must refer to an existing SPOE
filter. If not engine name is provided on the SPOE filter line, the SPOE
agent name must be used.
Arguments:<engine-name> The SPOE engine name.
<group-name> The SPOE group name as specified in the engine
configuration.
This does the same as "add-header" except that the header name is first
removed if it existed. This is useful when passing security information to
the server, where the header must not be manipulated by external users.
http-response set-log-level <level> [ { if | unless } <condition> ]
This is used to change the log level of the current request when a certain
condition is met. Valid levels are the 8 syslog levels (see the "log"
keyword) plus the special level "silent" which disables logging for this
request. This rule is not final so the last matching rule wins. This rule can
be useful to disable health checks coming from another equipment.
http-response set-map(<file-name>) <key fmt> <value fmt>
This is used to add a new entry into a MAP. The MAP must be loaded from a
file (even a dummy empty file). The file name of the MAP to be updated is
passed between parentheses. It takes 2 arguments: <key fmt>, which follows
log-format rules, used to collect MAP key, and <value fmt>, which follows
log-format rules, used to collect content for the new entry. It performs a
lookup in the MAP before insertion, to avoid duplicated (or more) values.
This lookup is done by a linear search and can be expensive with large lists!
It is the equivalent of the "set map" command from the stats socket, but can
be triggered by an HTTP response.
http-response set-mark <mark> [ { if | unless } <condition> ]
This is used to set the Netfilter MARK on all packets sent to the client to
the value passed in <mark> on platforms which support it. This value is an
unsigned 32 bit value which can be matched by netfilter and by the routing
table. It can be expressed both in decimal or hexadecimal format (prefixed
by "0x"). This can be useful to force certain packets to take a different
route (for example a cheaper network path for bulk downloads). This works on
Linux kernels 2.6.32 and above and requires admin privileges.
http-response set-nice <nice> [ { if | unless } <condition> ]
This sets the "nice" factor of the current request being processed.
It only has effect against the other requests being processed at the same
time. The default value is 0, unless altered by the "nice" setting on the
"bind" line. The accepted range is -1024..1024. The higher the value, the
nicest the request will be. Lower values will make the request more important
than other ones. This can be useful to improve the speed of some requests, or
lower the priority of non-important requests. Using this setting without
prior experimentation can cause some major slowdown.
http-response set-status <status> [reason <str>] [ { if | unless } <condition> ]
This replaces the response status code with <status> which must be an integer
between 100 and 999. Optionally, a custom reason text can be provided defined
by <str>, or the default reason for the specified code will be used as a
fallback.
Example:
http-response set-status 431
http-response set-status 503 reason "Slow Down".
http-response set-tos <tos> [ { if | unless } <condition> ]
This is used to set the TOS or DSCP field value of packets sent to the client
to the value passed in <tos> on platforms which support this.
This value represents the whole 8 bits of the IP TOS field, and can be
expressed both in decimal or hexadecimal format (prefixed by "0x"). Note that
only the 6 higher bits are used in DSCP or TOS, and the two lower bits are
always 0. This can be used to adjust some routing behavior on border routers
based on some information from the request.
See RFC 2474, 2597, 3260 and 4594 for more information.
http-response set-var(<var-name>) <expr> [ { if | unless } <condition> ]
This is used to set the contents of a variable. The variable is declared
inline.
Arguments:<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed are:
"proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction
(request and response)
"req" : the variable is shared only during request
processing
"res" : the variable is shared only during response
processing
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.'
and '_'.
<expr> Is a standard HAProxy expression formed by a sample-fetch
followed by some converters.
Example:
http-response set-var(sess.last_redir) res.hdr(location)
http-response silent-drop [ { if | unless } <condition> ]
This stops the evaluation of the rules and makes the client-facing connection
suddenly disappear using a system-dependent way that tries to prevent the
client from being notified. The effect it then that the client still sees an
established connection while there's none on HAProxy. The purpose is to
achieve a comparable effect to "tarpit" except that it doesn't use any local
resource at all on the machine running HAProxy. It can resist much higher
loads than "tarpit", and slow down stronger attackers. It is important to
understand the impact of using this mechanism. All stateful equipment placed
between the client and HAProxy (firewalls, proxies, load balancers) will also
keep the established connection for a long time and may suffer from this
action.
On modern Linux systems running with enough privileges, the TCP_REPAIR socket
option is used to block the emission of a TCP reset. On other systems, the
socket's TTL is reduced to 1 so that the TCP reset doesn't pass the first
router, though it's still delivered to local networks. Do not use it unless
you fully understand how it works.
http-response strict-mode { on | off }
This enables or disables the strict rewriting mode for following rules. It
does not affect rules declared before it and it is only applicable on rules
performing a rewrite on the responses. When the strict mode is enabled, any
rewrite failure triggers an internal error. Otherwise, such errors are
silently ignored. The purpose of the strict rewriting mode is to make some
rewrites optional while others must be performed to continue the response
processing.
By default, the strict rewriting mode is enabled. Its value is also reset
when a ruleset evaluation ends. So, for instance, if you change the mode on
the backend, the default mode is restored when HAProxy starts the frontend
rules evaluation.
http-response track-sc0 <key> [table <table>] [ { if | unless } <condition> ]
http-response track-sc1 <key> [table <table>] [ { if | unless } <condition> ]
http-response track-sc2 <key> [table <table>] [ { if | unless } <condition> ]
This enables tracking of sticky counters from current response. Please refer
to "http-request track-sc" for a complete description. The only difference
from "http-request track-sc" is the <key> sample expression can only make use
of samples in response (e.g. res.*, status etc.) and samples below Layer 6
(e.g. SSL-related samples, see section 7.3.4). If the sample is not
supported, HAProxy will fail and warn while parsing the config.
http-response unset-var(<var-name>) [ { if | unless } <condition> ]
This is used to unset a variable. See "http-response set-var" for details
about <var-name>.
Example:
http-response unset-var(sess.last_redir)
http-response wait-for-body time <time> [ at-least <bytes> ] [ { if | unless } <condition> ]
This will delay the processing of the response waiting for the payload for at
most <time> milliseconds. if "at-least" argument is specified, HAProxy stops
to wait the payload when the first <bytes> bytes are received. 0 means no
limit, it is the default value. Regardless the "at-least" argument value,
HAProxy stops to wait if the whole payload is received or if the response
buffer is full.
Arguments :<time> is mandatory. It is the maximum time to wait for the body. It
follows the HAProxy time format and is expressed in milliseconds.
<bytes> is optional. It is the minimum payload size to receive to stop to
wait. It follows the HAProxy size format and is expressed in
bytes.
Example:
http-response wait-for-body time 1s at-least 10k
http-reuse { never | safe | aggressive | always }
Declare how idle HTTP connections may be shared between requests
May be used in sections :
defaults |
frontend |
listen |
backend |
By default, a connection established between HAProxy and the backend server
which is considered safe for reuse is moved back to the server's idle
connections pool so that any other request can make use of it. This is the
"safe" strategy below.
The argument indicates the desired connection reuse strategy :
- "never" : idle connections are never shared between sessions. This mode
may be enforced to cancel a different strategy inherited from
a defaults section or for troubleshooting. For example, if an
old bogus application considers that multiple requests over
the same connection come from the same client and it is not
possible to fix the application, it may be desirable to
disable connection sharing in a single backend. An example of
such an application could be an old HAProxy using cookie
insertion in tunnel mode and not checking any request past the
first one.
- "safe" : this is the default and the recommended strategy. The first
request of a session is always sent over its own connection,
and only subsequent requests may be dispatched over other
existing connections. This ensures that in case the server
closes the connection when the request is being sent, the
browser can decide to silently retry it. Since it is exactly
equivalent to regular keep-alive, there should be no side
effects. There is also a special handling for the connections
using protocols subject to Head-of-line blocking (backend with
h2 or fcgi). In this case, when at least one stream is
processed, the used connection is reserved to handle streams
of the same session. When no more streams are processed, the
connection is released and can be reused.
- "aggressive" : this mode may be useful in webservices environments where
all servers are not necessarily known and where it would be
appreciable to deliver most first requests over existing
connections. In this case, first requests are only delivered
over existing connections that have been reused at least once,
proving that the server correctly supports connection reuse.
It should only be used when it's sure that the client can
retry a failed request once in a while and where the benefit
of aggressive connection reuse significantly outweighs the
downsides of rare connection failures.
- "always" : this mode is only recommended when the path to the server is
known for never breaking existing connections quickly after
releasing them. It allows the first request of a session to be
sent to an existing connection. This can provide a significant
performance increase over the "safe" strategy when the backend
is a cache farm, since such components tend to show a
consistent behavior and will benefit from the connection
sharing. It is recommended that the "http-keep-alive" timeout
remains low in this mode so that no dead connections remain
usable. In most cases, this will lead to the same performance
gains as "aggressive" but with more risks. It should only be
used when it improves the situation over "aggressive".
When http connection sharing is enabled, a great care is taken to respect the
connection properties and compatibility. Indeed, some properties are specific
and it is not possibly to reuse it blindly. Those are the SSL SNI, source
and destination address and proxy protocol block. A connection is reused only
if it shares the same set of properties with the request.
Also note that connections with certain bogus authentication schemes (relying
on the connection) like NTLM are marked private and never shared.
A connection pool is involved and configurable with "pool-max-conn".
Note: connection reuse improves the accuracy of the "server maxconn" setting,
because almost no new connection will be established while idle connections
remain available. This is particularly true with the "always" strategy.
See also : "
option http-keep-alive", "server maxconn"
Add the server name to a request. Use the header string given by <header>
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<header> The header string to use to send the server name
The "http-send-name-header" statement causes the header field named <header>
to be set to the name of the target server at the moment the request is about
to be sent on the wire. Any existing occurrences of this header are removed.
Upon retries and redispatches, the header field is updated to always reflect
the server being attempted to connect to. Given that this header is modified
very late in the connection setup, it may have unexpected effects on already
modified headers. For example using it with transport-level header such as
connection, content-length, transfer-encoding and so on will likely result in
invalid requests being sent to the server. Additionally it has been reported
that this directive is currently being used as a way to overwrite the Host
header field in outgoing requests; while this trick has been known to work
as a side effect of the feature for some time, it is not officially supported
and might possibly not work anymore in a future version depending on the
technical difficulties this feature induces. A long-term solution instead
consists in fixing the application which required this trick so that it binds
to the correct host name.
See also : "
server"
id <value>
Set a persistent ID to a proxy.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
Set a persistent ID for the proxy. This ID must be unique and positive.
An unused ID will automatically be assigned if unset. The first assigned
value will be 1. This ID is currently only returned in statistics.
ignore-persist { if | unless } <condition>
Declare a condition to ignore persistence
May be used in sections :
defaults |
frontend |
listen |
backend |
By default, when cookie persistence is enabled, every requests containing
the cookie are unconditionally persistent (assuming the target server is up
and running).
The "ignore-persist" statement allows one to declare various ACL-based
conditions which, when met, will cause a request to ignore persistence.
This is sometimes useful to load balance requests for static files, which
often don't require persistence. This can also be used to fully disable
persistence for a specific User-Agent (for example, some web crawler bots).
The persistence is ignored when an "if" condition is met, or unless an
"unless" condition is met.
Example:
acl url_static path_beg /static /images /img /css
acl url_static path_end .gif .png .jpg .css .js
ignore-persist if url_static
See also : "
force-persist", "
cookie", and
section 7 about ACL usage.
load-server-state-from-file { global | local | none }
Allow seamless reload of HAProxy
May be used in sections :
defaults |
frontend |
listen |
backend |
This directive points HAProxy to a file where server state from previous
running process has been saved. That way, when starting up, before handling
traffic, the new process can apply old states to servers exactly has if no
reload occurred. The purpose of the "load-server-state-from-file" directive is
to tell HAProxy which file to use. For now, only 2 arguments to either prevent
loading state or load states from a file containing all backends and servers.
The state file can be generated by running the command "show servers state"
over the stats socket and redirect output.
The format of the file is versioned and is very specific. To understand it,
please read the documentation of the "show servers state" command (chapter
9.3 of Management Guide).
Arguments:global load the content of the file pointed by the global directive
named "server-state-file".
local load the content of the file pointed by the directive
"server-state-file-name" if set. If not set, then the backend
name is used as a file name.
none don't load any stat for this backend
Notes:
- server's IP address is preserved across reloads by default, but the
order can be changed thanks to the server's "init-addr" setting. This
means that an IP address change performed on the CLI at run time will
be preserved, and that any change to the local resolver (e.g. /etc/hosts)
will possibly not have any effect if the state file is in use.
- server's weight is applied from previous running process unless it has
has changed between previous and new configuration files.
Example:
Minimal configuration
global
stats socket /tmp/socket
server-state-file /tmp/server_state
defaults
load-server-state-from-file global
backend bk
server s1 127.0.0.1:22 check weight 11
server s2 127.0.0.1:22 check weight 12
Then one can run :
socat /tmp/socket - <<< "show servers state" > /tmp/server_state
Content of the file /tmp/server_state would be like this:
1
# <field names skipped for the doc example>
1 bk 1 s1 127.0.0.1 2 0 11 11 4 6 3 4 6 0 0
1 bk 2 s2 127.0.0.1 2 0 12 12 4 6 3 4 6 0 0
Example:
Minimal configuration
global
stats socket /tmp/socket
server-state-base /etc/haproxy/states
defaults
load-server-state-from-file local
backend bk
server s1 127.0.0.1:22 check weight 11
server s2 127.0.0.1:22 check weight 12
Then one can run :
socat /tmp/socket - <<< "show servers state bk" > /etc/haproxy/states/bk
Content of the file /etc/haproxy/states/bk would be like this:
1
# <field names skipped for the doc example>
1 bk 1 s1 127.0.0.1 2 0 11 11 4 6 3 4 6 0 0
1 bk 2 s2 127.0.0.1 2 0 12 12 4 6 3 4 6 0 0
See also: "
server-state-file", "
server-state-file-name", and "show servers state"
log global
log <address> [len <length>] [format <format>] [sample <ranges>:<sample_size>] <facility> [<level> [<minlevel>]]
no log
Enable per-instance logging of events and traffic.
May be used in sections :
defaults |
frontend |
listen |
backend |
Prefix :
no should be used when the logger list must be flushed. For example,
if you don't want to inherit from the default logger list. This
prefix does not allow arguments.
Arguments :global should be used when the instance's logging parameters are the
same as the global ones. This is the most common usage. "global"
replaces <address>, <facility> and <level> with those of the log
entries found in the "global" section. Only one "log global"
statement may be used per instance, and this form takes no other
parameter.
<address> indicates where to send the logs. It takes the same format as
for the "global" section's logs, and can be one of :
- An IPv4 address optionally followed by a colon (':') and a UDP
port. If no port is specified, 514 is used by default (the
standard syslog port).
- An IPv6 address followed by a colon (':') and optionally a UDP
port. If no port is specified, 514 is used by default (the
standard syslog port).
- A filesystem path to a UNIX domain socket, keeping in mind
considerations for chroot (be sure the path is accessible
inside the chroot) and uid/gid (be sure the path is
appropriately writable).
- A file descriptor number in the form "fd@<number>", which may
point to a pipe, terminal, or socket. In this case unbuffered
logs are used and one writev() call per log is performed. This
is a bit expensive but acceptable for most workloads. Messages
sent this way will not be truncated but may be dropped, in
which case the DroppedLogs counter will be incremented. The
writev() call is atomic even on pipes for messages up to
PIPE_BUF size, which POSIX recommends to be at least 512 and
which is 4096 bytes on most modern operating systems. Any
larger message may be interleaved with messages from other
processes. Exceptionally for debugging purposes the file
descriptor may also be directed to a file, but doing so will
significantly slow HAProxy down as non-blocking calls will be
ignored. Also there will be no way to purge nor rotate this
file without restarting the process. Note that the configured
syslog format is preserved, so the output is suitable for use
with a TCP syslog server. See also the "short" and "raw"
formats below.
- "stdout" / "stderr", which are respectively aliases for "fd@1"
and "fd@2", see above.
- A ring buffer in the form "ring@<name>", which will correspond
to an in-memory ring buffer accessible over the CLI using the
"show events" command, which will also list existing rings and
their sizes. Such buffers are lost on reload or restart but
when used as a complement this can help troubleshooting by
having the logs instantly available.
- An explicit stream address prefix such as "tcp@","tcp6@",
"tcp4@" or "uxst@" will allocate an implicit ring buffer with
a stream forward server targeting the given address.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment variables.
<length> is an optional maximum line length. Log lines larger than this
value will be truncated before being sent. The reason is that
syslog servers act differently on log line length. All servers
support the default value of 1024, but some servers simply drop
larger lines while others do log them. If a server supports long
lines, it may make sense to set this value here in order to avoid
truncating long lines. Similarly, if a server drops long lines,
it is preferable to truncate them before sending them. Accepted
values are 80 to 65535 inclusive. The default value of 1024 is
generally fine for all standard usages. Some specific cases of
long captures or JSON-formatted logs may require larger values.
<ranges> A list of comma-separated ranges to identify the logs to sample.
This is used to balance the load of the logs to send to the log
server. The limits of the ranges cannot be null. They are numbered
from 1. The size or period (in number of logs) of the sample must
be set with <sample_size> parameter.
<sample_size>
The size of the sample in number of logs to consider when balancing
their logging loads. It is used to balance the load of the logs to
send to the syslog server. This size must be greater or equal to the
maximum of the high limits of the ranges.
(see also <ranges> parameter).
<format> is the log format used when generating syslog messages. It may be
one of the following :
local Analog to rfc3164 syslog message format except that hostname
field is stripped. This is the default.
Note: option "log-send-hostname" switches the default to
rfc3164.
rfc3164 The RFC3164 syslog message format.
(https://tools.ietf.org/html/rfc3164)
rfc5424 The RFC5424 syslog message format.
(https://tools.ietf.org/html/rfc5424)
priority A message containing only a level plus syslog facility between
angle brackets such as '<63>', followed by the text. The PID,
date, time, process name and system name are omitted. This is
designed to be used with a local log server.
short A message containing only a level between angle brackets such as
'<3>', followed by the text. The PID, date, time, process name
and system name are omitted. This is designed to be used with a
local log server. This format is compatible with what the
systemd logger consumes.
timed A message containing only a level between angle brackets such as
'<3>', followed by ISO date and by the text. The PID, process
name and system name are omitted. This is designed to be
used with a local log server.
iso A message containing only the ISO date, followed by the text.
The PID, process name and system name are omitted. This is
designed to be used with a local log server.
raw A message containing only the text. The level, PID, date, time,
process name and system name are omitted. This is designed to
be used in containers or during development, where the severity
only depends on the file descriptor used (stdout/stderr).
<facility> must be one of the 24 standard syslog facilities :
kern user mail daemon auth syslog lpr news
uucp cron auth2 ftp ntp audit alert cron2
local0 local1 local2 local3 local4 local5 local6 local7
Note that the facility is ignored for the "short" and "raw"
formats, but still required as a positional field. It is
recommended to use "daemon" in this case to make it clear that
it's only supposed to be used locally.
<level> is optional and can be specified to filter outgoing messages. By
default, all messages are sent. If a level is specified, only
messages with a severity at least as important as this level
will be sent. An optional minimum level can be specified. If it
is set, logs emitted with a more severe level than this one will
be capped to this level. This is used to avoid sending "emerg"
messages on all terminals on some default syslog configurations.
Eight levels are known :
emerg alert crit err warning notice info debug
It is important to keep in mind that it is the frontend which decides what to
log from a connection, and that in case of content switching, the log entries
from the backend will be ignored. Connections are logged at level "info".
However, backend log declaration define how and where servers status changes
will be logged. Level "notice" will be used to indicate a server going up,
"warning" will be used for termination signals and definitive service
termination, and "alert" will be used for when a server goes down.
Note : According to RFC3164, messages are truncated to 1024 bytes before
being emitted.
Example :
log global
log stdout format short daemon
log stdout format raw daemon
log stderr format raw daemon notice
log 127.0.0.1:514 local0 notice
log [email protected]:514 local0 notice notice
log "${LOCAL_SYSLOG}:514" local0 notice
log-format <string>
Specifies the log format string to use for traffic logs
May be used in sections :
defaults |
frontend |
listen |
backend |
This directive specifies the log format string that will be used for all logs
resulting from traffic passing through the frontend using this line. If the
directive is used in a defaults section, all subsequent frontends will use
the same log format. Please see section 8.2.4 which covers the log format
string in depth.
"log-format" directive overrides previous "option tcplog", "log-format" and
"option httplog" directives.
log-format-sd <string>
Specifies the RFC5424 structured-data log format string
May be used in sections :
defaults |
frontend |
listen |
backend |
This directive specifies the RFC5424 structured-data log format string that
will be used for all logs resulting from traffic passing through the frontend
using this line. If the directive is used in a defaults section, all
subsequent frontends will use the same log format. Please see section 8.2.4
which covers the log format string in depth.
See https://tools.ietf.org/html/rfc5424#section-6.3 for more information
about the RFC5424 structured-data part.
Note : This log format string will be used only for loggers that have set
log format to "rfc5424".
Example :
log-format-sd [exampleSDID@1234\ bytes=\"%B\"\ status=\"%ST\"]
log-tag <string>
Specifies the log tag to use for all outgoing logs
May be used in sections :
defaults |
frontend |
listen |
backend |
Sets the tag field in the syslog header to this string. It defaults to the
log-tag set in the global section, otherwise the program name as launched
from the command line, which usually is "HAProxy". Sometimes it can be useful
to differentiate between multiple processes running on the same host, or to
differentiate customer instances running in the same process. In the backend,
logs about servers up/down will use this tag. As a hint, it can be convenient
to set a log-tag related to a hosted customer in a defaults section then put
all the frontends and backends for that customer, then start another customer
in a new defaults section. See also the global "log-tag" directive.
max-keep-alive-queue <value>
Set the maximum server queue size for maintaining keep-alive connections
May be used in sections :
defaults |
frontend |
listen |
backend |
HTTP keep-alive tries to reuse the same server connection whenever possible,
but sometimes it can be counter-productive, for example if a server has a lot
of connections while other ones are idle. This is especially true for static
servers.
The purpose of this setting is to set a threshold on the number of queued
connections at which HAProxy stops trying to reuse the same server and prefers
to find another one. The default value, -1, means there is no limit. A value
of zero means that keep-alive requests will never be queued. For very close
servers which can be reached with a low latency and which are not sensible to
breaking keep-alive, a low value is recommended (e.g. local static server can
use a value of 10 or less). For remote servers suffering from a high latency,
higher values might be needed to cover for the latency and/or the cost of
picking a different server.
Note that this has no impact on responses which are maintained to the same
server consecutively to a 401 response. They will still go to the same server
even if they have to be queued.
See also : "
option http-server-close", "
option prefer-last-server", server "
maxconn" and cookie persistence.
max-session-srv-conns <nb>
Set the maximum number of outgoing connections we can keep idling for a given
client session. The default is 5 (it precisely equals MAX_SRV_LIST which is
defined at build time).
maxconn <conns>
Fix the maximum number of concurrent connections on a frontend
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<conns> is the maximum number of concurrent connections the frontend will
accept to serve. Excess connections will be queued by the system
in the socket's listen queue and will be served once a connection
closes.
If the system supports it, it can be useful on big sites to raise this limit
very high so that HAProxy manages connection queues, instead of leaving the
clients with unanswered connection attempts. This value should not exceed the
global maxconn. Also, keep in mind that a connection contains two buffers
of tune.bufsize (16kB by default) each, as well as some other data resulting
in about 33 kB of RAM being consumed per established connection. That means
that a medium system equipped with 1GB of RAM can withstand around
20000-25000 concurrent connections if properly tuned.
Also, when <conns> is set to large values, it is possible that the servers
are not sized to accept such loads, and for this reason it is generally wise
to assign them some reasonable connection limits.
When this value is set to zero, which is the default, the global "maxconn"
value is used.
See also : "
server", global section's "
maxconn", "
fullconn"
mode { tcp|http }
Set the running mode or protocol of the instance
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :tcp The instance will work in pure TCP mode. A full-duplex connection
will be established between clients and servers, and no layer 7
examination will be performed. This is the default mode. It
should be used for SSL, SSH, SMTP, ...
http The instance will work in HTTP mode. The client request will be
analyzed in depth before connecting to any server. Any request
which is not RFC-compliant will be rejected. Layer 7 filtering,
processing and switching will be possible. This is the mode which
brings HAProxy most of its value.
When doing content switching, it is mandatory that the frontend and the
backend are in the same mode (generally HTTP), otherwise the configuration
will be refused.
Example :
defaults http_instances
mode http
monitor fail { if | unless } <condition>
Add a condition to report a failure to a monitor HTTP request.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :if <cond> the monitor request will fail if the condition is satisfied,
and will succeed otherwise. The condition should describe a
combined test which must induce a failure if all conditions
are met, for instance a low number of servers both in a
backend and its backup.
unless <cond> the monitor request will succeed only if the condition is
satisfied, and will fail otherwise. Such a condition may be
based on a test on the presence of a minimum number of active
servers in a list of backends.
This statement adds a condition which can force the response to a monitor
request to report a failure. By default, when an external component queries
the URI dedicated to monitoring, a 200 response is returned. When one of the
conditions above is met, HAProxy will return 503 instead of 200. This is
very useful to report a site failure to an external component which may base
routing advertisements between multiple sites on the availability reported by
HAProxy. In this case, one would rely on an ACL involving the "nbsrv"
criterion. Note that "monitor fail" only works in HTTP mode. Both status
messages may be tweaked using "errorfile" or "errorloc" if needed.
Example:
frontend www
mode http
acl site_dead nbsrv(dynamic) lt 2
acl site_dead nbsrv(static) lt 2
monitor-uri /site_alive
monitor fail if site_dead
See also : "
monitor-uri", "
errorfile", "
errorloc"
monitor-uri <uri>
Intercept a URI used by external components' monitor requests
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<uri> is the exact URI which we want to intercept to return HAProxy's
health status instead of forwarding the request.
When an HTTP request referencing <uri> will be received on a frontend,
HAProxy will not forward it nor log it, but instead will return either
"HTTP/1.0 200 OK" or "HTTP/1.0 503 Service unavailable", depending on failure
conditions defined with "monitor fail". This is normally enough for any
front-end HTTP probe to detect that the service is UP and running without
forwarding the request to a backend server. Note that the HTTP method, the
version and all headers are ignored, but the request must at least be valid
at the HTTP level. This keyword may only be used with an HTTP-mode frontend.
Monitor requests are processed very early, just after the request is parsed
and even before any "http-request". The only rulesets applied before are the
tcp-request ones. They cannot be logged either, and it is the intended
purpose. They are only used to report HAProxy's health to an upper component,
nothing more. However, it is possible to add any number of conditions using
"monitor fail" and ACLs so that the result can be adjusted to whatever check
can be imagined (most often the number of available servers in a backend).
Note: if <uri> starts by a slash ('/'), the matching is performed against the
request's path instead of the request's uri. It is a workaround to let
the HTTP/2 requests match the monitor-uri. Indeed, in HTTP/2, clients
are encouraged to send absolute URIs only.
Example :
frontend www
mode http
monitor-uri /haproxy_test
See also : "
monitor fail"
option abortonclose
no option abortonclose
Enable or disable early dropping of aborted requests pending in queues.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
In presence of very high loads, the servers will take some time to respond.
The per-instance connection queue will inflate, and the response time will
increase respective to the size of the queue times the average per-session
response time. When clients will wait for more than a few seconds, they will
often hit the "STOP" button on their browser, leaving a useless request in
the queue, and slowing down other users, and the servers as well, because the
request will eventually be served, then aborted at the first error
encountered while delivering the response.
As there is no way to distinguish between a full STOP and a simple output
close on the client side, HTTP agents should be conservative and consider
that the client might only have closed its output channel while waiting for
the response. However, this introduces risks of congestion when lots of users
do the same, and is completely useless nowadays because probably no client at
all will close the session while waiting for the response. Some HTTP agents
support this behavior (Squid, Apache, HAProxy), and others do not (TUX, most
hardware-based load balancers). So the probability for a closed input channel
to represent a user hitting the "STOP" button is close to 100%, and the risk
of being the single component to break rare but valid traffic is extremely
low, which adds to the temptation to be able to abort a session early while
still not served and not pollute the servers.
In HAProxy, the user can choose the desired behavior using the option
"abortonclose". By default (without the option) the behavior is HTTP
compliant and aborted requests will be served. But when the option is
specified, a session with an incoming channel closed will be aborted while
it is still possible, either pending in the queue for a connection slot, or
during the connection establishment if the server has not yet acknowledged
the connection request. This considerably reduces the queue size and the load
on saturated servers when users are tempted to click on STOP, which in turn
reduces the response time for other users.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
timeout queue" and server's "
maxconn" and "
maxqueue" parameters
option accept-invalid-http-request
no option accept-invalid-http-request
Enable or disable relaxing of HTTP request parsing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, HAProxy complies with RFC7230 in terms of message parsing. This
means that invalid characters in header names are not permitted and cause an
error to be returned to the client. This is the desired behavior as such
forbidden characters are essentially used to build attacks exploiting server
weaknesses, and bypass security filtering. Sometimes, a buggy browser or
server will emit invalid header names for whatever reason (configuration,
implementation) and the issue will not be immediately fixed. In such a case,
it is possible to relax HAProxy's header name parser to accept any character
even if that does not make sense, by specifying this option. Similarly, the
list of characters allowed to appear in a URI is well defined by RFC3986, and
chars 0-31, 32 (space), 34 ('"'), 60 ('<'), 62 ('>'), 92 ('\'), 94 ('^'), 96
('`'), 123 ('{'), 124 ('|'), 125 ('}'), 127 (delete) and anything above are
not allowed at all. HAProxy always blocks a number of them (0..32, 127). The
remaining ones are blocked by default unless this option is enabled. This
option also relaxes the test on the HTTP version, it allows HTTP/0.9 requests
to pass through (no version specified) and multiple digits for both the major
and the minor version.
This option should never be enabled by default as it hides application bugs
and open security breaches. It should only be deployed after a problem has
been confirmed.
When this option is enabled, erroneous header names will still be accepted in
requests, but the complete request will be captured in order to permit later
analysis using the "show errors" request on the UNIX stats socket. Similarly,
requests containing invalid chars in the URI part will be logged. Doing this
also helps confirming that the issue has been solved.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option accept-invalid-http-response" and "show errors" on the stats socket.
option accept-invalid-http-response
no option accept-invalid-http-response
Enable or disable relaxing of HTTP response parsing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, HAProxy complies with RFC7230 in terms of message parsing. This
means that invalid characters in header names are not permitted and cause an
error to be returned to the client. This is the desired behavior as such
forbidden characters are essentially used to build attacks exploiting server
weaknesses, and bypass security filtering. Sometimes, a buggy browser or
server will emit invalid header names for whatever reason (configuration,
implementation) and the issue will not be immediately fixed. In such a case,
it is possible to relax HAProxy's header name parser to accept any character
even if that does not make sense, by specifying this option. This option also
relaxes the test on the HTTP version format, it allows multiple digits for
both the major and the minor version.
This option should never be enabled by default as it hides application bugs
and open security breaches. It should only be deployed after a problem has
been confirmed.
When this option is enabled, erroneous header names will still be accepted in
responses, but the complete response will be captured in order to permit
later analysis using the "show errors" request on the UNIX stats socket.
Doing this also helps confirming that the issue has been solved.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option accept-invalid-http-request" and "show errors" on the stats socket.
option allbackups
no option allbackups
Use either all backup servers at a time or only the first one
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, the first operational backup server gets all traffic when normal
servers are all down. Sometimes, it may be preferred to use multiple backups
at once, because one will not be enough. When "option allbackups" is enabled,
the load balancing will be performed among all backup servers when all normal
ones are unavailable. The same load balancing algorithm will be used and the
servers' weights will be respected. Thus, there will not be any priority
order between the backup servers anymore.
This option is mostly used with static server farms dedicated to return a
"sorry" page when an application is completely offline.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
option checkcache
no option checkcache
Analyze all server responses and block responses with cacheable cookies
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
Some high-level frameworks set application cookies everywhere and do not
always let enough control to the developer to manage how the responses should
be cached. When a session cookie is returned on a cacheable object, there is a
high risk of session crossing or stealing between users traversing the same
caches. In some situations, it is better to block the response than to let
some sensitive session information go in the wild.
The option "checkcache" enables deep inspection of all server responses for
strict compliance with HTTP specification in terms of cacheability. It
carefully checks "Cache-control", "Pragma" and "Set-cookie" headers in server
response to check if there's a risk of caching a cookie on a client-side
proxy. When this option is enabled, the only responses which can be delivered
to the client are :
- all those without "Set-Cookie" header;
- all those with a return code other than 200, 203, 204, 206, 300, 301,
404, 405, 410, 414, 501, provided that the server has not set a
"Cache-control: public" header field;
- all those that result from a request using a method other than GET, HEAD,
OPTIONS, TRACE, provided that the server has not set a 'Cache-Control:
public' header field;
- those with a 'Pragma: no-cache' header
- those with a 'Cache-control: private' header
- those with a 'Cache-control: no-store' header
- those with a 'Cache-control: max-age=0' header
- those with a 'Cache-control: s-maxage=0' header
- those with a 'Cache-control: no-cache' header
- those with a 'Cache-control: no-cache="set-cookie"' header
- those with a 'Cache-control: no-cache="set-cookie,' header
(allowing other fields after set-cookie)
If a response doesn't respect these requirements, then it will be blocked
just as if it was from an "http-response deny" rule, with an "HTTP 502 bad
gateway". The session state shows "PH--" meaning that the proxy blocked the
response during headers processing. Additionally, an alert will be sent in
the logs so that admins are informed that there's something to be fixed.
Due to the high impact on the application, the application should be tested
in depth with the option enabled before going to production. It is also a
good practice to always activate it during tests, even if it is not used in
production, as it will report potentially dangerous application behaviors.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
option clitcpka
no option clitcpka
Enable or disable the sending of TCP keepalive packets on the client side
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When there is a firewall or any session-aware component between a client and
a server, and when the protocol involves very long sessions with long idle
periods (e.g. remote desktops), there is a risk that one of the intermediate
components decides to expire a session which has remained idle for too long.
Enabling socket-level TCP keep-alives makes the system regularly send packets
to the other end of the connection, leaving it active. The delay between
keep-alive probes is controlled by the system only and depends both on the
operating system and its tuning parameters.
It is important to understand that keep-alive packets are neither emitted nor
received at the application level. It is only the network stacks which sees
them. For this reason, even if one side of the proxy already uses keep-alives
to maintain its connection alive, those keep-alive packets will not be
forwarded to the other side of the proxy.
Please note that this has nothing to do with HTTP keep-alive.
Using option "clitcpka" enables the emission of TCP keep-alive probes on the
client side of a connection, which should help when session expirations are
noticed between HAProxy and a client.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option srvtcpka", "
option tcpka"
option contstats
Enable continuous traffic statistics updates
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, counters used for statistics calculation are incremented
only when a session finishes. It works quite well when serving small
objects, but with big ones (for example large images or archives) or
with A/V streaming, a graph generated from HAProxy counters looks like
a hedgehog. With this option enabled counters get incremented frequently
along the session, typically every 5 seconds, which is often enough to
produce clean graphs. Recounting touches a hotpath directly so it is not
not enabled by default, as it can cause a lot of wakeups for very large
session counts and cause a small performance drop.
option disable-h2-upgrade
no option disable-h2-upgrade
Enable or disable the implicit HTTP/2 upgrade from an HTTP/1.x client
connection.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, HAProxy is able to implicitly upgrade an HTTP/1.x client
connection to an HTTP/2 connection if the first request it receives from a
given HTTP connection matches the HTTP/2 connection preface (i.e. the string
"PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"). This way, it is possible to support
HTTP/1.x and HTTP/2 clients on a non-SSL connections. This option must be
used to disable the implicit upgrade. Note this implicit upgrade is only
supported for HTTP proxies, thus this option too. Note also it is possible to
force the HTTP/2 on clear connections by specifying "proto h2" on the bind
line. Finally, this option is applied on all bind lines. To disable implicit
HTTP/2 upgrades for a specific bind line, it is possible to use "proto h1".
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
option dontlog-normal
no option dontlog-normal
Enable or disable logging of normal, successful connections
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
There are large sites dealing with several thousand connections per second
and for which logging is a major pain. Some of them are even forced to turn
logs off and cannot debug production issues. Setting this option ensures that
normal connections, those which experience no error, no timeout, no retry nor
redispatch, will not be logged. This leaves disk space for anomalies. In HTTP
mode, the response status code is checked and return codes 5xx will still be
logged.
It is strongly discouraged to use this option as most of the time, the key to
complex issues is in the normal logs which will not be logged here. If you
need to separate logs, see the "log-separate-errors" option instead.
See also : "
log", "
dontlognull", "
log-separate-errors" and
section 8 about logging.
option dontlognull
no option dontlognull
Enable or disable logging of null connections
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
In certain environments, there are components which will regularly connect to
various systems to ensure that they are still alive. It can be the case from
another load balancer as well as from monitoring systems. By default, even a
simple port probe or scan will produce a log. If those connections pollute
the logs too much, it is possible to enable option "dontlognull" to indicate
that a connection on which no data has been transferred will not be logged,
which typically corresponds to those probes. Note that errors will still be
returned to the client and accounted for in the stats. If this is not what is
desired, option http-ignore-probes can be used instead.
It is generally recommended not to use this option in uncontrolled
environments (e.g. internet), otherwise scans and other malicious activities
would not be logged.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
log", "
http-ignore-probes", "
monitor-uri", and
section 8 about logging.
option forwardfor [ except <network> ] [ header <name> ] [ if-none ]
Enable insertion of the X-Forwarded-For header to requests sent to servers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<network> is an optional argument used to disable this option for sources
matching <network>
<name> an optional argument to specify a different "X-Forwarded-For"
header name.
Since HAProxy works in reverse-proxy mode, the servers see its IP address as
their client address. This is sometimes annoying when the client's IP address
is expected in server logs. To solve this problem, the well-known HTTP header
"X-Forwarded-For" may be added by HAProxy to all requests sent to the server.
This header contains a value representing the client's IP address. Since this
header is always appended at the end of the existing header list, the server
must be configured to always use the last occurrence of this header only. See
the server's manual to find how to enable use of this standard header. Note
that only the last occurrence of the header must be used, since it is really
possible that the client has already brought one.
The keyword "header" may be used to supply a different header name to replace
the default "X-Forwarded-For". This can be useful where you might already
have a "X-Forwarded-For" header from a different application (e.g. stunnel),
and you need preserve it. Also if your backend server doesn't use the
"X-Forwarded-For" header and requires different one (e.g. Zeus Web Servers
require "X-Cluster-Client-IP").
Sometimes, a same HAProxy instance may be shared between a direct client
access and a reverse-proxy access (for instance when an SSL reverse-proxy is
used to decrypt HTTPS traffic). It is possible to disable the addition of the
header for a known source address or network by adding the "except" keyword
followed by the network address. In this case, any source IP matching the
network will not cause an addition of this header. Most common uses are with
private networks or 127.0.0.1. IPv4 and IPv6 are both supported.
Alternatively, the keyword "if-none" states that the header will only be
added if it is not present. This should only be used in perfectly trusted
environment, as this might cause a security issue if headers reaching HAProxy
are under the control of the end-user.
This option may be specified either in the frontend or in the backend. If at
least one of them uses it, the header will be added. Note that the backend's
setting of the header subargument takes precedence over the frontend's if
both are defined. In the case of the "if-none" argument, if at least one of
the frontend or the backend does not specify it, it wants the addition to be
mandatory, so it wins.
Example :
frontend www
mode http
option forwardfor except 127.0.0.1
backend www
mode http
option forwardfor header X-Client
See also : "
option httpclose", "
option http-server-close", "
option http-keep-alive"
option h1-case-adjust-bogus-client
no option h1-case-adjust-bogus-client
Enable or disable the case adjustment of HTTP/1 headers sent to bogus clients
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
There is no standard case for header names because, as stated in RFC7230,
they are case-insensitive. So applications must handle them in a case-
insensitive manner. But some bogus applications violate the standards and
erroneously rely on the cases most commonly used by browsers. This problem
becomes critical with HTTP/2 because all header names must be exchanged in
lower case, and HAProxy follows the same convention. All header names are
sent in lower case to clients and servers, regardless of the HTTP version.
When HAProxy receives an HTTP/1 response, its header names are converted to
lower case and manipulated and sent this way to the clients. If a client is
known to violate the HTTP standards and to fail to process a response coming
from HAProxy, it is possible to transform the lower case header names to a
different format when the response is formatted and sent to the client, by
enabling this option and specifying the list of headers to be reformatted
using the global directives "h1-case-adjust" or "h1-case-adjust-file". This
must only be a temporary workaround for the time it takes the client to be
fixed, because clients which require such workarounds might be vulnerable to
content smuggling attacks and must absolutely be fixed.
Please note that this option will not affect standards-compliant clients.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also: "
option h1-case-adjust-bogus-server", "
h1-case-adjust", "
h1-case-adjust-file".
option h1-case-adjust-bogus-server
no option h1-case-adjust-bogus-server
Enable or disable the case adjustment of HTTP/1 headers sent to bogus servers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
There is no standard case for header names because, as stated in RFC7230,
they are case-insensitive. So applications must handle them in a case-
insensitive manner. But some bogus applications violate the standards and
erroneously rely on the cases most commonly used by browsers. This problem
becomes critical with HTTP/2 because all header names must be exchanged in
lower case, and HAProxy follows the same convention. All header names are
sent in lower case to clients and servers, regardless of the HTTP version.
When HAProxy receives an HTTP/1 request, its header names are converted to
lower case and manipulated and sent this way to the servers. If a server is
known to violate the HTTP standards and to fail to process a request coming
from HAProxy, it is possible to transform the lower case header names to a
different format when the request is formatted and sent to the server, by
enabling this option and specifying the list of headers to be reformatted
using the global directives "h1-case-adjust" or "h1-case-adjust-file". This
must only be a temporary workaround for the time it takes the server to be
fixed, because servers which require such workarounds might be vulnerable to
content smuggling attacks and must absolutely be fixed.
Please note that this option will not affect standards-compliant servers.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also: "
option h1-case-adjust-bogus-client", "
h1-case-adjust", "
h1-case-adjust-file".
option http-buffer-request
no option http-buffer-request
Enable or disable waiting for whole HTTP request body before proceeding
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
It is sometimes desirable to wait for the body of an HTTP request before
taking a decision. This is what is being done by "balance url_param" for
example. The first use case is to buffer requests from slow clients before
connecting to the server. Another use case consists in taking the routing
decision based on the request body's contents. This option placed in a
frontend or backend forces the HTTP processing to wait until either the whole
body is received or the request buffer is full. It can have undesired side
effects with some applications abusing HTTP by expecting unbuffered
transmissions between the frontend and the backend, so this should definitely
not be used by default.
See also : "
option http-no-delay", "
timeout http-request", "
http-request wait-for-body"
option http-ignore-probes
no option http-ignore-probes
Enable or disable logging of null connections and request timeouts
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
Recently some browsers started to implement a "pre-connect" feature
consisting in speculatively connecting to some recently visited web sites
just in case the user would like to visit them. This results in many
connections being established to web sites, which end up in 408 Request
Timeout if the timeout strikes first, or 400 Bad Request when the browser
decides to close them first. These ones pollute the log and feed the error
counters. There was already "option dontlognull" but it's insufficient in
this case. Instead, this option does the following things :
- prevent any 400/408 message from being sent to the client if nothing
was received over a connection before it was closed;
- prevent any log from being emitted in this situation;
- prevent any error counter from being incremented
That way the empty connection is silently ignored. Note that it is better
not to use this unless it is clear that it is needed, because it will hide
real problems. The most common reason for not receiving a request and seeing
a 408 is due to an MTU inconsistency between the client and an intermediary
element such as a VPN, which blocks too large packets. These issues are
generally seen with POST requests as well as GET with large cookies. The logs
are often the only way to detect them.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
log", "
dontlognull", "
errorfile", and
section 8 about logging.
option http-keep-alive
no option http-keep-alive
Enable or disable HTTP keep-alive from client to server
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and
the start of a new request. This mode may be changed by several options such
as "option http-server-close" or "option httpclose". This option allows to
set back the keep-alive mode, which can be useful when another mode was used
in a defaults section.
Setting "option http-keep-alive" enables HTTP keep-alive mode on the client-
and server- sides. This provides the lowest latency on the client side (slow
network) and the fastest session reuse on the server side at the expense
of maintaining idle connections to the servers. In general, it is possible
with this option to achieve approximately twice the request rate that the
"http-server-close" option achieves on small objects. There are mainly two
situations where this option may be useful :
- when the server is non-HTTP compliant and authenticates the connection
instead of requests (e.g. NTLM authentication)
- when the cost of establishing the connection to the server is significant
compared to the cost of retrieving the associated object from the server.
This last case can happen when the server is a fast static server of cache.
In this case, the server will need to be properly tuned to support high enough
connection counts because connections will last until the client sends another
request.
If the client request has to go to another backend or another server due to
content switching or the load balancing algorithm, the idle connection will
immediately be closed and a new one re-opened. Option "prefer-last-server" is
available to try optimize server selection so that if the server currently
attached to an idle connection is usable, it will be used.
At the moment, logs will not indicate whether requests came from the same
session or not. The accept date reported in the logs corresponds to the end
of the previous request, and the request time corresponds to the time spent
waiting for a new request. The keep-alive request time is still bound to the
timeout defined by "timeout http-keep-alive" or "timeout http-request" if
not set.
This option disables and replaces any previous "option httpclose" or "option
http-server-close". When backend and frontend options differ, all of these 4
options have precedence over "option http-keep-alive".
See also : "
option httpclose",, "
option http-server-close", "
option prefer-last-server", "
option http-pretend-keepalive", and "1.1. The HTTP transaction model".
option http-no-delay
no option http-no-delay
Instruct the system to favor low interactive delays over performance in HTTP
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
In HTTP, each payload is unidirectional and has no notion of interactivity.
Any agent is expected to queue data somewhat for a reasonably low delay.
There are some very rare server-to-server applications that abuse the HTTP
protocol and expect the payload phase to be highly interactive, with many
interleaved data chunks in both directions within a single request. This is
absolutely not supported by the HTTP specification and will not work across
most proxies or servers. When such applications attempt to do this through
HAProxy, it works but they will experience high delays due to the network
optimizations which favor performance by instructing the system to wait for
enough data to be available in order to only send full packets. Typical
delays are around 200 ms per round trip. Note that this only happens with
abnormal uses. Normal uses such as CONNECT requests nor WebSockets are not
affected.
When "option http-no-delay" is present in either the frontend or the backend
used by a connection, all such optimizations will be disabled in order to
make the exchanges as fast as possible. Of course this offers no guarantee on
the functionality, as it may break at any other place. But if it works via
HAProxy, it will work as fast as possible. This option should never be used
by default, and should never be used at all unless such a buggy application
is discovered. The impact of using this option is an increase of bandwidth
usage and CPU usage, which may significantly lower performance in high
latency environments.
See also : "
option http-buffer-request"
option http-pretend-keepalive
no option http-pretend-keepalive
Define whether HAProxy will announce keepalive to the server or not
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When running with "option http-server-close" or "option httpclose", HAProxy
adds a "Connection: close" header to the request forwarded to the server.
Unfortunately, when some servers see this header, they automatically refrain
from using the chunked encoding for responses of unknown length, while this
is totally unrelated. The immediate effect is that this prevents HAProxy from
maintaining the client connection alive. A second effect is that a client or
a cache could receive an incomplete response without being aware of it, and
consider the response complete.
By setting "option http-pretend-keepalive", HAProxy will make the server
believe it will keep the connection alive. The server will then not fall back
to the abnormal undesired above. When HAProxy gets the whole response, it
will close the connection with the server just as it would do with the
"option httpclose". That way the client gets a normal response and the
connection is correctly closed on the server side.
It is recommended not to enable this option by default, because most servers
will more efficiently close the connection themselves after the last packet,
and release its buffers slightly earlier. Also, the added packet on the
network could slightly reduce the overall peak performance. However it is
worth noting that when this option is enabled, HAProxy will have slightly
less work to do. So if HAProxy is the bottleneck on the whole architecture,
enabling this option might save a few CPU cycles.
This option may be set in backend and listen sections. Using it in a frontend
section will be ignored and a warning will be reported during startup. It is
a backend related option, so there is no real reason to set it on a
frontend. This option may be combined with "option httpclose", which will
cause keepalive to be announced to the server and close to be announced to
the client. This practice is discouraged though.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option httpclose", "
option http-server-close", and "
option http-keep-alive"
option http-server-close
no option http-server-close
Enable or disable HTTP connection closing on the server side
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and
the start of a new request. This mode may be changed by several options such
as "option http-server-close" or "option httpclose". Setting "option
http-server-close" enables HTTP connection-close mode on the server side
while keeping the ability to support HTTP keep-alive and pipelining on the
client side. This provides the lowest latency on the client side (slow
network) and the fastest session reuse on the server side to save server
resources, similarly to "option httpclose". It also permits non-keepalive
capable servers to be served in keep-alive mode to the clients if they
conform to the requirements of RFC7230. Please note that some servers do not
always conform to those requirements when they see "Connection: close" in the
request. The effect will be that keep-alive will never be used. A workaround
consists in enabling "option http-pretend-keepalive".
At the moment, logs will not indicate whether requests came from the same
session or not. The accept date reported in the logs corresponds to the end
of the previous request, and the request time corresponds to the time spent
waiting for a new request. The keep-alive request time is still bound to the
timeout defined by "timeout http-keep-alive" or "timeout http-request" if
not set.
This option may be set both in a frontend and in a backend. It is enabled if
at least one of the frontend or backend holding a connection has it enabled.
It disables and replaces any previous "option httpclose" or "option
http-keep-alive". Please check section 4 ("Proxies") to see how this option
combines with others when frontend and backend options differ.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option httpclose", "
option http-pretend-keepalive", "
option http-keep-alive", and "1.1. The HTTP transaction model".
Make use of non-standard Proxy-Connection header instead of Connection
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
While RFC7230 explicitly states that HTTP/1.1 agents must use the
Connection header to indicate their wish of persistent or non-persistent
connections, both browsers and proxies ignore this header for proxied
connections and make use of the undocumented, non-standard Proxy-Connection
header instead. The issue begins when trying to put a load balancer between
browsers and such proxies, because there will be a difference between what
HAProxy understands and what the client and the proxy agree on.
By setting this option in a frontend, HAProxy can automatically switch to use
that non-standard header if it sees proxied requests. A proxied request is
defined here as one where the URI begins with neither a '/' nor a '*'. This
is incompatible with the HTTP tunnel mode. Note that this option can only be
specified in a frontend and will affect the request along its whole life.
Also, when this option is set, a request which requires authentication will
automatically switch to use proxy authentication headers if it is itself a
proxied request. That makes it possible to check or enforce authentication in
front of an existing proxy.
This option should normally never be used, except in front of a proxy.
See also : "
option httpclose", and "
option http-server-close".
option httpchk
option httpchk <uri>
option httpchk <method> <uri>
option httpchk <method> <uri> <version>
Enables HTTP protocol to check on the servers health
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<method> is the optional HTTP method used with the requests. When not set,
the "OPTIONS" method is used, as it generally requires low server
processing and is easy to filter out from the logs. Any method
may be used, though it is not recommended to invent non-standard
ones.
<uri> is the URI referenced in the HTTP requests. It defaults to " / "
which is accessible by default on almost any server, but may be
changed to any other URI. Query strings are permitted.
<version> is the optional HTTP version string. It defaults to "HTTP/1.0"
but some servers might behave incorrectly in HTTP 1.0, so turning
it to HTTP/1.1 may sometimes help. Note that the Host field is
mandatory in HTTP/1.1, use "http-check send" directive to add it.
By default, server health checks only consist in trying to establish a TCP
connection. When "option httpchk" is specified, a complete HTTP request is
sent once the TCP connection is established, and responses 2xx and 3xx are
considered valid, while all other ones indicate a server failure, including
the lack of any response.
Combined with "http-check" directives, it is possible to customize the
request sent during the HTTP health checks or the matching rules on the
response. It is also possible to configure a send/expect sequence, just like
with the directive "tcp-check" for TCP health checks.
The server configuration is used by default to open connections to perform
HTTP health checks. By it is also possible to overwrite server parameters
using "http-check connect" rules.
"httpchk" option does not necessarily require an HTTP backend, it also works
with plain TCP backends. This is particularly useful to check simple scripts
bound to some dedicated ports using the inetd daemon. However, it will always
internally relies on an HTX multiplexer. Thus, it means the request
formatting and the response parsing will be strict.
Note : For a while, there was no way to add headers or body in the request
used for HTTP health checks. So a workaround was to hide it at the end
of the version string with a "\r\n" after the version. It is now
deprecated. The directive "http-check send" must be used instead.
Examples :
backend https_relay
mode tcp
option httpchk OPTIONS * HTTP/1.1
http-check send hdr Host www
server apache1 192.168.1.1:443 check port 80
See also : "
option ssl-hello-chk", "
option smtpchk", "
option mysql-check", "
option pgsql-check", "
http-check" and the "
check", "
port" and "
inter" server options.
option httpclose
no option httpclose
Enable or disable HTTP connection closing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and
the start of a new request. This mode may be changed by several options such
as "option http-server-close" or "option httpclose".
If "option httpclose" is set, HAProxy will close connections with the server
and the client as soon as the request and the response are received. It will
also check if a "Connection: close" header is already set in each direction,
and will add one if missing. Any "Connection" header different from "close"
will also be removed.
This option may also be combined with "option http-pretend-keepalive", which
will disable sending of the "Connection: close" header, but will still cause
the connection to be closed once the whole response is received.
This option may be set both in a frontend and in a backend. It is enabled if
at least one of the frontend or backend holding a connection has it enabled.
It disables and replaces any previous "option http-server-close" or "option
http-keep-alive". Please check section 4 ("Proxies") to see how this option
combines with others when frontend and backend options differ.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option http-server-close" and "1.1. The HTTP transaction model".
option httplog [ clf ]
Enable logging of HTTP request, session state and timers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :clf if the "clf" argument is added, then the output format will be
the CLF format instead of HAProxy's default HTTP format. You can
use this when you need to feed HAProxy's logs through a specific
log analyzer which only support the CLF format and which is not
extensible.
By default, the log output format is very poor, as it only contains the
source and destination addresses, and the instance name. By specifying
"option httplog", each log line turns into a much richer format including,
but not limited to, the HTTP request, the connection timers, the session
status, the connections numbers, the captured headers and cookies, the
frontend, backend and server name, and of course the source address and
ports.
Specifying only "option httplog" will automatically clear the 'clf' mode
if it was set by default.
"option httplog" overrides any previous "log-format" directive.
See also : section 8 about logging.
option http_proxy
no option http_proxy
Enable or disable plain HTTP proxy mode
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
It sometimes happens that people need a pure HTTP proxy which understands
basic proxy requests without caching nor any fancy feature. In this case,
it may be worth setting up an HAProxy instance with the "option http_proxy"
set. In this mode, no server is declared, and the connection is forwarded to
the IP address and port found in the URL after the "http://" scheme.
No host address resolution is performed, so this only works when pure IP
addresses are passed. Since this option's usage perimeter is rather limited,
it will probably be used only by experts who know they need exactly it. This
is incompatible with the HTTP tunnel mode.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Example :
backend direct_forward
option httpclose
option http_proxy
See also : "
option httpclose"
option independent-streams
no option independent-streams
Enable or disable independent timeout processing for both directions
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, when data is sent over a socket, both the write timeout and the
read timeout for that socket are refreshed, because we consider that there is
activity on that socket, and we have no other means of guessing if we should
receive data or not.
While this default behavior is desirable for almost all applications, there
exists a situation where it is desirable to disable it, and only refresh the
read timeout if there are incoming data. This happens on sessions with large
timeouts and low amounts of exchanged data such as telnet session. If the
server suddenly disappears, the output data accumulates in the system's
socket buffers, both timeouts are correctly refreshed, and there is no way
to know the server does not receive them, so we don't timeout. However, when
the underlying protocol always echoes sent data, it would be enough by itself
to detect the issue using the read timeout. Note that this problem does not
happen with more verbose protocols because data won't accumulate long in the
socket buffers.
When this option is set on the frontend, it will disable read timeout updates
on data sent to the client. There probably is little use of this case. When
the option is set on the backend, it will disable read timeout updates on
data sent to the server. Doing so will typically break large HTTP posts from
slow lines, so use it with caution.
See also : "
timeout client", "
timeout server" and "
timeout tunnel"
option ldap-check
Use LDAPv3 health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
It is possible to test that the server correctly talks LDAPv3 instead of just
testing that it accepts the TCP connection. When this option is set, an
LDAPv3 anonymous simple bind message is sent to the server, and the response
is analyzed to find an LDAPv3 bind response message.
The server is considered valid only when the LDAP response contains success
resultCode (http://tools.ietf.org/html/rfc4511#section-4.1.9).
Logging of bind requests is server dependent see your documentation how to
configure it.
Example :
option ldap-check
See also : "
option httpchk"
option external-check
Use external processes for server health checks
May be used in sections :
defaults |
frontend |
listen |
backend |
It is possible to test the health of a server using an external command.
This is achieved by running the executable set using "external-check
command".
Requires the "external-check" global to be set.
See also : "
external-check", "
external-check command", "
external-check path"
option log-health-checks
no option log-health-checks
Enable or disable logging of health checks status updates
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, failed health check are logged if server is UP and successful
health checks are logged if server is DOWN, so the amount of additional
information is limited.
When this option is enabled, any change of the health check status or to
the server's health will be logged, so that it becomes possible to know
that a server was failing occasional checks before crashing, or exactly when
it failed to respond a valid HTTP status, then when the port started to
reject connections, then when the server stopped responding at all.
Note that status changes not caused by health checks (e.g. enable/disable on
the CLI) are intentionally not logged by this option.
See also: "
option httpchk", "
option ldap-check", "
option mysql-check", "
option pgsql-check", "
option redis-check", "
option smtpchk", "
option tcp-check", "
log" and
section 8 about logging.
option log-separate-errors
no option log-separate-errors
Change log level for non-completely successful connections
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
Sometimes looking for errors in logs is not easy. This option makes HAProxy
raise the level of logs containing potentially interesting information such
as errors, timeouts, retries, redispatches, or HTTP status codes 5xx. The
level changes from "info" to "err". This makes it possible to log them
separately to a different file with most syslog daemons. Be careful not to
remove them from the original file, otherwise you would lose ordering which
provides very important information.
Using this option, large sites dealing with several thousand connections per
second may log normal traffic to a rotating buffer and only archive smaller
error logs.
See also : "
log", "
dontlognull", "
dontlog-normal" and
section 8 about logging.
option logasap
no option logasap
Enable or disable early logging.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, logs are emitted when all the log format variables and sample
fetches used in the definition of the log-format string return a value, or
when the session is terminated. This allows the built in log-format strings
to account for the transfer time, or the number of bytes in log messages.
When handling long lived connections such as large file transfers or RDP,
it may take a while for the request or connection to appear in the logs.
Using "option logasap", the log message is created as soon as the server
connection is established in mode tcp, or as soon as the server sends the
complete headers in mode http. Missing information in the logs will be the
total number of bytes which will only indicate the amount of data transferred
before the message was created and the total time which will not take the
remainder of the connection life or transfer time into account. For the case
of HTTP, it is good practice to capture the Content-Length response header
so that the logs at least indicate how many bytes are expected to be
transferred.
Examples :
listen http_proxy 0.0.0.0:80
mode http
option httplog
option logasap
log 192.168.2.200 local3
>>> Feb 6 12:14:14 localhost \
haproxy[14389]: 10.0.1.2:33317 [06/Feb/2009:12:14:14.655] http-in \
static/srv1 9/10/7/14/+30 200 +243 - - ---- 3/1/1/1/0 1/0 \
"GET /image.iso HTTP/1.0"
See also : "
option httplog", "
capture response header", and
section 8 about logging.
option mysql-check [ user <username> [ { post-41 | pre-41 } ] ]
Use MySQL health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<username> This is the username which will be used when connecting to MySQL
server.
post-41 Send post v4.1 client compatible checks (the default)
pre-41 Send pre v4.1 client compatible checks
If you specify a username, the check consists of sending two MySQL packet,
one Client Authentication packet, and one QUIT packet, to correctly close
MySQL session. We then parse the MySQL Handshake Initialization packet and/or
Error packet. It is a basic but useful test which does not produce error nor
aborted connect on the server. However, it requires adding an authorization
in the MySQL table, like this :
USE mysql;
INSERT INTO user (Host,User) values ('<ip_of_haproxy>','<username>');
FLUSH PRIVILEGES;
If you don't specify a username (it is deprecated and not recommended), the
check only consists in parsing the Mysql Handshake Initialization packet or
Error packet, we don't send anything in this mode. It was reported that it
can generate lockout if check is too frequent and/or if there is not enough
traffic. In fact, you need in this case to check MySQL "max_connect_errors"
value as if a connection is established successfully within fewer than MySQL
"max_connect_errors" attempts after a previous connection was interrupted,
the error count for the host is cleared to zero. If HAProxy's server get
blocked, the "FLUSH HOSTS" statement is the only way to unblock it.
Remember that this does not check database presence nor database consistency.
To do this, you can use an external check with xinetd for example.
The check requires MySQL >=3.22, for older version, please use TCP check.
Most often, an incoming MySQL server needs to see the client's IP address for
various purposes, including IP privilege matching and connection logging.
When possible, it is often wise to masquerade the client's IP address when
connecting to the server using the "usesrc" argument of the "source" keyword,
which requires the transparent proxy feature to be compiled in, and the MySQL
server to route the client via the machine hosting HAProxy.
See also: "
option httpchk"
option nolinger
no option nolinger
Enable or disable immediate session resource cleaning after close
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When clients or servers abort connections in a dirty way (e.g. they are
physically disconnected), the session timeouts triggers and the session is
closed. But it will remain in FIN_WAIT1 state for some time in the system,
using some resources and possibly limiting the ability to establish newer
connections.
When this happens, it is possible to activate "option nolinger" which forces
the system to immediately remove any socket's pending data on close. Thus,
a TCP RST is emitted, any pending data are truncated, and the session is
instantly purged from the system's tables. The generally visible effect for
a client is that responses are truncated if the close happens with a last
block of data (e.g. on a redirect or error response). On the server side,
it may help release the source ports immediately when forwarding a client
aborts in tunnels. In both cases, TCP resets are emitted and given that
the session is instantly destroyed, there will be no retransmit. On a lossy
network this can increase problems, especially when there is a firewall on
the lossy side, because the firewall might see and process the reset (hence
purge its session) and block any further traffic for this session,, including
retransmits from the other side. So if the other side doesn't receive it,
it will never receive any RST again, and the firewall might log many blocked
packets.
For all these reasons, it is strongly recommended NOT to use this option,
unless absolutely needed as a last resort. In most situations, using the
"client-fin" or "server-fin" timeouts achieves similar results with a more
reliable behavior. On Linux it's also possible to use the "tcp-ut" bind or
server setting.
This option may be used both on frontends and backends, depending on the side
where it is required. Use it on the frontend for clients, and on the backend
for servers. While this option is technically supported in "defaults"
sections, it must really not be used there as it risks to accidentally
propagate to sections that must no use it and to cause problems there.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also: "
timeout client-fin", "
timeout server-fin", "
tcp-ut" bind or server keywords.
option originalto [ except <network> ] [ header <name> ]
Enable insertion of the X-Original-To header to requests sent to servers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<network> is an optional argument used to disable this option for sources
matching <network>
<name> an optional argument to specify a different "X-Original-To"
header name.
Since HAProxy can work in transparent mode, every request from a client can
be redirected to the proxy and HAProxy itself can proxy every request to a
complex SQUID environment and the destination host from SO_ORIGINAL_DST will
be lost. This is annoying when you want access rules based on destination ip
addresses. To solve this problem, a new HTTP header "X-Original-To" may be
added by HAProxy to all requests sent to the server. This header contains a
value representing the original destination IP address. Since this must be
configured to always use the last occurrence of this header only. Note that
only the last occurrence of the header must be used, since it is really
possible that the client has already brought one.
The keyword "header" may be used to supply a different header name to replace
the default "X-Original-To". This can be useful where you might already
have a "X-Original-To" header from a different application, and you need
preserve it. Also if your backend server doesn't use the "X-Original-To"
header and requires different one.
Sometimes, a same HAProxy instance may be shared between a direct client
access and a reverse-proxy access (for instance when an SSL reverse-proxy is
used to decrypt HTTPS traffic). It is possible to disable the addition of the
header for a known destination address or network by adding the "except"
keyword followed by the network address. In this case, any destination IP
matching the network will not cause an addition of this header. Most common
uses are with private networks or 127.0.0.1. IPv4 and IPv6 are both
supported.
This option may be specified either in the frontend or in the backend. If at
least one of them uses it, the header will be added. Note that the backend's
setting of the header subargument takes precedence over the frontend's if
both are defined.
Examples :
frontend www
mode http
option originalto except 127.0.0.1
backend www
mode http
option originalto header X-Client-Dst
See also : "
option httpclose", "
option http-server-close".
option persist
no option persist
Enable or disable forced persistence on down servers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When an HTTP request reaches a backend with a cookie which references a dead
server, by default it is redispatched to another server. It is possible to
force the request to be sent to the dead server first using "option persist"
if absolutely needed. A common use case is when servers are under extreme
load and spend their time flapping. In this case, the users would still be
directed to the server they opened the session on, in the hope they would be
correctly served. It is recommended to use "option redispatch" in conjunction
with this option so that in the event it would not be possible to connect to
the server at all (server definitely dead), the client would finally be
redirected to another valid server.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option redispatch", "
retries", "
force-persist"
option pgsql-check [ user <username> ]
Use PostgreSQL health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<username> This is the username which will be used when connecting to
PostgreSQL server.
The check sends a PostgreSQL StartupMessage and waits for either
Authentication request or ErrorResponse message. It is a basic but useful
test which does not produce error nor aborted connect on the server.
This check is identical with the "mysql-check".
See also: "
option httpchk"
option prefer-last-server
no option prefer-last-server
Allow multiple load balanced requests to remain on the same server
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When the load balancing algorithm in use is not deterministic, and a previous
request was sent to a server to which HAProxy still holds a connection, it is
sometimes desirable that subsequent requests on a same session go to the same
server as much as possible. Note that this is different from persistence, as
we only indicate a preference which HAProxy tries to apply without any form
of warranty. The real use is for keep-alive connections sent to servers. When
this option is used, HAProxy will try to reuse the same connection that is
attached to the server instead of rebalancing to another server, causing a
close of the connection. This can make sense for static file servers. It does
not make much sense to use this in combination with hashing algorithms. Note,
HAProxy already automatically tries to stick to a server which sends a 401 or
to a proxy which sends a 407 (authentication required), when the load
balancing algorithm is not deterministic. This is mandatory for use with the
broken NTLM authentication challenge, and significantly helps in
troubleshooting some faulty applications. Option prefer-last-server might be
desirable in these environments as well, to avoid redistributing the traffic
after every other response.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also: "
option http-keep-alive"
option redispatch
option redispatch <interval>
no option redispatch
Enable or disable session redistribution in case of connection failure
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<interval> The optional integer value that controls how often redispatches
occur when retrying connections. Positive value P indicates a
redispatch is desired on every Pth retry, and negative value
N indicate a redispatch is desired on the Nth retry prior to the
last retry. For example, the default of -1 preserves the
historical behavior of redispatching on the last retry, a
positive value of 1 would indicate a redispatch on every retry,
and a positive value of 3 would indicate a redispatch on every
third retry. You can disable redispatches with a value of 0.
In HTTP mode, if a server designated by a cookie is down, clients may
definitely stick to it because they cannot flush the cookie, so they will not
be able to access the service anymore.
Specifying "option redispatch" will allow the proxy to break cookie or
consistent hash based persistence and redistribute them to a working server.
Active servers are selected from a subset of the list of available
servers. Active servers that are not down or in maintenance (i.e., whose
health is not checked or that have been checked as "up"), are selected in the
following order:
1. Any active, non-backup server, if any, or,
2. If the "allbackups" option is not set, the first backup server in the
list, or
3. If the "allbackups" option is set, any backup server.
When a retry occurs, HAProxy tries to select another server than the last
one. The new server is selected from the current list of servers.
Sometimes, if the list is updated between retries (e.g., if numerous retries
occur and last longer than the time needed to check that a server is down,
remove it from the list and fall back on the list of backup servers),
connections may be redirected to a backup server, though.
It also allows to retry connections to another server in case of multiple
connection failures. Of course, it requires having "retries" set to a nonzero
value.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
retries", "
force-persist"
option redis-check
Use redis health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
It is possible to test that the server correctly talks REDIS protocol instead
of just testing that it accepts the TCP connection. When this option is set,
a PING redis command is sent to the server, and the response is analyzed to
find the "+PONG" response message.
Example :
option redis-check
See also : "
option httpchk", "
option tcp-check", "
tcp-check expect"
option smtpchk
option smtpchk <hello> <domain>
Use SMTP health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<hello> is an optional argument. It is the "hello" command to use. It can
be either "HELO" (for SMTP) or "EHLO" (for ESMTP). All other
values will be turned into the default command ("HELO").
<domain> is the domain name to present to the server. It may only be
specified (and is mandatory) if the hello command has been
specified. By default, "localhost" is used.
When "option smtpchk" is set, the health checks will consist in TCP
connections followed by an SMTP command. By default, this command is
"HELO localhost". The server's return code is analyzed and only return codes
starting with a "2" will be considered as valid. All other responses,
including a lack of response will constitute an error and will indicate a
dead server.
This test is meant to be used with SMTP servers or relays. Depending on the
request, it is possible that some servers do not log each connection attempt,
so you may want to experiment to improve the behavior. Using telnet on port
25 is often easier than adjusting the configuration.
Most often, an incoming SMTP server needs to see the client's IP address for
various purposes, including spam filtering, anti-spoofing and logging. When
possible, it is often wise to masquerade the client's IP address when
connecting to the server using the "usesrc" argument of the "source" keyword,
which requires the transparent proxy feature to be compiled in.
Example :
option smtpchk HELO mydomain.org
See also : "
option httpchk", "
source"
option socket-stats
no option socket-stats
Enable or disable collecting & providing separate statistics for each socket.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
option splice-auto
no option splice-auto
Enable or disable automatic kernel acceleration on sockets in both directions
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When this option is enabled either on a frontend or on a backend, HAProxy
will automatically evaluate the opportunity to use kernel tcp splicing to
forward data between the client and the server, in either direction. HAProxy
uses heuristics to estimate if kernel splicing might improve performance or
not. Both directions are handled independently. Note that the heuristics used
are not much aggressive in order to limit excessive use of splicing. This
option requires splicing to be enabled at compile time, and may be globally
disabled with the global option "nosplice". Since splice uses pipes, using it
requires that there are enough spare pipes.
Important note: kernel-based TCP splicing is a Linux-specific feature which
first appeared in kernel 2.6.25. It offers kernel-based acceleration to
transfer data between sockets without copying these data to user-space, thus
providing noticeable performance gains and CPU cycles savings. Since many
early implementations are buggy, corrupt data and/or are inefficient, this
feature is not enabled by default, and it should be used with extreme care.
While it is not possible to detect the correctness of an implementation,
2.6.29 is the first version offering a properly working implementation. In
case of doubt, splicing may be globally disabled using the global "nosplice"
keyword.
Example :
option splice-auto
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option splice-request", "
option splice-response", and global options "
nosplice" and "
maxpipes"
option splice-request
no option splice-request
Enable or disable automatic kernel acceleration on sockets for requests
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When this option is enabled either on a frontend or on a backend, HAProxy
will use kernel tcp splicing whenever possible to forward data going from
the client to the server. It might still use the recv/send scheme if there
are no spare pipes left. This option requires splicing to be enabled at
compile time, and may be globally disabled with the global option "nosplice".
Since splice uses pipes, using it requires that there are enough spare pipes.
Important note: see "option splice-auto" for usage limitations.
Example :
option splice-request
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option splice-auto", "
option splice-response", and global options "
nosplice" and "
maxpipes"
option splice-response
no option splice-response
Enable or disable automatic kernel acceleration on sockets for responses
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When this option is enabled either on a frontend or on a backend, HAProxy
will use kernel tcp splicing whenever possible to forward data going from
the server to the client. It might still use the recv/send scheme if there
are no spare pipes left. This option requires splicing to be enabled at
compile time, and may be globally disabled with the global option "nosplice".
Since splice uses pipes, using it requires that there are enough spare pipes.
Important note: see "option splice-auto" for usage limitations.
Example :
option splice-response
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option splice-auto", "
option splice-request", and global options "
nosplice" and "
maxpipes"
option spop-check
Use SPOP health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
It is possible to test that the server correctly talks SPOP protocol instead
of just testing that it accepts the TCP connection. When this option is set,
a HELLO handshake is performed between HAProxy and the server, and the
response is analyzed to check no error is reported.
Example :
option spop-check
See also : "
option httpchk"
option srvtcpka
no option srvtcpka
Enable or disable the sending of TCP keepalive packets on the server side
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When there is a firewall or any session-aware component between a client and
a server, and when the protocol involves very long sessions with long idle
periods (e.g. remote desktops), there is a risk that one of the intermediate
components decides to expire a session which has remained idle for too long.
Enabling socket-level TCP keep-alives makes the system regularly send packets
to the other end of the connection, leaving it active. The delay between
keep-alive probes is controlled by the system only and depends both on the
operating system and its tuning parameters.
It is important to understand that keep-alive packets are neither emitted nor
received at the application level. It is only the network stacks which sees
them. For this reason, even if one side of the proxy already uses keep-alives
to maintain its connection alive, those keep-alive packets will not be
forwarded to the other side of the proxy.
Please note that this has nothing to do with HTTP keep-alive.
Using option "srvtcpka" enables the emission of TCP keep-alive probes on the
server side of a connection, which should help when session expirations are
noticed between HAProxy and a server.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option clitcpka", "
option tcpka"
option ssl-hello-chk
Use SSLv3 client hello health checks for server testing
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When some SSL-based protocols are relayed in TCP mode through HAProxy, it is
possible to test that the server correctly talks SSL instead of just testing
that it accepts the TCP connection. When "option ssl-hello-chk" is set, pure
SSLv3 client hello messages are sent once the connection is established to
the server, and the response is analyzed to find an SSL server hello message.
The server is considered valid only when the response contains this server
hello message.
All servers tested till there correctly reply to SSLv3 client hello messages,
and most servers tested do not even log the requests containing only hello
messages, which is appreciable.
Note that this check works even when SSL support was not built into HAProxy
because it forges the SSL message. When SSL support is available, it is best
to use native SSL health checks instead of this one.
See also: "
option httpchk", "
check-ssl"
option tcp-check
Perform health checks using tcp-check send/expect sequences
May be used in sections :
defaults |
frontend |
listen |
backend |
This health check method is intended to be combined with "tcp-check" command
lists in order to support send/expect types of health check sequences.
TCP checks currently support 4 modes of operations :
- no "tcp-check" directive : the health check only consists in a connection
attempt, which remains the default mode.
- "tcp-check send" or "tcp-check send-binary" only is mentioned : this is
used to send a string along with a connection opening. With some
protocols, it helps sending a "QUIT" message for example that prevents
the server from logging a connection error for each health check. The
check result will still be based on the ability to open the connection
only.
- "tcp-check expect" only is mentioned : this is used to test a banner.
The connection is opened and HAProxy waits for the server to present some
contents which must validate some rules. The check result will be based
on the matching between the contents and the rules. This is suited for
POP, IMAP, SMTP, FTP, SSH, TELNET.
- both "tcp-check send" and "tcp-check expect" are mentioned : this is
used to test a hello-type protocol. HAProxy sends a message, the server
responds and its response is analyzed. the check result will be based on
the matching between the response contents and the rules. This is often
suited for protocols which require a binding or a request/response model.
LDAP, MySQL, Redis and SSL are example of such protocols, though they
already all have their dedicated checks with a deeper understanding of
the respective protocols.
In this mode, many questions may be sent and many answers may be
analyzed.
A fifth mode can be used to insert comments in different steps of the script.
For each tcp-check rule you create, you can add a "comment" directive,
followed by a string. This string will be reported in the log and stderr in
debug mode. It is useful to make user-friendly error reporting. The
"comment" is of course optional.
During the execution of a health check, a variable scope is made available to
store data samples, using the "tcp-check set-var" operation. Freeing those
variable is possible using "tcp-check unset-var".
Examples :
option tcp-check
tcp-check expect string +OK\ POP3\ ready comment POP\ protocol
option tcp-check
tcp-check expect string *\ OK\ IMAP4\ ready comment IMAP\ protocol
option tcp-check
tcp-check comment PING\ phase
tcp-check send PING\r\n
tcp-check expect string +PONG
tcp-check comment role\ check
tcp-check send info\ replication\r\n
tcp-check expect string role:master
tcp-check comment QUIT\ phase
tcp-check send QUIT\r\n
tcp-check expect string +OK
forge a HTTP request, then analyze the response
(send many headers before analyzing)
option tcp-check
tcp-check comment forge\ and\ send\ HTTP\ request
tcp-check send HEAD\ /\ HTTP/1.1\r\n
tcp-check send Host:\ www.mydomain.com\r\n
tcp-check send User-Agent:\ HAProxy\ tcpcheck\r\n
tcp-check send \r\n
tcp-check expect rstring HTTP/1\..\ (2..|3..) comment check\ HTTP\ response
See also : "
tcp-check connect", "
tcp-check expect" and "
tcp-check send".
option tcp-smart-accept
no option tcp-smart-accept
Enable or disable the saving of one ACK packet during the accept sequence
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When an HTTP connection request comes in, the system acknowledges it on
behalf of HAProxy, then the client immediately sends its request, and the
system acknowledges it too while it is notifying HAProxy about the new
connection. HAProxy then reads the request and responds. This means that we
have one TCP ACK sent by the system for nothing, because the request could
very well be acknowledged by HAProxy when it sends its response.
For this reason, in HTTP mode, HAProxy automatically asks the system to avoid
sending this useless ACK on platforms which support it (currently at least
Linux). It must not cause any problem, because the system will send it anyway
after 40 ms if the response takes more time than expected to come.
During complex network debugging sessions, it may be desirable to disable
this optimization because delayed ACKs can make troubleshooting more complex
when trying to identify where packets are delayed. It is then possible to
fall back to normal behavior by specifying "no option tcp-smart-accept".
It is also possible to force it for non-HTTP proxies by simply specifying
"option tcp-smart-accept". For instance, it can make sense with some services
such as SMTP where the server speaks first.
It is recommended to avoid forcing this option in a defaults section. In case
of doubt, consider setting it back to automatic values by prepending the
"default" keyword before it, or disabling it using the "no" keyword.
See also : "
option tcp-smart-connect"
option tcp-smart-connect
no option tcp-smart-connect
Enable or disable the saving of one ACK packet during the connect sequence
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
On certain systems (at least Linux), HAProxy can ask the kernel not to
immediately send an empty ACK upon a connection request, but to directly
send the buffer request instead. This saves one packet on the network and
thus boosts performance. It can also be useful for some servers, because they
immediately get the request along with the incoming connection.
This feature is enabled when "option tcp-smart-connect" is set in a backend.
It is not enabled by default because it makes network troubleshooting more
complex.
It only makes sense to enable it with protocols where the client speaks first
such as HTTP. In other situations, if there is no data to send in place of
the ACK, a normal ACK is sent.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "
option tcp-smart-accept"
option tcpka
Enable or disable the sending of TCP keepalive packets on both sides
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
When there is a firewall or any session-aware component between a client and
a server, and when the protocol involves very long sessions with long idle
periods (e.g. remote desktops), there is a risk that one of the intermediate
components decides to expire a session which has remained idle for too long.
Enabling socket-level TCP keep-alives makes the system regularly send packets
to the other end of the connection, leaving it active. The delay between
keep-alive probes is controlled by the system only and depends both on the
operating system and its tuning parameters.
It is important to understand that keep-alive packets are neither emitted nor
received at the application level. It is only the network stacks which sees
them. For this reason, even if one side of the proxy already uses keep-alives
to maintain its connection alive, those keep-alive packets will not be
forwarded to the other side of the proxy.
Please note that this has nothing to do with HTTP keep-alive.
Using option "tcpka" enables the emission of TCP keep-alive probes on both
the client and server sides of a connection. Note that this is meaningful
only in "defaults" or "listen" sections. If this option is used in a
frontend, only the client side will get keep-alives, and if this option is
used in a backend, only the server side will get keep-alives. For this
reason, it is strongly recommended to explicitly use "option clitcpka" and
"option srvtcpka" when the configuration is split between frontends and
backends.
See also : "
option clitcpka", "
option srvtcpka"
option tcplog
Enable advanced logging of TCP connections with session state and timers
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, the log output format is very poor, as it only contains the
source and destination addresses, and the instance name. By specifying
"option tcplog", each log line turns into a much richer format including, but
not limited to, the connection timers, the session status, the connections
numbers, the frontend, backend and server name, and of course the source
address and ports. This option is useful for pure TCP proxies in order to
find which of the client or server disconnects or times out. For normal HTTP
proxies, it's better to use "option httplog" which is even more complete.
"option tcplog" overrides any previous "log-format" directive.
See also : "
option httplog", and
section 8 about logging.
option transparent
no option transparent
Enable client-side transparent proxying
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
This option was introduced in order to provide layer 7 persistence to layer 3
load balancers. The idea is to use the OS's ability to redirect an incoming
connection for a remote address to a local process (here HAProxy), and let
this process know what address was initially requested. When this option is
used, sessions without cookies will be forwarded to the original destination
IP address of the incoming request (which should match that of another
equipment), while requests with cookies will still be forwarded to the
appropriate server.
Note that contrary to a common belief, this option does NOT make HAProxy
present the client's IP to the server when establishing the connection.
See also: the "usesrc" argument of the "
source" keyword, and the "
transparent" option of the "
bind" keyword.
external-check command <command>
Executable to run when performing an external-check
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<command> is the external command to run
The arguments passed to the to the command are:
<proxy_address> <proxy_port> <server_address> <server_port>
The <proxy_address> and <proxy_port> are derived from the first listener
that is either IPv4, IPv6 or a UNIX socket. In the case of a UNIX socket
listener the proxy_address will be the path of the socket and the
<proxy_port> will be the string "NOT_USED". In a backend section, it's not
possible to determine a listener, and both <proxy_address> and <proxy_port>
will have the string value "NOT_USED".
Some values are also provided through environment variables.
Environment variables :
HAPROXY_PROXY_ADDR The first bind address if available (or empty if not
applicable, for example in a "backend" section).
HAPROXY_PROXY_ID The backend id.
HAPROXY_PROXY_NAME The backend name.
HAPROXY_PROXY_PORT The first bind port if available (or empty if not
applicable, for example in a "backend" section or
for a UNIX socket).
HAPROXY_SERVER_ADDR The server address.
HAPROXY_SERVER_CURCONN The current number of connections on the server.
HAPROXY_SERVER_ID The server id.
HAPROXY_SERVER_MAXCONN The server max connections.
HAPROXY_SERVER_NAME The server name.
HAPROXY_SERVER_PORT The server port if available (or empty for a UNIX
socket).
PATH The PATH environment variable used when executing
the command may be set using "external-check path".
See also "2.3. Environment variables" for other variables.
If the command executed and exits with a zero status then the check is
considered to have passed, otherwise the check is considered to have
failed.
Example :
external-check command /bin/true
See also : "
external-check", "
option external-check", "
external-check path"
external-check path <path>
The value of the PATH environment variable used when running an external-check
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<path> is the path used when executing external command to run
The default path is "".
Example :
external-check path "/usr/bin:/bin"
See also : "
external-check", "
option external-check", "
external-check command"
persist rdp-cookie
persist rdp-cookie(<name>)
Enable RDP cookie-based persistence
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the optional name of the RDP cookie to check. If omitted, the
default cookie name "msts" will be used. There currently is no
valid reason to change this name.
This statement enables persistence based on an RDP cookie. The RDP cookie
contains all information required to find the server in the list of known
servers. So when this option is set in the backend, the request is analyzed
and if an RDP cookie is found, it is decoded. If it matches a known server
which is still UP (or if "option persist" is set), then the connection is
forwarded to this server.
Note that this only makes sense in a TCP backend, but for this to work, the
frontend must have waited long enough to ensure that an RDP cookie is present
in the request buffer. This is the same requirement as with the "rdp-cookie"
load-balancing method. Thus it is highly recommended to put all statements in
a single "listen" section.
Also, it is important to understand that the terminal server will emit this
RDP cookie only if it is configured for "token redirection mode", which means
that the "IP address redirection" option is disabled.
Example :
listen tse-farm
bind :3389
tcp-request inspect-delay 5s
tcp-request content accept if RDP_COOKIE
persist rdp-cookie
balance rdp-cookie
server srv1 1.1.1.1:3389
server srv2 1.1.1.2:3389
See also : "balance rdp-cookie", "
tcp-request", the "req_rdp_cookie" ACL and the rdp_cookie pattern fetch function.
rate-limit sessions <rate>
Set a limit on the number of new sessions accepted per second on a frontend
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<rate> The <rate> parameter is an integer designating the maximum number
of new sessions per second to accept on the frontend.
When the frontend reaches the specified number of new sessions per second, it
stops accepting new connections until the rate drops below the limit again.
During this time, the pending sessions will be kept in the socket's backlog
(in system buffers) and HAProxy will not even be aware that sessions are
pending. When applying very low limit on a highly loaded service, it may make
sense to increase the socket's backlog using the "backlog" keyword.
This feature is particularly efficient at blocking connection-based attacks
or service abuse on fragile servers. Since the session rate is measured every
millisecond, it is extremely accurate. Also, the limit applies immediately,
no delay is needed at all to detect the threshold.
Example :
Limit the connection rate on SMTP to 10 per second max
listen smtp
mode tcp
bind :25
rate-limit sessions 10
server smtp1 127.0.0.1:1025
Note : when the maximum rate is reached, the frontend's status is not changed
but its sockets appear as "WAITING" in the statistics if the
"socket-stats" option is enabled.
See also : the "
backlog" keyword and the "
fe_sess_rate" ACL criterion.
redirect location <loc> [code <code>] <option> [{if | unless} <condition>]
redirect prefix <pfx> [code <code>] <option> [{if | unless} <condition>]
redirect scheme <sch> [code <code>] <option> [{if | unless} <condition>]
Return an HTTP redirection if/unless a condition is matched
May be used in sections :
defaults |
frontend |
listen |
backend |
If/unless the condition is matched, the HTTP request will lead to a redirect
response. If no condition is specified, the redirect applies unconditionally.
Arguments :<loc> With "redirect location", the exact value in <loc> is placed into
the HTTP "Location" header. When used in an "http-request" rule,
<loc> value follows the log-format rules and can include some
dynamic values (see Custom Log Format in section 8.2.4).
<pfx> With "redirect prefix", the "Location" header is built from the
concatenation of <pfx> and the complete URI path, including the
query string, unless the "drop-query" option is specified (see
below). As a special case, if <pfx> equals exactly "/", then
nothing is inserted before the original URI. It allows one to
redirect to the same URL (for instance, to insert a cookie). When
used in an "http-request" rule, <pfx> value follows the log-format
rules and can include some dynamic values (see Custom Log Format
in section 8.2.4).
<sch> With "redirect scheme", then the "Location" header is built by
concatenating <sch> with "://" then the first occurrence of the
"Host" header, and then the URI path, including the query string
unless the "drop-query" option is specified (see below). If no
path is found or if the path is "*", then "/" is used instead. If
no "Host" header is found, then an empty host component will be
returned, which most recent browsers interpret as redirecting to
the same host. This directive is mostly used to redirect HTTP to
HTTPS. When used in an "http-request" rule, <sch> value follows
the log-format rules and can include some dynamic values (see
Custom Log Format in section 8.2.4).
<code> The code is optional. It indicates which type of HTTP redirection
is desired. Only codes 301, 302, 303, 307 and 308 are supported,
with 302 used by default if no code is specified. 301 means
"Moved permanently", and a browser may cache the Location. 302
means "Moved temporarily" and means that the browser should not
cache the redirection. 303 is equivalent to 302 except that the
browser will fetch the location with a GET method. 307 is just
like 302 but makes it clear that the same method must be reused.
Likewise, 308 replaces 301 if the same method must be used.
<option> There are several options which can be specified to adjust the
expected behavior of a redirection :
- "drop-query"
When this keyword is used in a prefix-based redirection, then the
location will be set without any possible query-string, which is useful
for directing users to a non-secure page for instance. It has no effect
with a location-type redirect.
- "append-slash"
This keyword may be used in conjunction with "drop-query" to redirect
users who use a URL not ending with a '/' to the same one with the '/'.
It can be useful to ensure that search engines will only see one URL.
For this, a return code 301 is preferred.
- "set-cookie NAME[=value]"
A "Set-Cookie" header will be added with NAME (and optionally "=value")
to the response. This is sometimes used to indicate that a user has
been seen, for instance to protect against some types of DoS. No other
cookie option is added, so the cookie will be a session cookie. Note
that for a browser, a sole cookie name without an equal sign is
different from a cookie with an equal sign.
- "clear-cookie NAME[=]"
A "Set-Cookie" header will be added with NAME (and optionally "="), but
with the "Max-Age" attribute set to zero. This will tell the browser to
delete this cookie. It is useful for instance on logout pages. It is
important to note that clearing the cookie "NAME" will not remove a
cookie set with "NAME=value". You have to clear the cookie "NAME=" for
that, because the browser makes the difference.
Example:
Move the login URL only to HTTPS.
acl clear dst_port 80
acl secure dst_port 8080
acl login_page url_beg /login
acl logout url_beg /logout
acl uid_given url_reg /login?userid=[^&]+
acl cookie_set hdr_sub(cookie) SEEN=1
redirect prefix https://mysite.com set-cookie SEEN=1 if !cookie_set
redirect prefix https://mysite.com if login_page !secure
redirect prefix http://mysite.com drop-query if login_page !uid_given
redirect location http://mysite.com/ if !login_page secure
redirect location / clear-cookie USERID= if logout
Example:
Send redirects for request for articles without a '/'.
acl missing_slash path_reg ^/article/[^/]*$
redirect code 301 prefix / drop-query append-slash if missing_slash
Example:
Redirect all HTTP traffic to HTTPS when SSL is handled by HAProxy.
redirect scheme https if !{ ssl_fc }
Example:
Append 'www.' prefix in front of all hosts not having it
http-request redirect code 301 location \
http://www.%[hdr(host)]%[capture.req.uri] \
unless { hdr_beg(host) -i www }
See section 7 about ACL usage.
retries <value>
Set the number of retries to perform on a server after a connection failure
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<value> is the number of times a connection attempt should be retried on
a server when a connection either is refused or times out. The
default value is 3.
It is important to understand that this value applies to the number of
connection attempts, not full requests. When a connection has effectively
been established to a server, there will be no more retry.
In order to avoid immediate reconnections to a server which is restarting,
a turn-around timer of min("timeout connect", one second) is applied before
a retry occurs.
When "option redispatch" is set, the last retry may be performed on another
server even if a cookie references a different server.
See also : "
option redispatch"
retry-on [list of keywords]
Specify when to attempt to automatically retry a failed request.
This setting is only valid when "mode" is set to http and is silently ignored
otherwise.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<keywords> is a list of keywords or HTTP status codes, each representing a
type of failure event on which an attempt to retry the request
is desired. Please read the notes at the bottom before changing
this setting. The following keywords are supported :
none never retry
conn-failure retry when the connection or the SSL handshake failed
and the request could not be sent. This is the default.
empty-response retry when the server connection was closed after part
of the request was sent, and nothing was received from
the server. This type of failure may be caused by the
request timeout on the server side, poor network
condition, or a server crash or restart while
processing the request.
junk-response retry when the server returned something not looking
like a complete HTTP response. This includes partial
responses headers as well as non-HTTP contents. It
usually is a bad idea to retry on such events, which
may be caused a configuration issue (wrong server port)
or by the request being harmful to the server (buffer
overflow attack for example).
response-timeout the server timeout stroke while waiting for the server
to respond to the request. This may be caused by poor
network condition, the reuse of an idle connection
which has expired on the path, or by the request being
extremely expensive to process. It generally is a bad
idea to retry on such events on servers dealing with
heavy database processing (full scans, etc) as it may
amplify denial of service attacks.
0rtt-rejected retry requests which were sent over early data and were
rejected by the server. These requests are generally
considered to be safe to retry.
<status> any HTTP status code among "401" (Unauthorized), "403"
(Forbidden), "404" (Not Found), "408" (Request Timeout),
"425" (Too Early), "500" (Server Error), "501" (Not
Implemented), "502" (Bad Gateway), "503" (Service
Unavailable), "504" (Gateway Timeout).
all-retryable-errors
retry request for any error that are considered
retryable. This currently activates "conn-failure",
"empty-response", "junk-response", "response-timeout",
"0rtt-rejected", "500", "502", "503", and "504".
Using this directive replaces any previous settings with the new ones; it is
not cumulative.
Please note that using anything other than "none" and "conn-failure" requires
to allocate a buffer and copy the whole request into it, so it has memory and
performance impacts. Requests not fitting in a single buffer will never be
retried (see the global tune.bufsize setting).
You have to make sure the application has a replay protection mechanism built
in such as a unique transaction IDs passed in requests, or that replaying the
same request has no consequence, or it is very dangerous to use any retry-on
value beside "conn-failure" and "none". Static file servers and caches are
generally considered safe against any type of retry. Using a status code can
be useful to quickly leave a server showing an abnormal behavior (out of
memory, file system issues, etc), but in this case it may be a good idea to
immediately redispatch the connection to another server (please see "option
redispatch" for this). Last, it is important to understand that most causes
of failures are the requests themselves and that retrying a request causing a
server to misbehave will often make the situation even worse for this server,
or for the whole service in case of redispatch.
Unless you know exactly how the application deals with replayed requests, you
should not use this directive.
The default is "conn-failure".
See also: "
retries", "
option redispatch", "
tune.bufsize"
server <name> <address>[:[port]] [param*]
Declare a server in a backend
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the internal name assigned to this server. This name will
appear in logs and alerts. If "http-send-name-header" is
set, it will be added to the request header sent to the server.
<address> is the IPv4 or IPv6 address of the server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up. Address "0.0.0.0" or "*" has a special meaning.
It indicates that the connection will be forwarded to the same IP
address as the one from the client connection. This is useful in
transparent proxy architectures where the client's connection is
intercepted and HAProxy must forward to the original destination
address. This is more or less what the "transparent" keyword does
except that with a server it's possible to limit concurrency and
to report statistics. Optionally, an address family prefix may be
used before the address to force the family regardless of the
address format, which can be useful to specify a path to a unix
socket with no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only)
- 'sockpair@' -> address is the FD of a connected unix
socket or of a socketpair. During a connection, the
backend creates a pair of connected sockets, and passes
one of them over the FD. The bind part will use the
received socket as the client FD. Should be used
carefully.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment
variables. The "init-addr" setting can be used to modify the way
IP addresses should be resolved upon startup.
<port> is an optional port specification. If set, all connections will
be sent to this port. If unset, the same port the client
connected to will be used. The port may also be prefixed by a "+"
or a "-". In this case, the server's port will be determined by
adding this value to the client's port.
<param*> is a list of parameters for this server. The "server" keywords
accepts an important number of options and has a complete section
dedicated to it. Please refer to section 5 for more details.
Examples :
server first 10.1.1.1:1080 cookie first check inter 1000
server second 10.1.1.2:1080 cookie second check inter 1000
server transp ipv4@
server backup "${SRV_BACKUP}:1080" backup
server www1_dc1 "${LAN_DC1}.101:80"
server www1_dc2 "${LAN_DC2}.101:80"
Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
sun_path length is used for the address length. Some other programs
such as socat use the string length only by default. Pass the option
",unix-tightsocklen=0" to any abstract socket definition in socat to
make it compatible with HAProxy's.
See also: "
default-server", "
http-send-name-header" and
section 5 about server options
server-state-file-name [ { use-backend-name | <file> } ]
Set the server state file to read, load and apply to servers available in
this backend.
May be used in sections :
defaults |
frontend |
listen |
backend |
It only applies when the directive "load-server-state-from-file" is set to
"local". When <file> is not provided, if "use-backend-name" is used or if
this directive is not set, then backend name is used. If <file> starts with a
slash '/', then it is considered as an absolute path. Otherwise, <file> is
concatenated to the global directive "server-state-base".
Example:
The minimal configuration below would make HAProxy look for the state server file '/etc/haproxy/states/bk':
global
server-state-file-base /etc/haproxy/states
backend bk
load-server-state-from-file
See also: "
server-state-base", "
load-server-state-from-file", and "show servers state"
server-template <prefix> <num | range> <fqdn>[:<port>] [params*]
Set a template to initialize servers with shared parameters.
The names of these servers are built from <prefix> and <num | range> parameters.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments:<prefix> A prefix for the server names to be built.
<num | range>
If <num> is provided, this template initializes <num> servers
with 1 up to <num> as server name suffixes. A range of numbers
<num_low>-<num_high> may also be used to use <num_low> up to
<num_high> as server name suffixes.
<fqdn> A FQDN for all the servers this template initializes.
<port> Same meaning as "server" <port> argument (see "server" keyword).
<params*>
Remaining server parameters among all those supported by "server"
keyword.
Examples:
server-template srv 1-3 google.com:80 check
server-template srv 3 google.com:80 check
server srv1 google.com:80 check
server srv2 google.com:80 check
server srv3 google.com:80 check
source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | client | clientip } ]
source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | hdr_ip(<hdr>[,<occ>]) } ]
source <addr>[:<port>] [interface <name>]
Set the source address for outgoing connections
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<addr> is the IPv4 address HAProxy will bind to before connecting to a
server. This address is also used as a source for health checks.
The default value of 0.0.0.0 means that the system will select
the most appropriate address to reach its destination. Optionally
an address family prefix may be used before the address to force
the family regardless of the address format, which can be useful
to specify a path to a unix socket with no slash ('/'). Currently
supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only)
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment variables.
<port> is an optional port. It is normally not needed but may be useful
in some very specific contexts. The default value of zero means
the system will select a free port. Note that port ranges are not
supported in the backend. If you want to force port ranges, you
have to specify them on each "server" line.
<addr2> is the IP address to present to the server when connections are
forwarded in full transparent proxy mode. This is currently only
supported on some patched Linux kernels. When this address is
specified, clients connecting to the server will be presented
with this address, while health checks will still use the address
<addr>.
<port2> is the optional port to present to the server when connections
are forwarded in full transparent proxy mode (see <addr2> above).
The default value of zero means the system will select a free
port.
<hdr> is the name of a HTTP header in which to fetch the IP to bind to.
This is the name of a comma-separated header list which can
contain multiple IP addresses. By default, the last occurrence is
used. This is designed to work with the X-Forwarded-For header
and to automatically bind to the client's IP address as seen
by previous proxy, typically Stunnel. In order to use another
occurrence from the last one, please see the <occ> parameter
below. When the header (or occurrence) is not found, no binding
is performed so that the proxy's default IP address is used. Also
keep in mind that the header name is case insensitive, as for any
HTTP header.
<occ> is the occurrence number of a value to be used in a multi-value
header. This is to be used in conjunction with "hdr_ip(<hdr>)",
in order to specify which occurrence to use for the source IP
address. Positive values indicate a position from the first
occurrence, 1 being the first one. Negative values indicate
positions relative to the last one, -1 being the last one. This
is helpful for situations where an X-Forwarded-For header is set
at the entry point of an infrastructure and must be used several
proxy layers away. When this value is not specified, -1 is
assumed. Passing a zero here disables the feature.
<name> is an optional interface name to which to bind to for outgoing
traffic. On systems supporting this features (currently, only
Linux), this allows one to bind all traffic to the server to
this interface even if it is not the one the system would select
based on routing tables. This should be used with extreme care.
Note that using this option requires root privileges.
The "source" keyword is useful in complex environments where a specific
address only is allowed to connect to the servers. It may be needed when a
private address must be used through a public gateway for instance, and it is
known that the system cannot determine the adequate source address by itself.
An extension which is available on certain patched Linux kernels may be used
through the "usesrc" optional keyword. It makes it possible to connect to the
servers with an IP address which does not belong to the system itself. This
is called "full transparent proxy mode". For this to work, the destination
servers have to route their traffic back to this address through the machine
running HAProxy, and IP forwarding must generally be enabled on this machine.
In this "full transparent proxy" mode, it is possible to force a specific IP
address to be presented to the servers. This is not much used in fact. A more
common use is to tell HAProxy to present the client's IP address. For this,
there are two methods :
- present the client's IP and port addresses. This is the most transparent
mode, but it can cause problems when IP connection tracking is enabled on
the machine, because a same connection may be seen twice with different
states. However, this solution presents the huge advantage of not
limiting the system to the 64k outgoing address+port couples, because all
of the client ranges may be used.
- present only the client's IP address and select a spare port. This
solution is still quite elegant but slightly less transparent (downstream
firewalls logs will not match upstream's). It also presents the downside
of limiting the number of concurrent connections to the usual 64k ports.
However, since the upstream and downstream ports are different, local IP
connection tracking on the machine will not be upset by the reuse of the
same session.
This option sets the default source for all servers in the backend. It may
also be specified in a "defaults" section. Finer source address specification
is possible at the server level using the "source" server option. Refer to
section 5 for more information.
In order to work, "usesrc" requires root privileges.
Examples :
backend private
source 192.168.1.200
backend transparent_ssl1
source 192.168.1.200 usesrc clientip
backend transparent_ssl2
source 192.168.1.200 usesrc client
backend transparent_ssl3
source 192.168.1.200 usesrc clientip
backend transparent_smtp
source 0.0.0.0 usesrc clientip
backend transparent_http
source 0.0.0.0 usesrc hdr_ip(x-forwarded-for,-1)
See also : the "
source" server option in
section 5, the Tproxy patches for the Linux kernel on www.balabit.com, the "
bind" keyword.
srvtcpka-cnt <count>
Sets the maximum number of keepalive probes TCP should send before dropping
the connection on the server side.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<count> is the maximum number of keepalive probes.
This keyword corresponds to the socket option TCP_KEEPCNT. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_probes) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
See also : "
option srvtcpka", "
srvtcpka-idle", "
srvtcpka-intvl".
srvtcpka-idle <timeout>
Sets the time the connection needs to remain idle before TCP starts sending
keepalive probes, if enabled the sending of TCP keepalive packets on the
server side.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<timeout> is the time the connection needs to remain idle before TCP starts
sending keepalive probes. It is specified in seconds by default,
but can be in any other unit if the number is suffixed by the
unit, as explained at the top of this document.
This keyword corresponds to the socket option TCP_KEEPIDLE. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_time) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
See also : "
option srvtcpka", "
srvtcpka-cnt", "
srvtcpka-intvl".
srvtcpka-intvl <timeout>
Sets the time between individual keepalive probes on the server side.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<timeout> is the time between individual keepalive probes. It is specified
in seconds by default, but can be in any other unit if the number
is suffixed by the unit, as explained at the top of this
document.
This keyword corresponds to the socket option TCP_KEEPINTVL. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_intvl) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
See also : "
option srvtcpka", "
srvtcpka-cnt", "
srvtcpka-idle".
stats admin { if | unless } <cond>
Enable statistics admin level if/unless a condition is matched
May be used in sections :
defaults |
frontend |
listen |
backend |
This statement enables the statistics admin level if/unless a condition is
matched.
The admin level allows to enable/disable servers from the web interface. By
default, statistics page is read-only for security reasons.
Note : Consider not using this feature in multi-process mode (nbproc > 1)
unless you know what you do : memory is not shared between the
processes, which can result in random behaviors.
Currently, the POST request is limited to the buffer size minus the reserved
buffer space, which means that if the list of servers is too long, the
request won't be processed. It is recommended to alter few servers at a
time.
Example :
backend stats_localhost
stats enable
stats admin if LOCALHOST
Example :
backend stats_auth
stats enable
stats auth admin:AdMiN123
stats admin if TRUE
Example :
userlist stats-auth
group admin users admin
user admin insecure-password AdMiN123
group readonly users haproxy
user haproxy insecure-password haproxy
backend stats_auth
stats enable
acl AUTH http_auth(stats-auth)
acl AUTH_ADMIN http_auth_group(stats-auth) admin
stats http-request auth unless AUTH
stats admin if AUTH_ADMIN
See also : "
stats enable", "
stats auth", "
stats http-request", "
nbproc", "
bind-process",
section 3.4 about userlists and
section 7 about ACL usage.
stats auth <user>:<passwd>
Enable statistics with authentication and grant access to an account
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<user> is a user name to grant access to
<passwd> is the cleartext password associated to this user
This statement enables statistics with default settings, and restricts access
to declared users only. It may be repeated as many times as necessary to
allow as many users as desired. When a user tries to access the statistics
without a valid account, a "401 Forbidden" response will be returned so that
the browser asks the user to provide a valid user and password. The real
which will be returned to the browser is configurable using "stats realm".
Since the authentication method is HTTP Basic Authentication, the passwords
circulate in cleartext on the network. Thus, it was decided that the
configuration file would also use cleartext passwords to remind the users
that those ones should not be sensitive and not shared with any other account.
It is also possible to reduce the scope of the proxies which appear in the
report using "stats scope".
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats enable", "
stats realm", "
stats scope", "
stats uri"
stats enable
Enable statistics reporting with default settings
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
This statement enables statistics reporting with default settings defined
at build time. Unless stated otherwise, these settings are used :
- stats uri : /haproxy?stats
- stats realm : "HAProxy Statistics"
- stats auth : no authentication
- stats scope : no restriction
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats auth", "
stats realm", "
stats uri"
stats hide-version
Enable statistics and hide HAProxy version reporting
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
By default, the stats page reports some useful status information along with
the statistics. Among them is HAProxy's version. However, it is generally
considered dangerous to report precise version to anyone, as it can help them
target known weaknesses with specific attacks. The "stats hide-version"
statement removes the version from the statistics report. This is recommended
for public sites or any site with a weak login/password.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats auth", "
stats enable", "
stats realm", "
stats uri"
stats http-request { allow | deny | auth [realm <realm>] } [ { if | unless } <condition> ]
Access control for statistics
May be used in sections :
defaults |
frontend |
listen |
backend |
As "http-request", these set of options allow to fine control access to
statistics. Each option may be followed by if/unless and acl.
First option with matched condition (or option without condition) is final.
For "deny" a 403 error will be returned, for "allow" normal processing is
performed, for "auth" a 401/407 error code is returned so the client
should be asked to enter a username and password.
There is no fixed limit to the number of http-request statements per
instance.
See also : "
http-request",
section 3.4 about userlists and
section 7 about ACL usage.
stats realm <realm>
Enable statistics and set authentication realm
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<realm> is the name of the HTTP Basic Authentication realm reported to
the browser. The browser uses it to display it in the pop-up
inviting the user to enter a valid username and password.
The realm is read as a single word, so any spaces in it should be escaped
using a backslash ('\').
This statement is useful only in conjunction with "stats auth" since it is
only related to authentication.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats auth", "
stats enable", "
stats uri"
stats refresh <delay>
Enable statistics with automatic refresh
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<delay> is the suggested refresh delay, specified in seconds, which will
be returned to the browser consulting the report page. While the
browser is free to apply any delay, it will generally respect it
and refresh the page this every seconds. The refresh interval may
be specified in any other non-default time unit, by suffixing the
unit after the value, as explained at the top of this document.
This statement is useful on monitoring displays with a permanent page
reporting the load balancer's activity. When set, the HTML report page will
include a link "refresh"/"stop refresh" so that the user can select whether
they want automatic refresh of the page or not.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats auth", "
stats enable", "
stats realm", "
stats uri"
stats scope { <name> | "." }
Enable statistics and limit access scope
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<name> is the name of a listen, frontend or backend section to be
reported. The special name "." (a single dot) designates the
section in which the statement appears.
When this statement is specified, only the sections enumerated with this
statement will appear in the report. All other ones will be hidden. This
statement may appear as many times as needed if multiple sections need to be
reported. Please note that the name checking is performed as simple string
comparisons, and that it is never checked that a give section name really
exists.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats auth", "
stats enable", "
stats realm", "
stats uri"
stats show-desc [ <desc> ]
Enable reporting of a description on the statistics page.
May be used in sections :
defaults |
frontend |
listen |
backend |
<desc> is an optional description to be reported. If unspecified, the
description from global section is automatically used instead.
This statement is useful for users that offer shared services to their
customers, where node or description should be different for each customer.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. By default description is not shown.
Example :
backend private_monitoring
stats enable
stats show-desc Master node for Europe, Asia, Africa
stats uri /admin?stats
stats refresh 5s
See also: "show-node", "
stats enable", "
stats uri" and "
description" in global section.
stats show-legends
Enable reporting additional information on the statistics page
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
Enable reporting additional information on the statistics page :
- cap: capabilities (proxy)
- mode: one of tcp, http or health (proxy)
- id: SNMP ID (proxy, socket, server)
- IP (socket, server)
- cookie (backend, server)
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. Default behavior is not to show this information.
See also: "
stats enable", "
stats uri".
stats show-modules
Enable display of extra statistics module on the statistics page
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : none
New columns are added at the end of the line containing the extra statistics
values as a tooltip.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. Default behavior is not to show this information.
See also: "
stats enable", "
stats uri".
stats show-node [ <name> ]
Enable reporting of a host name on the statistics page.
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments:<name> is an optional name to be reported. If unspecified, the
node name from global section is automatically used instead.
This statement is useful for users that offer shared services to their
customers, where node or description might be different on a stats page
provided for each customer. Default behavior is not to show host name.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example:
backend private_monitoring
stats enable
stats show-node Europe-1
stats uri /admin?stats
stats refresh 5s
See also: "show-desc", "
stats enable", "
stats uri", and "
node" in global section.
stats uri <prefix>
Enable statistics and define the URI prefix to access them
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<prefix> is the prefix of any URI which will be redirected to stats. This
prefix may contain a question mark ('?') to indicate part of a
query string.
The statistics URI is intercepted on the relayed traffic, so it appears as a
page within the normal application. It is strongly advised to ensure that the
selected URI will never appear in the application, otherwise it will never be
possible to reach it in the application.
The default URI compiled in HAProxy is "/haproxy?stats", but this may be
changed at build time, so it's better to always explicitly specify it here.
It is generally a good idea to include a question mark in the URI so that
intermediate proxies refrain from caching the results. Also, since any string
beginning with the prefix will be accepted as a stats request, the question
mark helps ensuring that no valid URI will begin with the same words.
It is sometimes very convenient to use "/" as the URI prefix, and put that
statement in a "listen" instance of its own. That makes it easy to dedicate
an address or a port to statistics only.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "
stats auth", "
stats enable", "
stats realm"
stick match <pattern> [table <table>] [{if | unless} <cond>]
Define a request pattern matching condition to stick a user to a server
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<pattern> is a sample expression rule as described in section 7.3. It
describes what elements of the incoming request or connection
will be analyzed in the hope to find a matching entry in a
stickiness table. This rule is mandatory.
<table> is an optional stickiness table name. If unspecified, the same
backend's table is used. A stickiness table is declared using
the "stick-table" statement.
<cond> is an optional matching condition. It makes it possible to match
on a certain criterion only when other conditions are met (or
not met). For instance, it could be used to match on a source IP
address except when a request passes through a known proxy, in
which case we'd match on a header containing that IP address.
Some protocols or applications require complex stickiness rules and cannot
always simply rely on cookies nor hashing. The "stick match" statement
describes a rule to extract the stickiness criterion from an incoming request
or connection. See section 7 for a complete list of possible patterns and
transformation rules.
The table has to be declared using the "stick-table" statement. It must be of
a type compatible with the pattern. By default it is the one which is present
in the same backend. It is possible to share a table with other backends by
referencing it using the "table" keyword. If another table is referenced,
the server's ID inside the backends are used. By default, all server IDs
start at 1 in each backend, so the server ordering is enough. But in case of
doubt, it is highly recommended to force server IDs using their "id" setting.
It is possible to restrict the conditions where a "stick match" statement
will apply, using "if" or "unless" followed by a condition. See section 7 for
ACL based conditions.
There is no limit on the number of "stick match" statements. The first that
applies and matches will cause the request to be directed to the same server
as was used for the request which created the entry. That way, multiple
matches can be used as fallbacks.
The stick rules are checked after the persistence cookies, so they will not
affect stickiness if a cookie has already been used to select a server. That
way, it becomes very easy to insert cookies and match on IP addresses in
order to maintain stickiness between HTTP and HTTPS.
Note : Consider not using this feature in multi-process mode (nbproc > 1)
unless you know what you do : memory is not shared between the
processes, which can result in random behaviors.
Example :
backend pop
mode tcp
balance roundrobin
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:110
server s2 192.168.1.1:110
backend smtp
mode tcp
balance roundrobin
stick match src table pop
server s1 192.168.1.1:25
server s2 192.168.1.1:25
See also : "
stick-table", "
stick on", "
nbproc", "
bind-process" and
section 7 about ACLs and samples fetching.
stick on <pattern> [table <table>] [{if | unless} <condition>]
Define a request pattern to associate a user to a server
May be used in sections :
defaults |
frontend |
listen |
backend |
Note : This form is exactly equivalent to "stick match" followed by
"stick store-request", all with the same arguments. Please refer
to both keywords for details. It is only provided as a convenience
for writing more maintainable configurations.
Note : Consider not using this feature in multi-process mode (nbproc > 1)
unless you know what you do : memory is not shared between the
processes, which can result in random behaviors.
Examples :
stick on src table pop if !localhost
stick match src table pop if !localhost
stick store-request src table pop if !localhost
backend http
mode http
balance roundrobin
stick on src table https
cookie SRV insert indirect nocache
server s1 192.168.1.1:80 cookie s1
server s2 192.168.1.1:80 cookie s2
backend https
mode tcp
balance roundrobin
stick-table type ip size 200k expire 30m
stick on src
server s1 192.168.1.1:443
server s2 192.168.1.1:443
See also : "
stick match", "
stick store-request", "
nbproc" and "
bind-process".
stick store-request <pattern> [table <table>] [{if | unless} <condition>]
Define a request pattern used to create an entry in a stickiness table
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments :<pattern> is a sample expression rule as described in section 7.3. It
describes what elements of the incoming request or connection
will be analyzed, extracted and stored in the table once a
server is selected.
<table> is an optional stickiness table name. If unspecified, the same
backend's table is used. A stickiness table is declared using
the "stick-table" statement.
<cond> is an optional storage condition. It makes it possible to store
certain criteria only when some conditions are met (or not met).
For instance, it could be used to store the source IP address
except when the request passes through a known proxy, in which
case we'd store a converted form of a header containing that IP
address.
Some protocols or applications require complex stickiness rules and cannot
always simply rely on cookies nor hashing. The "stick store-request" statement
describes a rule to decide what to extract from the request and when to do
it, in order to store it into a stickiness table for further requests to
match it using the "stick match" statement. Obviously the extracted part must
make sense and have a chance to be matched in a further request. Storing a
client's IP address for instance often makes sense. Storing an ID found in a
URL parameter also makes sense. Storing a source port will almost never make
any sense because it will be randomly matched. See section 7 for a complete
list of possible patterns and transformation rules.
The table has to be declared using the "stick-table" statement. It must be of
a type compatible with the pattern. By default it is the one which is present
in the same backend. It is possible to share a table with other backends by
referencing it using the "table" keyword. If another table is referenced,
the server's ID inside the backends are used. By default, all server IDs
start at 1 in each backend, so the server ordering is enough. But in case of
doubt, it is highly recommended to force server IDs using their "id" setting.
It is possible to restrict the conditions where a "stick store-request"
statement will apply, using "if" or "unless" followed by a condition. This
condition will be evaluated while parsing the request, so any criteria can be
used. See section 7 for ACL based conditions.
There is no limit on the number of "stick store-request" statements, but
there is a limit of 8 simultaneous stores per request or response. This
makes it possible to store up to 8 criteria, all extracted from either the
request or the response, regardless of the number of rules. Only the 8 first
ones which match will be kept. Using this, it is possible to feed multiple
tables at once in the hope to increase the chance to recognize a user on
another protocol or access method. Using multiple store-request rules with
the same table is possible and may be used to find the best criterion to rely
on, by arranging the rules by decreasing preference order. Only the first
extracted criterion for a given table will be stored. All subsequent store-
request rules referencing the same table will be skipped and their ACLs will
not be evaluated.
The "store-request" rules are evaluated once the server connection has been
established, so that the table will contain the real server that processed
the request.
Note : Consider not using this feature in multi-process mode (nbproc > 1)
unless you know what you do : memory is not shared between the
processes, which can result in random behaviors.
Example :
backend pop
mode tcp
balance roundrobin
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:110
server s2 192.168.1.1:110
backend smtp
mode tcp
balance roundrobin
stick match src table pop
server s1 192.168.1.1:25
server s2 192.168.1.1:25
See also : "
stick-table", "
stick on", "
nbproc", "
bind-process" and
section 7 about ACLs and sample fetching.
stick-table type {ip | integer | string [len <length>] | binary [len <length>]} size <size> [expire <expire>] [nopurge] [peers <peersect>] [srvkey <srvkey>] [store <data_type>]*
Configure the stickiness table for the current section
May be used in sections :
defaults |
frontend |
listen |
backend |
Arguments : ip a table declared with "type ip" will only store IPv4 addresses.
This form is very compact (about 50 bytes per entry) and allows
very fast entry lookup and stores with almost no overhead. This
is mainly used to store client source IP addresses.
ipv6 a table declared with "type ipv6" will only store IPv6 addresses.
This form is very compact (about 60 bytes per entry) and allows
very fast entry lookup and stores with almost no overhead. This
is mainly used to store client source IP addresses.
integer a table declared with "type integer" will store 32bit integers
which can represent a client identifier found in a request for
instance.
string a table declared with "type string" will store substrings of up
to <len> characters. If the string provided by the pattern
extractor is larger than <len>, it will be truncated before
being stored. During matching, at most <len> characters will be
compared between the string in the table and the extracted
pattern. When not specified, the string is automatically limited
to 32 characters.
binary a table declared with "type binary" will store binary blocks
of <len> bytes. If the block provided by the pattern
extractor is larger than <len>, it will be truncated before
being stored. If the block provided by the sample expression
is shorter than <len>, it will be padded by 0. When not
specified, the block is automatically limited to 32 bytes.
<length> is the maximum number of characters that will be stored in a
"string" type table (See type "string" above). Or the number
of bytes of the block in "binary" type table. Be careful when
changing this parameter as memory usage will proportionally
increase.
<size> is the maximum number of entries that can fit in the table. This
value directly impacts memory usage. Count approximately
50 bytes per entry, plus the size of a string if any. The size
supports suffixes "k", "m", "g" for 2^10, 2^20 and 2^30 factors.
[nopurge] indicates that we refuse to purge older entries when the table
is full. When not specified and the table is full when HAProxy
wants to store an entry in it, it will flush a few of the oldest
entries in order to release some space for the new ones. This is
most often the desired behavior. In some specific cases, it
be desirable to refuse new entries instead of purging the older
ones. That may be the case when the amount of data to store is
far above the hardware limits and we prefer not to offer access
to new clients than to reject the ones already connected. When
using this parameter, be sure to properly set the "expire"
parameter (see below).
<peersect> is the name of the peers section to use for replication. Entries
which associate keys to server IDs are kept synchronized with
the remote peers declared in this section. All entries are also
automatically learned from the local peer (old process) during a
soft restart.
NOTE : each peers section may be referenced only by tables
belonging to the same unique process.
<expire> defines the maximum duration of an entry in the table since it
was last created, refreshed or matched. The expiration delay is
defined using the standard time format, similarly as the various
timeouts. The maximum duration is slightly above 24 days. See
section 2.5 for more information. If this delay is not specified,
the session won't automatically expire, but older entries will
be removed once full. Be sure not to use the "nopurge" parameter
if not expiration delay is specified.
<srvkey> specifies how each server is identified for the purposes of the
stick table. The valid values are "name" and "addr". If "name" is
given, then <name> argument for the server (may be generated by
a template). If "addr" is given, then the server is identified
by its current network address, including the port. "addr" is
especially useful if you are using service discovery to generate
the addresses for servers with peered stick-tables and want
to consistently use the same host across peers for a stickiness
token.
<data_type> is used to store additional information in the stick-table. This
may be used by ACLs in order to control various criteria related
to the activity of the client matching the stick-table. For each
item specified here, the size of each entry will be inflated so
that the additional data can fit. Several data types may be
stored with an entry. Multiple data types may be specified after
the "store" keyword, as a comma-separated list. Alternatively,
it is possible to repeat the "store" keyword followed by one or
several data types. Except for the "server_id" type which is
automatically detected and enabled, all data types must be
explicitly declared to be stored. If an ACL references a data
type which is not stored, the ACL will simply not match. Some
data types require an argument which must be passed just after
the type between parenthesis. See below for the supported data
types and their arguments.
The data types that can be stored with an entry are the following :
- server_id : this is an integer which holds the numeric ID of the server a
request was assigned to. It is used by the "stick match", "stick store",
and "stick on" rules. It is automatically enabled when referenced.
- gpc0 : first General Purpose Counter. It is a positive 32-bit integer
integer which may be used for anything. Most of the time it will be used
to put a special tag on some entries, for instance to note that a
specific behavior was detected and must be known for future matches.
- gpc0_rate(<period>) : increment rate of the first General Purpose Counter
over a period. It is a positive 32-bit integer integer which may be used
for anything. Just like <gpc0>, it counts events, but instead of keeping
a cumulative number, it maintains the rate at which the counter is
incremented. Most of the time it will be used to measure the frequency of
occurrence of certain events (e.g. requests to a specific URL).
- gpc1 : second General Purpose Counter. It is a positive 32-bit integer
integer which may be used for anything. Most of the time it will be used
to put a special tag on some entries, for instance to note that a
specific behavior was detected and must be known for future matches.
- gpc1_rate(<period>) : increment rate of the second General Purpose Counter
over a period. It is a positive 32-bit integer integer which may be used
for anything. Just like <gpc1>, it counts events, but instead of keeping
a cumulative number, it maintains the rate at which the counter is
incremented. Most of the time it will be used to measure the frequency of
occurrence of certain events (e.g. requests to a specific URL).
- conn_cnt : Connection Count. It is a positive 32-bit integer which counts
the absolute number of connections received from clients which matched
this entry. It does not