constructed - Uses Jinja2 to construct vars and groups based on existing inventory.

New in version 2.4.

Synopsis

  • Uses a YAML configuration file with a valid YAML or .config extension to define var expressions and group conditionals
  • The Jinja2 conditionals that qualify a host for membership.
  • The JInja2 exprpessions are calculated and assigned to the variables
  • Only variables already available from previous inventories or the fact cache can be used for templating.
  • When strict is False, failed expressions will be ignored (assumes vars were missing).

Parameters

Parameter Choices/Defaults Configuration Comments
compose Default:
{}
create vars from jinja2 expressions
groups Default:
{}
add hosts to group based on Jinja2 conditionals
keyed_groups Default:
[]
add hosts to group based on the values of a variable
strict Default:
no
If true make invalid entries a fatal error, otherwise skip and continue
Since it is possible to use facts in the expressions they might not always be available and we ignore those errors by default.

Examples

# inventory.config file in YAML format
plugin: constructed
strict: False
compose:
    var_sum: var1 + var2

    # this variable will only be set if I have a persistent fact cache enabled (and have non expired facts)
    # `strict: False` will skip this instead of producing an error if it is missing facts.
    server_type: "ansible_hostname | regex_replace ('(.{6})(.{2}).*', '\2')"
groups:
    # simple name matching
    webservers: inventory_hostname.startswith('web')

    # using ec2 'tags' (assumes aws inventory)
    development: "'devel' in (ec2_tags|list)"

    # using other host properties populated in inventory
    private_only: not (public_dns_name is defined or ip_address is defined)

    # complex group membership
    multi_group: (group_names|intersection(['alpha', 'beta', 'omega']))|length >= 2

keyed_groups:
    # this creates a group per distro (distro_CentOS, distro_Debian) and assigns the hosts that have matching values to it,
    # using the default separator "_"
    - prefix: distro
      key: ansible_distribution

    # this creates a group per ec2 architecture and assign hosts to the matching ones (arch_x86_64, arch_sparc, etc)
    - prefix: arch
      key: ec2_architecture

Status

Author

  • UNKNOWN

Hint

If you notice any issues in this documentation you can edit this document to improve it.

© 2012–2018 Michael DeHaan
© 2018–2019 Red Hat, Inc.
Licensed under the GNU General Public License version 3.
https://docs.ansible.com/ansible/2.5/plugins/inventory/constructed.html