ansible.builtin.constructed – Uses Jinja2 to construct vars and groups based on existing inventory.

• Synopsis
• Parameters
• Examples

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 expressions 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

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 | intersect(['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

    # the following examples assume the first inventory is from the `aws_ec2` plugin
    # this creates a group per ec2 architecture and assign hosts to the matching ones (arch_x86_64, arch_sparc, etc)
    - prefix: arch
      key: architecture

    # this creates a group per ec2 region like "us_west_1"
    - prefix: ""
      separator: ""
      key: placement.region

    # this creates a common parent group for all ec2 availability zones
    - key: placement.availability_zone
      parent_group: all_ec2_zones