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

This module is part of ansible-base and included in all Ansible installations. In most cases, you can use the short module name constructed even without specifying the collections: keyword. Despite that, we recommend you use the FQCN for easy linking to the module documentation and to avoid conflicting with other collections that may have the same module name.

New in version 2.4: of ansible.builtin

• 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

Parameter	Choices/Defaults	Configuration	Comments
compose dictionary	Default: {}		Create vars from jinja2 expressions.
groups dictionary	Default: {}		Add hosts to group based on Jinja2 conditionals.
keyed_groups list / elements=string	Default: []		Add hosts to group based on the values of a variable.
plugin string / required	constructed		token that ensures this is a source file for the 'constructed' plugin.
strict boolean	no ← yes		If yes 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 | 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

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