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 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
Default:
[]
Add hosts to group based on the values of a variable.
plugin
- / required
    Choices:
  • constructed
token that ensures this is a source file for the 'constructed' plugin.
strict
boolean
    Choices:
  • 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 contrib/inventory/ec2.py
    # 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

    # this creates a group per ec2 region like "us_west_1"
    - prefix: ""
      separator: ""
      key: ec2_region

    # this creates a common parent group for all ec2 availability zones
    - key: ec2_placement
      parent_group: all_ec2_zones

Status

Authors

  • UNKNOWN

Hint

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

Hint

Configuration entries for each entry type have a low to high priority order. For example, a variable that is lower in the list will override a variable that is higher up.