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

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< Inventory PluginsAnsible/docs/2.8/plugins/inventory/constructed


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

  • 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|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

    # 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.


© 2012–2018 Michael DeHaan
© 2018–2019 Red Hat, Inc.
Licensed under the GNU General Public License version 3.
https://docs.ansible.com/ansible/2.8/plugins/inventory/constructed.html