ansible.builtin.constructed inventory – Uses Jinja2 to construct vars and groups based on existing inventory.
Note
This inventory plugin is part of ansible-core
and included in all Ansible
installations. In most cases, you can use the short
plugin name
constructed
even without specifying the collections:
keyword.
However, we recommend you use the FQCN for easy linking to the
plugin documentation and to avoid conflicting with other collections that may have
the same inventory plugin name.
New in Ansible 2.4
Synopsis
Uses a YAML configuration file with a valid YAML or
.config
extension to define var expressions and group conditionalsThe 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 |
Comments |
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Create vars from jinja2 expressions. Default: |
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Add hosts to group based on Jinja2 conditionals. Default: |
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Add hosts to group based on the values of a variable. Default: |
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The default value when the host variable’s value is an empty string. This option is mutually exclusive with |
|
The key from input dictionary used to generate groups |
|
parent group for keyed group |
|
A keyed group name will start with this prefix Default: |
|
separator used to build the keyed group name Default: |
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Set this option to False to omit the This option is mutually exclusive with Choices:
|
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Use in conjunction with keyed_groups. By default, a keyed group that does not have a prefix or a separator provided will have a name that starts with an underscore. This is because the default prefix is “” and the default separator is “_”. Set this option to False to omit the leading underscore (or other separator) if no prefix is given. If the group name is derived from a mapping the separator is still used to concatenate the items. To not use a separator in the group name at all, set the separator for the keyed group to an empty string instead. Choices:
|
|
token that ensures this is a source file for the ‘constructed’ plugin. Choices:
|
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If Since it is possible to use facts in the expressions they might not always be available and we ignore those errors by default. Choices:
|
|
Merge extra vars into the available variables for composition (highest precedence). Choices:
Configuration:
|
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Normally, for performance reasons, vars plugins get executed after the inventory sources complete the base inventory, this option allows for getting vars related to hosts/groups from those plugins. The host_group_vars (enabled by default) ‘vars plugin’ is the one responsible for reading host_vars/ and group_vars/ directories. This will execute all vars plugins, even those that are not supposed to execute at the ‘inventory’ stage. See vars plugins docs for details on ‘stage’. Choices:
|
Examples
# inventory.config file in YAML format
plugin: ansible.builtin.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
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.