Inventory Plugins

Enabling inventory plugins
Using inventory plugins
Plugin List

Inventory plugins allow users to point at data sources to compile the inventory of hosts that Ansible uses to target tasks, either via the -i /path/to/file and/or -i 'host1, host2' command line parameters or from other configuration sources.

Enabling inventory plugins

Most inventory plugins shipped with Ansible are disabled by default and need to be whitelisted in your ansible.cfg file in order to function. This is how the default whitelist looks in the config file that ships with Ansible:

[inventory]
enable_plugins = host_list, script, auto, yaml, ini, toml

This list also establishes the order in which each plugin tries to parse an inventory source. Any plugins left out of the list will not be considered, so you can ‘optimize’ your inventory loading by minimizing it to what you actually use. For example:

[inventory]
enable_plugins = advanced_host_list, constructed, yaml

Using inventory plugins

The only requirement for using an inventory plugin after it is enabled is to provide an inventory source to parse. Ansible will try to use the list of enabled inventory plugins, in order, against each inventory source provided. Once an inventory plugin succeeds at parsing a source, any remaining inventory plugins will be skipped for that source.

To start using an inventory plugin with a YAML configuration source, create a file with the accepted filename schema for the plugin in question, then add plugin: plugin_name. Each plugin documents any naming restrictions. For example, the aws_ec2 inventory plugin has to end with aws_ec2.(yml|yaml)

# demo.aws_ec2.yml
plugin: aws_ec2

Or for the openstack plugin the file has to be called clouds.yml or openstack.(yml|yaml):

# clouds.yml or openstack.(yml|yaml)
plugin: openstack

The auto inventory plugin is enabled by default and works by using the plugin field to indicate the plugin that should attempt to parse it. You can configure the whitelist/precedence of inventory plugins used to parse source using the ansible.cfg [‘inventory’] enable_plugins list. After enabling the plugin and providing any required options, you can view the populated inventory with ansible-inventory -i demo.aws_ec2.yml --graph:

@all:
  |--@aws_ec2:
  |  |--ec2-12-345-678-901.compute-1.amazonaws.com
  |  |--ec2-98-765-432-10.compute-1.amazonaws.com
  |--@ungrouped:

You can set the default inventory path (via inventory in the ansible.cfg [defaults] section or the ANSIBLE_INVENTORY environment variable) to your inventory source(s). Now running ansible-inventory --graph should yield the same output as when you passed your YAML configuration source(s) directly. You can add custom inventory plugins to your plugin path to use in the same way.

Your inventory source might be a directory of inventory configuration files. The constructed inventory plugin only operates on those hosts already in inventory, so you may want the constructed inventory configuration parsed at a particular point (such as last). Ansible parses the directory recursively, alphabetically. You cannot configure the parsing approach, so name your files to make it work predictably. Inventory plugins that extend constructed features directly can work around that restriction by adding constructed options in addition to the inventory plugin options. Otherwise, you can use -i with multiple sources to impose a specific order, e.g. -i demo.aws_ec2.yml -i clouds.yml -i constructed.yml.

You can create dynamic groups using host variables with the constructed keyed_groups option. The option groups can also be used to create groups and compose creates and modifies host variables. Here is an aws_ec2 example utilizing constructed features:

# demo.aws_ec2.yml
plugin: aws_ec2
regions:
  - us-east-1
  - us-east-2
keyed_groups:
  # add hosts to tag_Name_value groups for each aws_ec2 host's tags.Name variable
  - key: tags.Name
    prefix: tag_Name_
    separator: ""
groups:
  # add hosts to the group development if any of the dictionary's keys or values is the word 'devel'
  development: "'devel' in (tags|list)"
compose:
  # set the ansible_host variable to connect with the private IP address without changing the hostname
  ansible_host: private_ip_address

Now the output of ansible-inventory -i demo.aws_ec2.yml --graph:

@all:
  |--@aws_ec2:
  |  |--ec2-12-345-678-901.compute-1.amazonaws.com
  |  |--ec2-98-765-432-10.compute-1.amazonaws.com
  |  |--...
  |--@development:
  |  |--ec2-12-345-678-901.compute-1.amazonaws.com
  |  |--ec2-98-765-432-10.compute-1.amazonaws.com
  |--@tag_Name_ECS_Instance:
  |  |--ec2-98-765-432-10.compute-1.amazonaws.com
  |--@tag_Name_Test_Server:
  |  |--ec2-12-345-678-901.compute-1.amazonaws.com
  |--@ungrouped

If a host does not have the variables in the configuration above (i.e. tags.Name, tags, private_ip_address), the host will not be added to groups other than those that the inventory plugin creates and the ansible_host host variable will not be modified.

If an inventory plugin supports caching, you can enable and set caching options for an individual YAML configuration source or for multiple inventory sources using environment variables or Ansible configuration files. If you enable caching for an inventory plugin without providing inventory-specific caching options, the inventory plugin will use fact-caching options. Here is an example of enabling caching for an individual YAML configuration file:

# demo.aws_ec2.yml
plugin: aws_ec2
cache: yes
cache_plugin: jsonfile
cache_timeout: 7200
cache_connection: /tmp/aws_inventory
cache_prefix: aws_ec2

Here is an example of setting inventory caching with some fact caching defaults for the cache plugin used and the timeout in an ansible.cfg file:

[defaults]
fact_caching = json
fact_caching_connection = /tmp/ansible_facts
cache_timeout = 3600

[inventory]
cache = yes
cache_connection = /tmp/ansible_inventory

Plugin List

You can use ansible-doc -t inventory -l to see the list of available plugins. Use ansible-doc -t inventory <plugin name> to see plugin-specific documentation and examples.