Lookup Plugins

• Enabling lookup plugins
• Using lookup plugins
• Forcing lookups to return lists: query and wantlist=True
• Plugin list

Lookup plugins are an Ansible-specific extension to the Jinja2 templating language. You can use lookup plugins to access data from outside sources (files, databases, key/value stores, APIs, and other services) within your playbooks. Like all templating, lookups execute and are evaluated on the Ansible control machine. Ansible makes the data returned by a lookup plugin available using the standard templating system. You can use lookup plugins to load variables or templates with information from external sources.

Enabling lookup plugins

Ansible enables all lookup plugins it can find. You can activate a custom lookup by either dropping it into a lookup_plugins directory adjacent to your play, inside the plugins/lookup/ directory of a collection you have installed, inside a standalone role, or in one of the lookup directory sources configured in ansible.cfg.

Using lookup plugins

You can use lookup plugins anywhere you can use templating in Ansible: in a play, in variables file, or in a Jinja2 template for the template module.

vars:
  file_contents: "{{ lookup('file', 'path/to/file.txt') }}"

Lookups are an integral part of loops. Wherever you see with_, the part after the underscore is the name of a lookup. For this reason, most lookups output lists and take lists as input; for example, with_items uses the items lookup:

tasks:
  - name: count to 3
    debug: msg={{ item }}
    with_items: [1, 2, 3]

You can combine lookups with filters, tests and even each other to do some complex data generation and manipulation. For example:

tasks:
  - name: valid but useless and over complicated chained lookups and filters
    debug: msg="find the answer here:\n{{ lookup('url', 'https://google.com/search/?q=' + item|urlencode)|join(' ') }}"
    with_nested:
      - "{{ lookup('consul_kv', 'bcs/' + lookup('file', '/the/question') + ', host=localhost, port=2000')|shuffle }}"
      - "{{ lookup('sequence', 'end=42 start=2 step=2')|map('log', 4)|list) }}"
      - ['a', 'c', 'd', 'c']

You can control how errors behave in all lookup plugins by setting errors to ignore, warn, or strict. The default setting is strict, which causes the task to fail if the lookup returns an error. For example:

To ignore lookup errors:

- name: if this file does not exist, I do not care .. file plugin itself warns anyway ...
  debug: msg="{{ lookup('file', '/nosuchfile', errors='ignore') }}"

[WARNING]: Unable to find '/nosuchfile' in expected paths (use -vvvvv to see paths)

ok: [localhost] => {
    "msg": ""
}

To get a warning instead of a failure:

- name: if this file does not exist, let me know, but continue
  debug: msg="{{ lookup('file', '/nosuchfile', errors='warn') }}"

[WARNING]: Unable to find '/nosuchfile' in expected paths (use -vvvvv to see paths)

[WARNING]: An unhandled exception occurred while running the lookup plugin 'file'. Error was a <class 'ansible.errors.AnsibleError'>, original message: could not locate file in lookup: /nosuchfile

ok: [localhost] => {
    "msg": ""
}

To get a fatal error (the default):

- name: if this file does not exist, FAIL (this is the default)
  debug: msg="{{ lookup('file', '/nosuchfile', errors='strict') }}"

[WARNING]: Unable to find '/nosuchfile' in expected paths (use -vvvvv to see paths)

fatal: [localhost]: FAILED! => {"msg": "An unhandled exception occurred while running the lookup plugin 'file'. Error was a <class 'ansible.errors.AnsibleError'>, original message: could not locate file in lookup: /nosuchfile"}

Forcing lookups to return lists: query and wantlist=True

In Ansible 2.5, a new Jinja2 function called query was added for invoking lookup plugins. The difference between lookup and query is largely that query will always return a list. The default behavior of lookup is to return a string of comma separated values. lookup can be explicitly configured to return a list using wantlist=True.

This feature provides an easier and more consistent interface for interacting with the new loop keyword, while maintaining backwards compatibility with other uses of lookup.

The following examples are equivalent:

lookup('dict', dict_variable, wantlist=True)

query('dict', dict_variable)

As demonstrated above, the behavior of wantlist=True is implicit when using query.

Additionally, q was introduced as a shortform of query:

q('dict', dict_variable)

Plugin list

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