ansible/docs/docsite/rst/plugins/vars.rst
Toshio Kuratomi 46b1a999c6
Collections docs generation backport (#70515)
* Build documentation for Ansible-2.10 (formerly known as ACD).

Builds plugin docs from collections whose source is on galaxy

The new command downloads collections from galaxy, then finds the
plugins inside of them to get the documentation for those plugins.

* Update the python syntax checks
  * docs builds can now require python 3.6+.

* Move plugin formatter code out to an external tool, antsibull-docs.
  Collection owners want to be able to extract docs for their own
  websites as well.
* The jinja2 filters, tests, and other support code have moved to antsibull
* Remove document_plugins as that has now been integrated into antsibull-docs

* Cleanup and bugfix to other build script code:
  * The Commands class needed to have its metaclass set for abstractmethod
    to work correctly
  * Fix lint issues in some command plugins

* Add the docs/docsite/rst/collections to .gitignore as
  everything in that directory will be generated so we don't want any of
  it saved in the git repository
* gitignore the build dir and remove edit docs link on module pages

* Add docs/rst/collections as a directory to remove on make clean
* Split the collections docs from the main docs

* remove version and edit on github
* remove version banner for just collections
* clarify examples need collection keyword defined

* Remove references to plugin documentation locations that no longer exist.
  * Perhaps the pages in plugins/*.rst should be deprecated
    altogether and their content moved?
  * If not, perhaps we want to rephrase and link into the collection
    documentation?
  * Or perhaps we want to link to the plugins which are present in
    collections/ansible/builtin?

* Remove PYTHONPATH from the build-ansible calls
  One of the design goals of the build-ansible.py script was for it to
  automatically set its library path to include the checkout of ansible
  and the library of code to implement itself.  Because it automatically
  includes the checkout of ansible, we don't need to set PYTHONPATH in
  the Makefile any longer.

* Create a command to only build ansible-base plugin docs
  * When building docs for devel, only build the ansible-base docs for
    now.  This is because antsibull needs support for building a "devel
    tree" of docs.  This can be changed once that is implemented
  * When building docs for the sanity tests, only build the ansible-base
    plugin docs for now.  Those are the docs which are in this repo so
    that seems appropriate for now.

* Docs: User guide overhaul, part 5 (#70307)

(cherry picked from commit db354c0300)

* Need to return any error code from running antsibull-docs (#70763)

This way we fail early if there's a problem

(cherry picked from commit 1e3989c9f7)

Co-authored-by: Alicia Cozine <879121+acozine@users.noreply.github.com>
2020-07-20 14:28:35 -07:00

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.. _vars_plugins:
Vars Plugins
============
.. contents::
:local:
:depth: 2
Vars plugins inject additional variable data into Ansible runs that did not come from an inventory source, playbook, or command line. Playbook constructs like 'host_vars' and 'group_vars' work using vars plugins.
Vars plugins were partially implemented in Ansible 2.0 and rewritten to be fully implemented starting with Ansible 2.4.
The :ref:`host_group_vars <host_group_vars_vars>` plugin shipped with Ansible enables reading variables from :ref:`host_variables` and :ref:`group_variables`.
.. _enable_vars:
Enabling vars plugins
---------------------
You can activate a custom vars plugin by either dropping it into a ``vars_plugins`` directory adjacent to your play, inside a role, or by putting it in one of the directory sources configured in :ref:`ansible.cfg <ansible_configuration_settings>`.
Starting in Ansible 2.10, vars plugins can require whitelisting rather than running by default. To enable a plugin that requires whitelisting set ``vars_plugins_enabled`` in the ``defaults`` section of :ref:`ansible.cfg <ansible_configuration_settings>` or set the ``ANSIBLE_VARS_ENABLED`` environment variable to the list of vars plugins you want to execute. By default, the :ref:`host_group_vars <host_group_vars_vars>` plugin shipped with Ansible is whitelisted.
Starting in Ansible 2.10, you can use vars plugins in collections. All vars plugins in collections require whitelisting and need to use the fully qualified collection name in the format ``namespace.collection_name.vars_plugin_name``.
.. code-block:: yaml
[defaults]
vars_plugins_enabled = host_group_vars,namespace.collection_name.vars_plugin_name
.. _using_vars:
Using vars plugins
------------------
By default, vars plugins are used on demand automatically after they are enabled.
Starting in Ansible 2.10, vars plugins can be made to run at specific times. `ansible-inventory` does not use these settings, and always loads vars plugins.
The global setting ``RUN_VARS_PLUGINS`` can be set in ``ansible.cfg`` using ``run_vars_plugins`` in the ``defaults`` section or by the ``ANSIBLE_RUN_VARS_PLUGINS`` environment variable. The default option, ``demand``, runs any enabled vars plugins relative to inventory sources whenever variables are demanded by tasks. You can use the option ``start`` to run any enabled vars plugins relative to inventory sources after importing that inventory source instead.
You can also control vars plugin execution on a per-plugin basis for vars plugins that support the ``stage`` option. To run the :ref:`host_group_vars <host_group_vars_vars>` plugin after importing inventory you can add the following to :ref:`ansible.cfg <ansible_configuration_settings>`:
.. code-block:: ini
[vars_host_group_vars]
stage = inventory
.. _vars_plugin_list:
Plugin Lists
------------
You can use ``ansible-doc -t vars -l`` to see the list of available plugins.
Use ``ansible-doc -t vars <plugin name>`` to see specific plugin-specific documentation and examples.
.. seealso::
:ref:`action_plugins`
Ansible Action plugins
:ref:`cache_plugins`
Ansible Cache plugins
:ref:`callback_plugins`
Ansible callback plugins
:ref:`connection_plugins`
Ansible connection plugins
:ref:`inventory_plugins`
Ansible inventory plugins
:ref:`shell_plugins`
Ansible Shell plugins
:ref:`strategy_plugins`
Ansible Strategy plugins
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