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Add documentation about info/facts module development (#71250)

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Fixes: #40151

Signed-off-by: Abhijeet Kasurde <akasurde@redhat.com>
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Abhijeet Kasurde 4 years ago committed by GitHub
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179
docs/docsite/rst/dev_guide/developing_modules_general.rst
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@ -5,7 +5,7 @@
Developing Ansible modules
**************************
A module is a reusable, standalone script that Ansible runs on your behalf, either locally or remotely. Modules interact with your local machine, an API, or a remote system to perform specific tasks like changing a database password or spinning up a cloud instance. Each module can be used by the Ansible API, or by the :command:`ansible` or :command:`ansible-playbook` programs. A module provides a defined interface, accepts arguments, and returns information to Ansible by printing a JSON string to stdout before exiting.
A module is a reusable, standalone script that Ansible runs on your behalf, either locally or remotely. Modules interact with your local machine, an API, or a remote system to perform specific tasks like changing a database password or spinning up a cloud instance. Each module can be used by the Ansible API, or by the :command:`ansible` or :command:`ansible-playbook` programs. A module provides a defined interface, accepts arguments, and returns information to Ansible by printing a JSON string to stdout before exiting.
If you need functionality that is not available in any of the thousands of Ansible modules found in collections, you can easily write your own custom module. When you write a module for local use, you can choose any programming language and follow your own rules. Use this topic to learn how to create an Ansible module in Python. After you create a module, you must add it locally to the appropriate directory so that Ansible can find and execute it. For details about adding a module locally, see :ref:`developing_locally`.
@ -48,145 +48,56 @@ Creating a development environment (platform-agnostic steps)
``$ . venv/bin/activate && . hacking/env-setup``
Creating an info or a facts module
==================================
Ansible gathers information about the target machines using facts modules, and gathers information on other objects or files using info modules.
If you find yourself trying to add ``state: info`` or ``state: list`` to an existing module, that is often a sign that a new dedicated ``_facts`` or ``_info`` module is needed.
In Ansible 2.8 and onwards, we have two type of information modules, they are ``*_info`` and ``*_facts``.
If a module is named ``<something>_facts``, it should be because its main purpose is returning ``ansible_facts``. Do not name modules that do not do this with ``_facts``.
Only use ``ansible_facts`` for information that is specific to the host machine, for example network interfaces and their configuration, which operating system and which programs are installed.
Modules that query/return general information (and not ``ansible_facts``) should be named ``_info``.
General information is non-host specific information, for example information on online/cloud services (you can access different accounts for the same online service from the same host), or information on VMs and containers accessible from the machine, or information on individual files or programs.
Info and facts modules, are just like any other Ansible Module, with a few minor requirements:
1. They MUST be named ``<something>_info`` or ``<something>_facts``, where <something> is singular.
2. Info ``*_info`` modules MUST return in the form of the :ref:`result dictionary<common_return_values>` so other modules can access them.
3. Fact ``*_facts`` modules MUST return in the ``ansible_facts`` field of the :ref:`result dictionary<common_return_values>` so other modules can access them.
4. They MUST support :ref:`check_mode <check_mode_dry>`.
5. They MUST NOT make any changes to the system.
6. They MUST document the :ref:`return fields<return_block>` and :ref:`examples<examples_block>`.
To create an info module:
1. Navigate to the correct directory for your new module: ``$ cd lib/ansible/modules/``. If you are developing module using collection, ``$ cd plugins/modules/`` inside your collection development tree.
2. Create your new module file: ``$ touch my_test_info.py``.
3. Paste the content below into your new info module file. It includes the :ref:`required Ansible format and documentation <developing_modules_documenting>` and some example code.
4. Modify and extend the code to do what you want your new info module to do. See the :ref:`programming tips <developing_modules_best_practices>` and :ref:`Python 3 compatibility <developing_python_3>` pages for pointers on writing clean and concise module code.
.. literalinclude:: ../../../../examples/scripts/my_test_info.py
:language: python
Use the same process to create a facts module.
.. literalinclude:: ../../../../examples/scripts/my_test_facts.py
:language: python
Creating a module
=================
To create a module:
1. Navigate to the correct directory for your new module: ``$ cd lib/ansible/modules/``
2. Create your new module file: ``$ touch my_test.py``
1. Navigate to the correct directory for your new module: ``$ cd lib/ansible/modules/``. If you are developing module using collection, ``$ cd plugins/modules/`` inside your collection development tree.
2. Create your new module file: ``$ touch my_test.py``.
3. Paste the content below into your new module file. It includes the :ref:`required Ansible format and documentation <developing_modules_documenting>` and some example code.
4. Modify and extend the code to do what you want your new module to do. See the :ref:`programming tips <developing_modules_best_practices>` and :ref:`Python 3 compatibility <developing_python_3>` pages for pointers on writing clean and concise module code.
.. code-block:: python
#!/usr/bin/python
# Copyright: (c) 2018, Terry Jones <terry.jones@example.org>
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
DOCUMENTATION = r'''
---
module: my_test
short_description: This is my test module
version_added: "2.4"
description:
- "This is my longer description explaining my test module."
options:
name:
description:
- This is the message to send to the test module.
required: true
type: str
new:
description:
- Control to demo if the result of this module is changed or not.
required: false
type: bool
extends_documentation_fragment:
- azure
author:
- Your Name (@yourhandle)
'''
EXAMPLES = r'''
# Pass in a message
- name: Test with a message
my_test:
name: hello world
# pass in a message and have changed true
- name: Test with a message and changed output
my_test:
name: hello world
new: true
# fail the module
- name: Test failure of the module
my_test:
name: fail me
'''
RETURN = r'''
original_message:
description: The original name param that was passed in
type: str
returned: always
message:
description: The output message that the test module generates
type: str
returned: always
'''
from ansible.module_utils.basic import AnsibleModule
def run_module():
# define available arguments/parameters a user can pass to the module
module_args = dict(
name=dict(type='str', required=True),
new=dict(type='bool', required=False, default=False)
)
# seed the result dict in the object
# we primarily care about changed and state
# changed is if this module effectively modified the target
# state will include any data that you want your module to pass back
# for consumption, for example, in a subsequent task
result = dict(
changed=False,
original_message='',
message=''
)
# the AnsibleModule object will be our abstraction working with Ansible
# this includes instantiation, a couple of common attr would be the
# args/params passed to the execution, as well as if the module
# supports check mode
module = AnsibleModule(
argument_spec=module_args,
supports_check_mode=True
)
# if the user is working with this module in only check mode we do not
# want to make any changes to the environment, just return the current
# state with no modifications
if module.check_mode:
module.exit_json(**result)
# manipulate or modify the state as needed (this is going to be the
# part where your module will do what it needs to do)
result['original_message'] = module.params['name']
result['message'] = 'goodbye'
# use whatever logic you need to determine whether or not this module
# made any modifications to your target
if module.params['new']:
result['changed'] = True
# during the execution of the module, if there is an exception or a
# conditional state that effectively causes a failure, run
# AnsibleModule.fail_json() to pass in the message and the result
if module.params['name'] == 'fail me':
module.fail_json(msg='You requested this to fail', **result)
# in the event of a successful module execution, you will want to
# simple AnsibleModule.exit_json(), passing the key/value results
module.exit_json(**result)
def main():
run_module()
if __name__ == '__main__':
main()
.. literalinclude:: ../../../../examples/scripts/my_test.py
:language: python
Verifying your module code
==========================
@ -259,7 +170,7 @@ You can run through Ansible's sanity checks in a container:
``$ ansible-test sanity -v --docker --python 2.7 MODULE_NAME``
.. note::
.. note::
Note that this example requires Docker to be installed and running. If you'd rather not use a container for this, you can choose to use ``--venv`` instead of ``--docker``.
Adding unit tests
@ -269,7 +180,7 @@ You can add unit tests for your module in ``./test/units/modules``. You must fir
- Install the requirements (outside of your virtual environment): ``$ pip3 install -r ./test/lib/ansible_test/_data/requirements/units.txt``
- Run ``. hacking/env-setup``
- To run all tests do the following: ``$ ansible-test units --python 3.5``. If you are using a CI enviornment, these tests will run automatically.
- To run all tests do the following: ``$ ansible-test units --python 3.5``. If you are using a CI environment, these tests will run automatically.
.. note:: Ansible uses pytest for unit testing.

134
examples/scripts/my_test.py
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@ -0,0 +1,134 @@
#!/usr/bin/env python
# Copyright: (c) 2018, Terry Jones <terry.jones@example.org>
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
DOCUMENTATION = r'''
---
module: my_test
short_description: This is my test module
# If this is part of a collection, you need to use semantic versioning,
# i.e. the version is of the form "2.5.0" and not "2.4".
version_added: "1.0.0"
description: This is my longer description explaining my test module.
options:
name:
description: This is the message to send to the test module.
required: true
type: str
new:
description:
- Control to demo if the result of this module is changed or not.
- Parameter description can be a list as well.
required: false
type: bool
# Specify this value according to your collection
# in format of namespace.collection.doc_fragment_name
extends_documentation_fragment:
- my_namespace.my_collection.my_doc_fragment_name
author:
- Your Name (@yourGitHubHandle)
'''
EXAMPLES = r'''
# Pass in a message
- name: Test with a message
my_namespace.my_collection.my_test:
name: hello world
# pass in a message and have changed true
- name: Test with a message and changed output
my_namespace.my_collection.my_test:
name: hello world
new: true
# fail the module
- name: Test failure of the module
my_namespace.my_collection.my_test:
name: fail me
'''
RETURN = r'''
# These are examples of possible return values, and in general should use other names for return values.
original_message:
description: The original name param that was passed in.
type: str
returned: always
sample: 'hello world'
message:
description: The output message that the test module generates.
type: str
returned: always
sample: 'goodbye'
'''
from ansible.module_utils.basic import AnsibleModule
def run_module():
# define available arguments/parameters a user can pass to the module
module_args = dict(
name=dict(type='str', required=True),
new=dict(type='bool', required=False, default=False)
)
# seed the result dict in the object
# we primarily care about changed and state
# changed is if this module effectively modified the target
# state will include any data that you want your module to pass back
# for consumption, for example, in a subsequent task
result = dict(
changed=False,
original_message='',
message=''
)
# the AnsibleModule object will be our abstraction working with Ansible
# this includes instantiation, a couple of common attr would be the
# args/params passed to the execution, as well as if the module
# supports check mode
module = AnsibleModule(
argument_spec=module_args,
supports_check_mode=True
)
# if the user is working with this module in only check mode we do not
# want to make any changes to the environment, just return the current
# state with no modifications
if module.check_mode:
module.exit_json(**result)
# manipulate or modify the state as needed (this is going to be the
# part where your module will do what it needs to do)
result['original_message'] = module.params['name']
result['message'] = 'goodbye'
# use whatever logic you need to determine whether or not this module
# made any modifications to your target
if module.params['new']:
result['changed'] = True
# during the execution of the module, if there is an exception or a
# conditional state that effectively causes a failure, run
# AnsibleModule.fail_json() to pass in the message and the result
if module.params['name'] == 'fail me':
module.fail_json(msg='You requested this to fail', **result)
# in the event of a successful module execution, you will want to
# simple AnsibleModule.exit_json(), passing the key/value results
module.exit_json(**result)
def main():
run_module()
if __name__ == '__main__':
main()

96
examples/scripts/my_test_facts.py
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@ -0,0 +1,96 @@
#!/usr/bin/env python
# Copyright: (c) 2020, Your Name <YourName@example.org>
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
DOCUMENTATION = r'''
---
module: my_test_facts
short_description: This is my test facts module
version_added: "1.0.0"
description: This is my longer description explaining my test facts module.
author:
- Your Name (@yourGitHubHandle)
'''
EXAMPLES = r'''
- name: Return ansible_facts
my_namespace.my_collection.my_test_facts:
'''
RETURN = r'''
# These are examples of possible return values, and in general should use other names for return values.
ansible_facts:
description: Facts to add to ansible_facts.
returned: always
type: dict
contains:
foo:
description: Foo facts about operating system.
type: str
returned: when operating system foo fact is present
sample: 'bar'
answer:
description:
- Answer facts about operating system.
- This description can be a list as well.
type: str
returned: when operating system answer fact is present
sample: '42'
'''
from ansible.module_utils.basic import AnsibleModule
def run_module():
# define available arguments/parameters a user can pass to the module
module_args = dict()
# seed the result dict in the object
# we primarily care about changed and state
# changed is if this module effectively modified the target
# state will include any data that you want your module to pass back
# for consumption, for example, in a subsequent task
result = dict(
changed=False,
ansible_facts=dict(),
)
# the AnsibleModule object will be our abstraction working with Ansible
# this includes instantiation, a couple of common attr would be the
# args/params passed to the execution, as well as if the module
# supports check mode
module = AnsibleModule(
argument_spec=module_args,
supports_check_mode=True
)
# if the user is working with this module in only check mode we do not
# want to make any changes to the environment, just return the current
# state with no modifications
if module.check_mode:
module.exit_json(**result)
# manipulate or modify the state as needed (this is going to be the
# part where your module will do what it needs to do)
result['ansible_facts'] = {
'foo': 'bar',
'answer': '42',
}
# in the event of a successful module execution, you will want to
# simple AnsibleModule.exit_json(), passing the key/value results
module.exit_json(**result)
def main():
run_module()
if __name__ == '__main__':
main()

111
examples/scripts/my_test_info.py
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@ -0,0 +1,111 @@
#!/usr/bin/env python
# Copyright: (c) 2020, Your Name <YourName@example.org>
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
DOCUMENTATION = r'''
---
module: my_test_info
short_description: This is my test info module
version_added: "1.0.0"
description: This is my longer description explaining my test info module.
options:
name:
description: This is the message to send to the test module.
required: true
type: str
author:
- Your Name (@yourGitHubHandle)
'''
EXAMPLES = r'''
# Pass in a message
- name: Test with a message
my_namespace.my_collection.my_test_info:
name: hello world
'''
RETURN = r'''
# These are examples of possible return values, and in general should use other names for return values.
original_message:
description: The original name param that was passed in.
type: str
returned: always
sample: 'hello world'
message:
description: The output message that the test module generates.
type: str
returned: always
sample: 'goodbye'
my_useful_info:
description: The dictionary containing information about your system.
type: dict
returned: always
sample: {
'foo': 'bar',
'answer': 42,
}
'''
from ansible.module_utils.basic import AnsibleModule
def run_module():
# define available arguments/parameters a user can pass to the module
module_args = dict(
name=dict(type='str', required=True),
)
# seed the result dict in the object
# we primarily care about changed and state
# changed is if this module effectively modified the target
# state will include any data that you want your module to pass back
# for consumption, for example, in a subsequent task
result = dict(
changed=False,
original_message='',
message='',
my_useful_info={},
)
# the AnsibleModule object will be our abstraction working with Ansible
# this includes instantiation, a couple of common attr would be the
# args/params passed to the execution, as well as if the module
# supports check mode
module = AnsibleModule(
argument_spec=module_args,
supports_check_mode=True
)
# if the user is working with this module in only check mode we do not
# want to make any changes to the environment, just return the current
# state with no modifications
if module.check_mode:
module.exit_json(**result)
# manipulate or modify the state as needed (this is going to be the
# part where your module will do what it needs to do)
result['original_message'] = module.params['name']
result['message'] = 'goodbye'
result['my_useful_info'] = {
'foo': 'bar',
'answer': 42,
}
# in the event of a successful module execution, you will want to
# simple AnsibleModule.exit_json(), passing the key/value results
module.exit_json(**result)
def main():
run_module()
if __name__ == '__main__':
main()

3
test/sanity/code-smell/package-data.py
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@ -54,6 +54,9 @@ def assemble_files_to_ship(complete_file_list):
'.mailmap',
# Possibly should be included
'examples/scripts/uptime.py',
'examples/scripts/my_test.py',
'examples/scripts/my_test_info.py',
'examples/scripts/my_test_facts.py',
'examples/DOCUMENTATION.yml',
'examples/play.yml',
'examples/hosts.yaml',

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