Is it possible to use an Ansible Core Module within a Custom Module?

Question

There is also this related question "Access predefined ansible modules in custom module" but unfortunately without an helpful answer.

In general, I would like to create a Custom Module which uses some Core Modules.

If I e.g. want to use the Core Module file, I could of course look at the main function and extract the parts needed by importing the functions required.

So to create / remove a file this would require to use something like

from ansible.modules.file import check_owner_exists, check_group_exists, keep_backward_compatibility_on_timestamps, ensure_file_attributes, ensure_absent

Then copy the required code and use it accordingly.

This seems like a huge workaround for something as simple as importing a core module in a custom module.

Are there any better ways to call the file module in a custom module?

Answer 1

As @U880D already pointed out, it is not possible call a module from another module.

The way around this is to use an action plugin (https://docs.ansible.com/ansible/latest/dev_guide/developing_plugins.html#developing-actions. The most prominent example is probably the template module:

• https://github.com/ansible/ansible/blob/devel/lib/ansible/plugins/action/template.py which contains the actual code
• https://github.com/ansible/ansible/blob/devel/lib/ansible/modules/template.py which only contains the documentation

In the hope it simplifies life for others, here is what I ended up using.

So to run the file module inside our own "module" we create library/custom_file.py (the "module" file containing only the documentation) with content

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# Copyright: ...
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)

DOCUMENTATION = r"""
---
<...>
"""
EXAMPLES = r"""
---
<...>
"""
RETURN = r"""
---
<...>
"""

and action_plugins/custom_file.py with

#!/usr/bin/env python3

from ansible.plugins.action import ActionBase

class ActionModule(ActionBase):
    def run(self, tmp=None, task_vars=None):
        result = super(ActionModule, self).run(tmp, task_vars)

        result.update(self._execute_module(
            module_name="file", module_args=file_args, task_vars=task_vars, tmp=tmp
        ))

        return result

now we can use this "module" in our playbook test.yml

- name: Test my new module
  gather_facts: false
  hosts: localhost
  tasks:
    - name: Run custom file module
      custom_file:
        path: /etc/foo.conf
        owner: foo
        group: foo
        mode: '0644'

Answer 2

Regarding your assumption

... for something as simple as importing a Core Module in a Custom Module ...

you could review Developing 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 ansible or ansible-playbook programs.

which indicates (at least for me) that such was never intended and therefore isn't possible. The answer on "How to access predefined Ansible Modules in Custom Module" is helpful as it shows how to do it instead ...

Are there any better ways to call the file module in a Custom Module?

... and which is in your case to use the file module within a playbook.

Similar Q&A

• Calling an Ansible Module from another Ansible Module?

  You can't execute a module from within other module, because modules in Ansible are self-contained entities, that are packaged on the controller and delivered to remote host for execution.

---

What would indeed be possible is to import module_utils if there are any. See in example

• Importing Ansible module_utils
• How to import a .py file into an Ansible Module?