Declare local file argument for module

Archives Ansible Developer
1

Hello list,

I was trying to make my first steps writing an Ansible module (in Python).
The main documentation is pretty clear, so i moved very smoothly using the AnsibleModule helper class.
So far, i have been using only simple arguments: scalars or JSON-serializable structs (lists, dicts etc.).

Now, i need to declare a file argument (say src given as a local path) that is present at Ansible’s control
host and must be transferred to the managed host (and then it will acquire a temporary file name).
This is very similar to what the copy module does: when the module is executed on the managed host
the src argument is just a remote temporary file path (and i assume transfer has already taken place).

I was looking into copy module’s source code (to mimic it and declare such an argument), but i was
not able to figure it out. Is there some kind of magic (control-side pre-execute hooks?) behind the behavior of
modules like copy and template ?

So, my question: does a custom module have the option to transfer a control-side file and handle it (managed-side)
as a normal file path? Or instead, must we break this into 2 tasks (one builtin copy task, one custom task)?

Thank you!

2

The copy module also uses an action plugin that runs on the controlling
machine to read/transfer the local file:

https://github.com/ansible/ansible/blob/devel/lib/ansible/runner/action_plugins/copy.py

3

Ok, I understand, so i suppose each module that needs some special control-side action needs to have a
corresponding action plugin.

The problem is that i cannot find any relevant documentation at http://docs.ansible.com/developing_plugins.html
for creating an action plugin (besides, of course, the source code itself).

Is this type of plugin is not supposed/encouraged to be developed outside of the core Ansible team?

4

Not discouraged, but normally not recommended until you've written
some independent modules first. We lack development docs for most
other plugin types, but they are not that hard to do.

5

Thanks Brian,

So, i suppose my alternatives are

  • prepend a copy task before each module invocation, or
  • replace an src argument with a contents argument filled with the contents of the control-side file (e.g. via lookup(“file”))