[WIP] lxc_container: replace subprocess.Popen() with run_command()

[russoz]

SUMMARY

The module was using subprocess.Popen() to run an external command, whilst the recommended way is to use AnsibleModule.run_command().

ISSUE TYPE

• Refactoring Pull Request

COMPONENT NAME

lxc_container

[ansibullbot]

cc @cloudnull
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[felixfontein]

I'm not sure this makes sense anymore. I think the temporary files are created so that if something goes wrong while executing the external command, that you can look at the temporary files to figure out what's happening. Like if the program doesn't terminate, takes too long, crashes - as the files arent' deleted.

Now stdout/stderr is only written after the program is done, and right afterwards the temporary files are deleted.

If we really want to use AnsibleModule.run_command here, we shouldn't create these files. But I'm not sure I understand this function good enough to be able to say whether Popen isn't better here...

@cloudnull, do you remember what's going on here?

[russoz]

create_script is called using lxc.Container.attach_wait(), which basically is a fork() that also changes the "container" where the process runs. The only temporary file that is deleted is the script_file one, and I agree it might be a good candidate for removal, but I did not want to change things too much in this PR.

[russoz]

Another thing I am not sure of: it is not clear how lxc.Container.attach_wait() handles the parameters for the called function. In its spec I saw *args, suggesting we can pass as many params we want. OTOH, every single example I saw calls attach_wait(func, [param1, param2]), suggesting that we should pass only one list/tuple with the params in it.

This part of the current code was from AI, and even though I did some spelunking in lxc code, at the end of the day that package is mostly bindings for C code. I am not confident of how the rules work in that case.

[russoz]

I will write the changelog fragment after the code change is settled.

[russoz]

friendly ping @cloudnull sorry to bother, any chance you could help with this? TIA