Support for container client other than podman?

[reubeno]

I'm looking at using mock's bootstrap image support, but one of the host OSes I need to support (Azure Linux 3.0) doesn't provide podman. Is there openness to supporting alternative container runtime clients like docker? At quick glance, it looks like most of the operations are translatable with somewhat different command line invocations. (image mount doesn't seem to have a direct counterpart, but that only seems to be used in a copy operation that perhaps we could simulate in another way.)

I'm happy to work toward this but wanted to check in here first to see what I might be missing and if there would be openness to add such support. I'm familiar with the architectural differences between podman and docker et al. (and the benefits of the former), and at the same time am trying to make things work 😄.

Looking through the code, I see almost all of the interactions with podman are abstracted through the Podman class in podman.py. There's just one notable exception, in mock-hermetic-repo.py:

mock/mock/py/mock-hermetic-repo.py

Lines 108 to 118 in 4cb091b

	pull_cmd = ["podman", "pull"]
	if "pull_digest" in bootstrap_data:
	image_specification += "@" + bootstrap_data["pull_digest"]
	if "architecture" in bootstrap_data:
	pull_cmd += ["--arch", bootstrap_data["architecture"]]
	pull_cmd += [image_specification]
	log.info("Pulling like: %s", ' '.join(pull_cmd))
	subprocess.check_output(pull_cmd)
	subprocess.check_output(["podman", "save", "--format=oci-archive", "--quiet",
	"-o", os.path.join(outputdir, "bootstrap.tar"),
	image_specification])

My thought is that we could:

• Add a new option (command line?) that permits selecting a different container runtime client, with options podman and docker (defaults to podman).
• Extract Podman class's existing interface to an abstract base class ContainerClient (or similar name); derive Podman class from it.
• Implement Docker class to implement ContainerClient.
• Replace calls to Podman() to a factory function that inspects config and dispatches appropriately to Podman() vs. Docker().
• Update the linked code in mock-hermetic-repo.py with calls through these classes.

Thanks in advance for any feedback on the above!

[xsuchy]

As you stated, there is no support for anything other than podman right now.
We are open to adding new features, but it will be up to you to create a PR and to support it - if something breaks in that part of the code, we will assign it to you.
We will happily review the PR and merge it after the review.