docker_* modules: stop returning ansible_facts

[felixfontein]

SUMMARY

Some of the docker_* modules returned ansible_facts:

• docker_container returns a fact called docker_container;
• docker_network returns a fact called docker_network;
• docker_volume returns a fact called docker_volume;
• docker_service/docker_compose returns one fact named as the service for each service.

While this can be handy when using these modules, it is in general annoying for multiple reasons:

1. the modules pollute the variables namespace (especially the values they return are not host specific, since there might be more than one container/network/volume/... per host);
2. when trying to access the data of a registered result, one needs to write result.ansible_facts.docker_container when one cannot directly use the docker_container fact (for example, when using docker_container to start several containers in a loop);
3. in particular the way docker_compose returns facts named according to user input, it can easily happen that random variables are overridden, which is in most cases not what the user expects;
4. I don't think it was really intended to use facts in this way. Not really a reason, but I think many will agree... :-)

I've already created a PR (merged) which also returns the facts as regular return values, so people can start getting rid of the facts in their playbooks (#51192). I don't think this is enough, though. I want to deprecate the returned facts.

I know that in the past, return values of modules have been deprecated; see The ``win_disk_image`` module has deprecated the return value ``mount_path``, use ``mount_paths[0]`` instead. This will be removed in Ansible 2.11. in the 2.7 porting guide. I guess this hasn't been done for returned facts so far (they have been renamed in the past, though: the facts returned by docker_container have been renamed from ansible_docker_container to docker_container for Ansible 2.3 to avoid conflicts with the connection plugin.) Similarly to returned variables, it is not possible to warn the user when they are used, so that return values and returned facts should be deprecated with care. But I think that for the facts returned by these modules, it is really warranted to deprecate them!

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

docker_container
docker_network
docker_volume
docker_compose

[ansibot]

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[WojciechowskiPiotr]

Is the intention to remove returning any facts at all from those modules or you still want to return facts on the object that has been created/modified?

[felixfontein]

There is no point of returning facts of something which is not host-specific. So: no facts should be returned. (Regular return values should be used, no ansible_facts.)

[felixfontein]

Discussed at public ansible meeting today, logs are here. Motion to do this passed (last item on this meeting).

[jamescassell]

shipit

[felixfontein]

@WojciechowskiPiotr @jamescassell @gundalow and all others involved, thanks a lot for your feedback and helping to get this merged! :)