Officially deprecate "rails"

[tianon]

Given what it is (just a framework), and looking through https://github.com/search?l=dockerfile&q=%22FROM+rails%22&type=Code, I think it's time we finally cut the cord.

[yosifkit]

Rails itself is included in the Gemfile of a project that uses rails so that most users might even be installing a different version of rails than the one included in rails:latest. It is still useful for the first initialization of a rails project. We could help ease users over to the ruby image if we install the apt packages required for most rails installations (https://github.com/docker-library/rails/blob/db9122c0525e0a9f76ed47dbfb26e8e25ca0af70/Dockerfile#L7).

[yosifkit]

Maybe we should give a leniency period rather than this abrupt end. How about an EOL of maybe 6 months from now?

[tianon]

Yeah, I was planning on doing so, but calling it out explicitly and giving it a specific EOL date probably makes sense. 👍

[tianon]

Yeah, I suppose it is somewhat useful for initializing a new project... So perhaps we just deprecate the onbuild version of it? Even initializing a new project is pretty hacky, and requires funky bind-mount stuff, so I'm still neutral leaning towards -1 on keeping the image around just for that.

As for the deps, they're not actually universally required, so I think the fact that this text explicitly calls out "for a project using PostgreSQL" is probably good enough -- folks should be able to figure out that if they use MySQL, they need to include whatever their bindings need for that to work... 😄 (but maybe those client bindings make some sense in buildpack-deps to a certain extent?)

[tianon]

I've replaced:

... and will receive no further updates.

with:

and will receive no further updates after 2016-12-31 (Dec 31, 2016).

Happy to bikeshed on a different date, but I figured setting it somewhere in the far future should give a plenty big window for existing users (if we merge soon, that's over half a year / 6 months). It seems a little long, but I didn't think this discussion was quite open and shut yet so it can serve as a concrete point to discuss around. 😄

[yosifkit]

LGTM

[yosifkit]

I though about the possibility of adding the sql clients from the rails image to buildpack-deps so that all language stacks can use them. On buildpack-deps:jessie it is about 45MB to add them:

$ docker images buildpack-deps
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
buildpack-deps      temp                031a9584969b        5 seconds ago       655.4 MB
buildpack-deps      latest              f9f7b5cfe736        10 days ago         610 MB