GitLab release pipeline: Centos7 image is missing

[chreekat]

Describe the bug

GitLab release pipelines are failing because the Centos7 image is missing.

https://gitlab.haskell.org/haskell/cabal/-/jobs?statuses=FAILED

Example job error:

https://gitlab.haskell.org/haskell/cabal/-/jobs/2122154

ERROR: Job failed: failed to pull image
"registry.gitlab.haskell.org/ghc/ci-images/x86_64-linux-centos7:a9297a370025101b479cfd4977f8f910814e03ab"
with specified policies [always]: Error response from daemon: manifest for
registry.gitlab.haskell.org/ghc/ci-images/x86_64-linux-centos7:a9297a370025101b479cfd4977f8f910814e03ab
not found: manifest unknown: manifest unknown (manager.go:251:0s)

Additional context

@bgamari had been cleaning up images and this image may have been considered "unused", though Ben will need to confirm.

Short term resolution

Ben said he would kick off a rebuild of this image so that it will continue to be available.

Long term resolution

Ben has proposed a new versioning scheme for ci images at https://gitlab.haskell.org/ghc/ci-images/-/issues/10 .

As long as Cabal's release pipeline is on GitLab so that it can share resources and build environments with GHC, changes to ci-images should take Cabal's use into account. Maybe now is a good time to provide some feedback.

[chreekat]

Should centos7 just be dropped? I don't know what cabal's cutoff is for supporting unsupported OSs is.

It's still failing as of today: https://gitlab.haskell.org/haskell/cabal/-/jobs/2127493

[ulysses4ever]

dropping CentOS 7 sound plausible to me

[chreekat]

Yeah, we need to drop it, and I'll do that.

Does Cabal have any place where policies are documented? I'd like to propose something to take the guesswork out of changes to the supported platforms for the release pipeline, but I don't know where to put it.

[chreekat]

I've figured out it's possible to keep centos7, so I'll prepare a patch that can be backported to current releases.

Whether to support it going forward is a different question.

[Bodigrim]

GHC itself dropped CentOS 7 in https://gitlab.haskell.org/ghc/ghc/-/commit/313cf27132a4da311adea2bc4c986aa423234431