Gitlab auto merge race condition

[michelmzs]

We experienced a behavior when the Gitlab option Pipelines must succeed is enabled and the Atlantis auto-merge option either. Sometimes the Atlantis PUT request for merging the MR returns 405 Method Not Allowed.

Analyzing the problem in our environment, apparently, the situation occurs because the auto-merge command on Atlantis does not check the mergeability status or the external pipeline status before executing.

Anyone else experienced that behavior?

Update:
We did a patch adding a sleep time before the automerge(), and until now the error rate dropped to below 2%.

[swade1987]

We have also been experiencing this since moving to 0.16 and also with our move to 0.17 as well (see below)

We have placed Atlantis into debug mode and only get the following output

{
    "level": "error",
    "ts": 1622712784.8012686,
    "caller": "events/automerger.go:37",
    "msg": "automerging failed: unable to merge merge request, it may not be in a mergeable state: PUT https://gitlab.com/api/v4/projects/redacted/tf-env-security-groups/merge_requests/39/merge: 405 {message: 405 Method Not Allowed}",
    "json": {
        "repo": "redacted/tf-env-security-groups",
        "pull": "39"
    },
    "stacktrace": "github.com/runatlantis/atlantis/server/events.(*AutoMerger).automerge\n\t/home/circleci/project/server/events/automerger.go:37\ngithub.com/runatlantis/atlantis/server/events.(*ApplyCommandRunner).Run\n\t/home/circleci/project/server/events/apply_command_runner.go:161\ngithub.com/runatlantis/atlantis/server/events.(*DefaultCommandRunner).RunCommentCommand\n\t/home/circleci/project/server/events/command_runner.go:212"
}

[devlucasc]

I did this fix here #1675