GitLab v1 API compliance check returning 200 OK when metadata DB is disabled
Problem
While investigating gitlab#378731 (comment 1147959679) with @10io, we realized that the compliance check operation of the new GitLab V1 API in the registry always returns a 200 OK
response, even if the metadata DB (which is a strict requirement for the operation of all endpoints in this new API) is not enabled.
As result, GitLab Rails will attempt to use the new API to e.g. list tags (essential for most UI/API/background actions) for all recent repositories on self-managed instances (this is a separate problem, for which @10io will raise an issue). As expected, this will cause an exception, and all requests will fail because the metadata DB is not enabled.
Solution
Return 404 Not Found
when the metadata DB is not enabled. Update the documentation accordingly and release to all self-managed installs ASAP.
Workaround
While the fix is not released, the only option is to downgrade the GitLab Container Registry to version 3.20.0 (when the new API did not exist yet).