Export prometheus metric for read-only mode

Exports a Prometheus metrics showing whether a virtual storage is in read-only mode or not.

Relates to #2789 (closed)

changed milestone to %13.1

added Category:Gitaly Observability backstage [DEPRECATED] devopscreate groupgitaly + 1 deleted label

changed title from export prometheus metric for read-only mode to Export prometheus metric for read-only mode

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assigned to @samihiltunen and unassigned @pks-t

@samihiltunen One nit, otherwise this looks fine to me. You should probably assign a second reviewer, though.

approved this merge request

assigned to @pks-t and @johncai

unassigned @pks-t

resolved all threads

would we want to put this in updateMetrics ?

@johncai I'll leave this as it is. This is where the value originates from so it is the most up to date value. I considered moving this to updateMetrics but it requires more changes without a clear gain. The metrics being separate gauges, it is still possible for the primary gauge to be inconsistent with read-only mode gauge even if moved in to updateMetrics. This could be fixed by the approach in #2809 (closed) but I'll leave it for later until the proposal is accepted.

changed this line in version 2 of the diff

approved this merge request

@samihiltunen some nits only, not blocking so I'll pre-approve

unassigned @johncai

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• 0d5e6b09 - export prometheus metric for read-only mode

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merged

mentioned in commit 5c49063c