2021-08-17: Can't create Merge trains because of Reference not found error
Current Status
From 2021-08-16 23:43
to 2021-08-17 11:01
Merge trains were broken with the following error:
removed this merge request from the merge train because Reference not found
This error was only seen on projects where merge trains were enabled.
While it's common for GitLab inc. to use the merge trains feature, we didn't get many customer reports for it being broken. There were two tickets opened, 230954 and 230998.
Based on a db query of the notes table, ~400 projects were affected in total, around ~2000 MRs saw the error. We cannot easily determine the exact number of users affected.
Timeline
View recent production deployment and configuration events / gcp events (internal only)
All times UTC.
2021-08-16
-
23:43
- feature 'cache_merge_to_ref_calls' updated to 'true'
2021-08-17
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09:34
- @vshushlin declares incident in Slack. -
11:00
- @tkuah identifies gitlab-org/gitlab!67789 (merged) as a suspect recent feature flag. @engwan disables the feature flag. We appear to be recovering. -
11:01
- feature 'cache_merge_to_ref_calls' updated to 'false'
Corrective Actions
Corrective actions should be put here as soon as an incident is mitigated, ensure that all corrective actions mentioned in the notes below are included.
- We caught this issue in QA against prod with the full test suite, but it was not caught on staging. The feature flag skipped staging so maybe we need more guardrails to enforce setting feature flags there first. https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/980
- Should we move all feature flag enables to the
#production
channel? It might add more noise but it could help with awareness gitlab-com/chatops#112 (closed) - Did we know in advance whether merge trains might possibly be affected?
- Enforce feature flags on Staging, before Production gitlab-com/chatops#109 (closed)
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