## Summary Roll out [the feature](https://gitlab.com/gitlab-org/gitlab/-/work_items/628194) currently behind the `restore_missing_mr_diff_commits` feature flag. - DRI: @marc_shaw - Team Slack channel: `#g_code_review` Introduced by https://gitlab.com/gitlab-org/gitlab/-/merge_requests/256346. Actor: project. > [!note] > Process and guidance live in the docs - this issue is just the commands and a place to track the rollout. > "Rolling out" means incrementally enabling the flag on GitLab.com to validate stability - it is not the same as releasing the feature, which happens when the flag is removed. > [Feature flag controls](https://docs.gitlab.com/development/feature_flags/controls/) · [Feature flag lifecycle](https://handbook.gitlab.com/handbook/product-development/how-we-work/product-development-flow/feature-flag-lifecycle/#feature-flag-lifecycle) ## What could go wrong? When a merge request diff has `commits_count > 0` but no rows in `merge_request_diff_commits`, a read enqueues `MergeRequests::RestoreDiffCommitsWorker`, which copies the diff's rows back from `merge_request_diff_commits_archived` with `ON CONFLICT DO NOTHING`. - Writes only rows that already exist in the archived table for that diff, so the worst case is a no-op job, not bad data. - Diffs whose archived rows are legacy shape (no metadata pointer, over 1000 versions) re-enqueue a no-op job on every read while the flag is on. Watch the `merge_requests_restore_diff_commits` queue for repeated jobs with `inserted_rows: 0`. - The worker is deferred on `merge_request_diff_commits` health signals and deduplicated per diff. - Enabling the flag before the console `reload_diff` script runs makes that script skip MRs the worker has already fixed. Dashboards: [Sidekiq queue detail](https://dashboards.gitlab.net/d/sidekiq-queue-detail/sidekiq-queue-detail?var-queue=merge_requests_restore_diff_commits) and the Kibana links below. ## Events - [Exceptions with restore_missing_mr_diff_commits:1](https://log.gprd.gitlab.net/app/discover#/?_g=(time:(from:now-1d,to:now))&_a=(index:'7092c4e2-4eb5-46f2-8305-a7da2edad090',query:(language:kuery,query:'json.exception.feature_flag_states.keyword:%22restore_missing_mr_diff_commits:1%22'),columns:!(json.exception.class,json.exception.message,json.extra.workflow_id,json.meta.caller_id),sort:!(!(json.time,desc)))) - [Events with restore_missing_mr_diff_commits:1](https://log.gprd.gitlab.net/app/discover#/?_g=(time:(from:now-1d,to:now))&_a=(index:'7092c4e2-4eb5-46f2-8305-a7da2edad090',query:(language:kuery,query:'json.feature_flag_states:%22restore_missing_mr_diff_commits:1%22'),columns:!(json.meta.caller_id,json.feature_flag_states),sort:!(!(json.time,desc)))) - [Worker runs](https://log.gprd.gitlab.net/app/discover#/?_g=(time:(from:now-1d,to:now))&_a=(index:'AWNABDRwNDuQHTm2tH6l',query:(language:kuery,query:'json.class:%22MergeRequests::RestoreDiffCommitsWorker%22'),columns:!(json.meta.project,json.merge_request_diff_id,json.commits_count,json.inserted_rows,json.duration_s),sort:!(!(json.time,desc)))) - [Error rate and other graphs by modifying the examples in the Visualization Library](https://log.gprd.gitlab.net/app/visualize#/?_g=h@358d019&s=FF%20Observability) Feature Flag events are only logged by default for feature flags marked for the current or future milestones. To enable while the feature flag is active, see https://docs.gitlab.com/development/feature_flags/#logging ## Rollout Run all production `/chatops` in [`#production`](https://gitlab.slack.com/archives/C101F3796) and cross-post the results to `#g_code_review`. Background: [incremental rollout process](https://docs.gitlab.com/development/feature_flags/controls/#process), [feature actors](https://docs.gitlab.com/development/feature_flags/#feature-actors). **Non-production** ``` /chatops gitlab run feature set restore_missing_mr_diff_commits 50 --actors --dev --pre --staging --staging-ref /chatops gitlab run feature set restore_missing_mr_diff_commits true --dev --pre --staging --staging-ref ``` **Production** - start with the affected customer project, then a test project, then percentage: ``` /chatops gitlab run feature set --project=marc_shaw/test restore_missing_mr_diff_commits true /chatops gitlab run feature set --project=<affected-customer-project> restore_missing_mr_diff_commits true /chatops gitlab run feature set restore_missing_mr_diff_commits <percentage> --actors ``` ## Before global rollout Confirm the relevant gotchas before going to 100% - see [enabling a feature for GitLab.com](https://docs.gitlab.com/development/feature_flags/controls/#enabling-a-feature-for-gitlabcom): - [Docs + version history](https://docs.gitlab.com/development/documentation/feature_flags/) updated - not applicable, internal repair path - [Breaking changes](https://docs.gitlab.com/development/documentation/release_notes/#deprecations-removals-and-breaking-changes) announced, if any - none - [Change management issue](https://handbook.gitlab.com/handbook/engineering/infrastructure-platforms/change-management/#feature-flags-and-the-change-management-process) opened, if required - [External API consumers](https://docs.gitlab.com/development/feature_flags/#do-not-use-feature-flags-in-external-api-consumers) handled with a fail-open mechanism, if applicable - not applicable ## Cleanup Remove the flag once [deemed stable](https://handbook.gitlab.com/handbook/product-development/how-we-work/product-development-flow/feature-flag-lifecycle/#feature-flag-lifecycle) - see [cleaning up](https://docs.gitlab.com/development/feature_flags/controls/#cleaning-up). Once the backfill in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/255692 has finished, the whole worker and its read-path hooks can be removed along with the flag. Track it here, or open a follow-up [Feature Flag Cleanup issue](https://gitlab.com/gitlab-org/gitlab/-/work_items/new?description_template=Feature%20Flag%20Cleanup). Remove the flag and its YAML definition from the codebase, then: ``` /chatops gitlab run release check <merge-request-url> <milestone> /chatops gitlab run feature delete restore_missing_mr_diff_commits --dev --pre --staging --staging-ref --production ``` ## Rollback ``` /chatops gitlab run feature set restore_missing_mr_diff_commits false # production /chatops gitlab run feature set restore_missing_mr_diff_commits false --dev --pre --staging --staging-ref # non-production /chatops gitlab run feature delete restore_missing_mr_diff_commits --dev --pre --staging --staging-ref --production # remove entirely ```