## Summary Roll out [the feature](https://gitlab.com/gitlab-org/gitlab/-/work_items/604785) currently behind the `unfold_diff_note_large_blob` feature flag. - DRI: @patrickbajao - Team Slack channel: `#g_code_review` > [!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? `unfold_diff_note_large_blob` gates `Gitlab::Diff::LinesUnfolder` counting lines from the raw blob data (byte scan, capped at the 1 MB viewable size) instead of `Gitlab::BlobHelper#lines`. - **Blast radius:** the unfolder is used both on diff-note creation (`DiffNote` line-code resolution) and at render time via `CollectionUnfolder` (expanding context around notes on every diff view). For files > 1 MB the render path was previously a no-op; with the flag on it parses up to 1 MB of blob data per unfolded file. - **No-op for the common case:** for files ≤ 1 MB the fetched blob data is already ≤ 512 KB, so the cap does not slice and behavior is unchanged. - **Dashboards to watch:** API `POST .../discussions` error rate (the 400s this fixes) and diff-rendering latency on https://dashboards.gitlab.net. ## 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 unfold_diff_note_large_blob 50 --actors --dev --pre --staging --staging-ref /chatops gitlab run feature set unfold_diff_note_large_blob true --dev --pre --staging --staging-ref ``` **Production** — percentage rollout (wait ≥15 min between steps, watch dashboards): ``` /chatops gitlab run feature set unfold_diff_note_large_blob <percentage> --actors ``` Or target specific actors instead: ``` /chatops gitlab run feature set --project=gitlab-org/gitlab,gitlab-org/gitlab-foss unfold_diff_note_large_blob true /chatops gitlab run feature set --group=gitlab-org,gitlab-com unfold_diff_note_large_blob true /chatops gitlab run feature set --user=patrickbajao unfold_diff_note_large_blob true ``` ## 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 - [Breaking changes](https://docs.gitlab.com/development/documentation/release_notes/#deprecations-removals-and-breaking-changes) announced, if any - [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 ## 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). Track it here, or open a follow-up [Feature Flag Cleanup issue](https://gitlab.com/gitlab-org/gitlab/-/issues/new?description_template=Feature%20Flag%20Cleanup). Remove the flag and its YAML definition from the codebase, then: ``` /chatops gitlab run release check https://gitlab.com/gitlab-org/gitlab/-/merge_requests/244076 <milestone> /chatops gitlab run feature delete unfold_diff_note_large_blob --dev --pre --staging --staging-ref --production ``` ## Rollback ``` /chatops gitlab run feature set unfold_diff_note_large_blob false # production /chatops gitlab run feature set unfold_diff_note_large_blob false --dev --pre --staging --staging-ref # non-production /chatops gitlab run feature delete unfold_diff_note_large_blob --dev --pre --staging --staging-ref --production # remove entirely ```