## Summary Roll out [caching the X-Total count across pages on `GET /groups/:id/merge_requests`](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/257173) currently behind the `cache_total_count_on_group_merge_requests_api` feature flag. - DRI: @marc_shaw - 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? With the flag on, `GET /groups/:id/merge_requests` caches the `X-Total` count in Redis for 15 minutes per user and filter set. Page 1 always runs the count. Pages after the first and before the last reuse the cached count instead of running it again, so `X-Total` can be up to 15 minutes stale on those pages. The page the cached count calls the last one always recounts, so `X-Next-Page` and the `Link` header stay correct when merge requests are created during a walk. Nothing is written to the database, and cached counts expire within 15 minutes of turning the flag off. To measure the effect, compare `json.db_duration_s` for this endpoint on requests with `page` greater than 1 before and after enabling it for a group. ## Events <!-- Replace feature flag name in the link--> - [Exceptions with cache_total_count_on_group_merge_requests_api: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:%22cache_total_count_on_group_merge_requests_api:1%22'),columns:!(json.exception.class,json.exception.message,json.extra.workflow_id,json.meta.caller_id),sort:!(!(json.time,desc)))) - [Events with cache_total_count_on_group_merge_requests_api: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:%22cache_total_count_on_group_merge_requests_api:1%22'),columns:!(json.meta.caller_id,json.feature_flag_states),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 cache_total_count_on_group_merge_requests_api 50 --actors --dev --pre --staging --staging-ref /chatops gitlab run feature set cache_total_count_on_group_merge_requests_api true --dev --pre --staging --staging-ref ``` **Production** - percentage rollout (wait ≥15 min between steps, watch dashboards): ``` /chatops gitlab run feature set cache_total_count_on_group_merge_requests_api <percentage> --actors ``` Or target specific actors instead: ``` /chatops gitlab run feature set --project=gitlab-org/gitlab,gitlab-org/gitlab-foss cache_total_count_on_group_merge_requests_api true /chatops gitlab run feature set --group=gitlab-org,gitlab-com cache_total_count_on_group_merge_requests_api true /chatops gitlab run feature set --user=marc_shaw cache_total_count_on_group_merge_requests_api 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/-/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 cache_total_count_on_group_merge_requests_api --dev --pre --staging --staging-ref --production ``` ## Rollback ``` /chatops gitlab run feature set cache_total_count_on_group_merge_requests_api false # production /chatops gitlab run feature set cache_total_count_on_group_merge_requests_api false --dev --pre --staging --staging-ref # non-production /chatops gitlab run feature delete cache_total_count_on_group_merge_requests_api --dev --pre --staging --staging-ref --production # remove entirely ``` <!-- /label ~"type::feature" ~"feature::addition" /label ~"type::maintenance" /label ~"type::bug" -->