## Summary Roll out [the feature](https://gitlab.com/gitlab-org/gitlab/-/work_items/630717) currently behind the `zoekt_prioritized_rollout_selection` feature flag. - DRI: @rkumar555 - Team Slack channel: `#<slack-channel-of-dri-team>` > [!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? - The flag changes namespace selection order in the Zoekt rollout: `Search::Zoekt::SelectionService`, run by `Search::Zoekt::RolloutWorker`, picks paid namespaces without replicas first on GitLab.com, then any namespace without replicas, before falling back to the existing mismatched-replicas scan. Off keeps the previous behavior exactly. - The two new selection queries are anti-joins over `zoekt_enabled_namespaces`. Each keeps a cursor in `Rails.cache` (`SelectionService#with_cursor`). The unbounded scan ran about 3.4 seconds cold on a production clone (~68k buffers). It runs once per query per 10-minute window. Other runs start at the cursor and read tens to hundreds of buffers. `RolloutWorker` loops roughly every 6 seconds, so watch database load and worker duration. - Selection only decides which namespaces get provisioned next; it does not delete or move any existing index or replica, so there is no data loss risk. - Watch `RolloutWorker` duration and job rate, the count of paid namespaces still waiting (`Search::Zoekt::EnabledNamespace.with_rollout_allowed.with_paid_subscription.without_replicas.count`), and pending indices per node (`Search::Zoekt::Index.pending.group(:zoekt_node_id).count`). - With `zoekt_prioritized_rollout_selection` on, step 3 is the only path that removes extra replicas, and it runs only when steps 1 and 2 leave room in the batch. While namespaces without replicas are waiting, namespaces with too many replicas keep them, which holds node storage. ## Events - [Exceptions with zoekt_prioritized_rollout_selection: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:%22zoekt_prioritized_rollout_selection:1%22'),columns:!(json.exception.class,json.exception.message,json.extra.workflow_id,json.meta.caller_id),sort:!(!(json.time,desc)))) - [Events with zoekt_prioritized_rollout_selection: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:%22zoekt_prioritized_rollout_selection: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 `#<slack-channel-of-dri-team>`. 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** The flag is checked with `Feature.enabled?(:zoekt_prioritized_rollout_selection, :instance)`, so it is instance-wide: there is no actor to target and no partial state between off and on. ``` /chatops gitlab run feature set zoekt_prioritized_rollout_selection true --dev --pre --staging --staging-ref ``` **Production** — instance-wide flag, so enable fully and watch the dashboards above (wait and watch, there is no percentage step): ``` /chatops gitlab run feature set zoekt_prioritized_rollout_selection true ``` Roll back with the command in the Rollback section if anything looks wrong. ## 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 - Check on a gprd read-only console that over-provisioned namespaces are near zero: ```ruby Search::Zoekt::EnabledNamespace.where.not(number_of_replicas_override: nil).count Search::Zoekt::Replica.group(:zoekt_enabled_namespace_id).having('COUNT(*) > 1').count.size ``` If either is not near zero, reserve a step-3 slot in `SelectionService` before enabling. Re-run this check if you set a `number_of_replicas_override` while the flag is on, because that namespace waits in step 3 behind namespaces without replicas. ## 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 https://gitlab.com/gitlab-org/gitlab/-/merge_requests/257853 19.5 /chatops gitlab run feature delete zoekt_prioritized_rollout_selection --dev --pre --staging --staging-ref --production ``` ## Rollback ``` /chatops gitlab run feature set zoekt_prioritized_rollout_selection false # production /chatops gitlab run feature set zoekt_prioritized_rollout_selection false --dev --pre --staging --staging-ref # non-production /chatops gitlab run feature delete zoekt_prioritized_rollout_selection --dev --pre --staging --staging-ref --production # remove entirely ```