## Summary This issue is to roll out [the feature](https://gitlab.com/gitlab-org/gitlab/-/work_items/592720) on production, that is currently behind the `ci_finished_builds_ch_sync_mode_split` feature flag. When enabled during backfill, it splits 5 sync workers into 2 "recent" workers (processing records from the last 7 days) and 3 "backfill" workers (processing older records), ensuring newer build data reaches ClickHouse faster. ## Owners - Most appropriate Slack channel to reach out to: `#g_ci-platform` - Best individual to reach out to: @narendran-kannan ## Expectations ### What are we expecting to happen? - Recent builds (last 7 days) will be synced to ClickHouse with lower latency, as 2 dedicated workers process only recent records using `ORDER BY build_finished_at ASC, build_id ASC` with the new index - Backfill workers (3) continue processing older historical records independently - Overall throughput remains the same (5 total workers), but newer data is prioritized ### What can go wrong and how would we detect it? - Sync lag could increase if the mode split causes workers to process fewer records overall. Monitor the ClickHouse sync lag dashboard. - The new `order_by_build_finished_at` keyset ordering could have unexpected behavior with the in-operator optimization. Detect via increased error rates on `ClickHouse::CiFinishedBuildsSyncWorker`. - If backfill workers fall behind, the backfill migration completion could be delayed. Monitor `p_ci_finished_build_ch_sync_events` table size. ## Prerequisites - [x] Index MR merged and deployed: !226067 - [x] Verify index `index_ci_finished_build_ch_sync_events_on_mode_filter` exists in production - [x] Code MR merged and deployed: !226068 ## Rollout Steps Note: Please make sure to run the chatops commands in the Slack channel that gets impacted by the command. ### Rollout on non-production environments - Verify the MR with the feature flag is merged to `master` and has been deployed to non-production environments with `/chatops run auto_deploy status <merge-commit-of-your-feature>` - [x] Enable the feature globally on non-production environments with `/chatops run feature set ci_finished_builds_ch_sync_mode_split true --dev --pre --staging --staging-ref` - [x] Verify that the feature works as expected. The best environment to validate the feature in is [`staging-canary`](https://about.gitlab.com/handbook/engineering/infrastructure/environments/#staging-canary) as this is the first environment deployed to. Make sure you are [configured to use canary](https://next.gitlab.com/). - [ ] If the feature flag causes end-to-end tests to fail, disable the feature flag on staging to avoid blocking [deployments](https://about.gitlab.com/handbook/engineering/deployments-and-releases/deployments/). - See [`#e2e-run-staging` Slack channel](https://gitlab.enterprise.slack.com/archives/CBS3YKMGD) and look for the following messages: - test kicked off: `Feature flag ci_finished_builds_ch_sync_mode_split has been set to true on **gstg**` - test result: `This pipeline was triggered due to toggling of ci_finished_builds_ch_sync_mode_split feature flag` If you encounter end-to-end test failures and are unable to diagnose them, you may reach out to the [`#s_developer_experience` Slack channel](https://gitlab.enterprise.slack.com/archives/C07TWBRER7H) for assistance. Note that end-to-end test failures on `staging-ref` [don't block deployments](https://about.gitlab.com/handbook/engineering/infrastructure/environments/staging-ref/#how-to-use-staging-ref). ### Before production rollout - [ ] If the change is significant and you wanted to announce in [#whats-happening-at-gitlab](https://gitlab.enterprise.slack.com/archives/C0259241C), it best to do it before rollout to `gitlab-org/gitlab-com`. ### Specific rollout on production For visibility, all `/chatops` commands that target production must be executed in the [`#production` Slack channel](https://gitlab.slack.com/archives/C101F3796) and cross-posted (with the command results) to the responsible team's Slack channel. - Ensure that the feature MRs have been deployed to both production and canary with `/chatops run auto_deploy status <merge-commit-of-your-feature>` - [ ] Enable for all internal users: `/chatops run feature set --feature-group=gitlab_team_members ci_finished_builds_ch_sync_mode_split true` - [ ] Verify that the feature works for the specific actors. ### Preparation before global rollout - [x] Set a milestone to this rollout issue to signal for enabling and removing the feature flag when it is stable. - [ ] Check if the feature flag change needs to be accompanied with a [change management issue](https://about.gitlab.com/handbook/engineering/infrastructure-platforms/change-management/#feature-flags-and-the-change-management-process). Cross link the issue here if it does. - [ ] Ensure that you or a representative in development can be available for at least 2 hours after feature flag updates in production. If a different developer will be covering, or an exception is needed, please inform the oncall SRE by using the `@sre-oncall` Slack alias. - [ ] Notify the [`#support_gitlab-com` Slack channel](https://gitlab.slack.com/archives/C4XFU81LG) and your team channel ([more guidance when this is necessary in the dev docs](https://docs.gitlab.com/development/feature_flags/controls/#communicate-the-change)). ### Global rollout on production For visibility, all `/chatops` commands that target production must be executed in the [`#production` Slack channel](https://gitlab.slack.com/archives/C101F3796) and cross-posted (with the command results) to the responsible team's Slack channel. - [ ] [Incrementally roll out](https://docs.gitlab.com/development/feature_flags/controls/#process) the feature on production. - `/chatops run feature set ci_finished_builds_ch_sync_mode_split 50 --actors` - Between every step wait for at least 15 minutes and monitor the appropriate graphs on https://dashboards.gitlab.net. - [x] `/chatops run feature set ci_finished_builds_ch_sync_mode_split 100 --actors` - [x] After the feature has been 100% enabled, wait for [at least one day before releasing the feature](#release-the-feature). ### Release the feature After the feature has been [deemed stable](https://about.gitlab.com/handbook/product-development-flow/feature-flag-lifecycle/#including-a-feature-behind-feature-flag-in-the-final-release), the [clean up](https://docs.gitlab.com/development/feature_flags/controls/#cleaning-up) should be done as soon as possible to permanently enable the feature and reduce complexity in the codebase. You can either [create a follow-up issue for Feature Flag Cleanup](https://gitlab.com/gitlab-org/gitlab/-/issues/new?issuable_template=Feature%20Flag%20Cleanup) or use the checklist below in this same issue. - [x] Create a merge request to remove the `ci_finished_builds_ch_sync_mode_split` feature flag. Ask for review/approval/merge as usual. The MR should include the following changes: - Remove all references to the feature flag from the codebase. - Remove the YAML definitions for the feature from the repository. - [x] Ensure that the cleanup MR has been included in the release package. If the merge request was deployed before [the monthly release was tagged](https://about.gitlab.com/handbook/engineering/releases/#self-managed-releases-1), the feature can be officially announced in a release blog post: `/chatops run release check <merge-request-url> <milestone>` - [x] Close [the feature issue](https://gitlab.com/gitlab-org/gitlab/-/work_items/592720) to indicate the feature will be released in the current milestone. - [x] Once the cleanup MR has been deployed to production, clean up the feature flag from all environments by running these chatops command in `#production` channel: `/chatops run feature delete ci_finished_builds_ch_sync_mode_split --dev --pre --staging --staging-ref --production` - [x] Close this rollout issue. ## Rollback Steps - [ ] This feature can be disabled on production by running the following Chatops command: ``` /chatops run feature set ci_finished_builds_ch_sync_mode_split false ``` - [ ] Disable the feature flag on non-production environments: ``` /chatops run feature set ci_finished_builds_ch_sync_mode_split false --dev --pre --staging --staging-ref ``` - [ ] Delete feature flag from all environments: ``` /chatops run feature delete ci_finished_builds_ch_sync_mode_split --dev --pre --staging --staging-ref --production ``` ## Related - Feature issue: https://gitlab.com/gitlab-org/gitlab/-/work_items/592720 - Index MR: !226067 - Code MR: !226068