[Feature flag] Finalize ci_runner_separation_by_plan and enable ci_queuing_include_allowed_plans

Summary

This issue is to roll out the Runner separation by plan on production, that is currently behind the ci_runner_separation_by_plan and ci_queuing_include_allowed_plans feature flag.

Be aware that ci_runner_separation_by_plan exists since March 2022. That feature was an experiment and in review and the rollout to the production environment was finished. We need however to remove the feature flag itself 🙂 As the new MR changes a little how the whole mechanism worked, we're going to keep the feature flag in place until we finish the verification here and then we will remove both flags at the same time.

Owners

  • Most appropriate Slack channel to reach out to: #g_runner_saas
  • Best individual to reach out to: @tmaczukin

Expectations

What are we expecting to happen?

We will make the Runner Separation by plan feature fully working without disrupting the service and without negative impact on DB queries when reaching /api/v4/jobs/request API endpoint.

What can go wrong and how would we detect it?

As the change in !121761 (merged) is touching DB queries, this may affect the query that is used for scheduling CI/CD jobs to Runners. That can be observed and analyzed at https://dashboards.gitlab.net/d/ci-runners-incident-database/ci-runners3a-incident-support3a-database?from=now-3h%2Fm&to=now%2Fm&var-PROMETHEUS_DS=PA258B30F88C30650&var-environment=gprd&var-stage=main&var-shard=saas-linux-xlarge-amd64&var-runner_job_failure_reason=All&orgId=1.

We also know that when the feature doesn't work as expected (which is the whole point behind !121761 (merged)) it may cause some of the jobs to get stuck in the pending state. This was described in some more details at #412915 (closed).

Rollout Steps

Rollout on non-production environments

  • Verify the MR with the feature flag is merged to master and have been deployed to non-production environments with /chatops run auto_deploy status https://gitlab.com/gitlab-org/gitlab/-/merge_requests/121761

  • Enable the feature globally on non-production environments with

    • /chatops run feature set ci_queuing_include_allowed_plans true --staging --staging-ref
    • /chatops run feature set ci_runner_separation_by_plan true --staging --staging-ref (this is to make sure that the existing feature flag is still enabled)

  • Verify that the feature works as expected. The best environment to validate the feature in is staging-canary as this is the first environment deployed to. Make sure you are configured to use canary.

  • If the feature flag causes end-to-end tests to fail, disable the feature flag on staging to avoid blocking deployments.

For assistance with end-to-end test failures, please reach out via the #quality Slack channel. Note that end-to-end test failures on staging-ref don't block deployments.

Specific rollout on production

For visibility, all /chatops commands that target production should be executed in the #production Slack channel and cross-posted (with the command results) to the responsible team's Slack channel (#g_runner_saas).

  • Ensure that the feature MRs have been deployed to both production and canary with /chatops run auto_deploy status https://gitlab.com/gitlab-org/gitlab/-/merge_requests/121761
Not applicable as these are instance-wide feature flags
  • Depending on the type of actor you are using, pick one of these options:
    • For project-actor: /chatops run feature set --project=gitlab-org/gitlab,gitlab-org/gitlab-foss,gitlab-com/www-gitlab-com <feature-flag-name> true
    • For group-actor: /chatops run feature set --group=gitlab-org,gitlab-com <feature-flag-name> true
    • For user-actor: /chatops run feature set --user=<your-username> <feature-flag-name> true
  • Verify that the feature works for the specific actors.

Preparation before global rollout

  • 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. YES, IT DOES 👉 gitlab-com/gl-infra/production#18459 (closed)

  • 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.

  • Ensure that documentation exists for the feature, and the version history text has been updated. (not applicable)

  • Leave a comment on the feature issue announcing estimated time when this feature flag will be enabled on GitLab.com.

  • Ensure that any breaking changes have been announced following the release post process to ensure GitLab customers are aware. (not applicable)

  • Notify the #support_gitlab-com Slack channel and your team channel (more guidance when this is necessary in the dev docs).

  • Ensure that the feature flag rollout plan is reviewed by another developer familiar with the domain.

Global rollout on production

For visibility, all /chatops commands that target production should be executed in the #production Slack channel and cross-posted (with the command results) to the responsible team's Slack channel (#g_runner_saas).

  • (Optional) Incrementally roll out the feature on production environment. (not applicable as it's an instance-wide feature flag)

    • Between every step wait for at least 15 minutes and monitor the appropriate graphs on https://dashboards.gitlab.net.
    • Perform actor-based rollout: /chatops run feature set <feature-flag-name> <rollout-percentage> --actors

  • Enable the feature globally on production environment:

    • /chatops run feature set ci_queuing_include_allowed_plans true
    • /chatops run feature set ci_runner_separation_by_plan true (this is to make sure that the existing feature flag is still enabled)

  • Observe appropriate graphs on https://dashboards.gitlab.net and verify that services are not affected.

  • Leave a comment on the feature issue announcing that the feature has been globally enabled.

  • Wait for at least one day for the verification term.

(Optional) Release the feature with the feature flag

WARNING: This approach has the downside that it makes it difficult for us to clean up the flag. For example, on-premise users could disable the feature on their GitLab instance. But when you remove the flag at some point, they suddenly see the feature as enabled and they can't roll it back to the previous behavior. To avoid this potential breaking change, use this approach only for urgent matters.

See instructions if you're sure about enabling the feature globally through the feature flag definition

If you're still unsure whether the feature is deemed stable but want to release it in the current milestone, you can change the default state of the feature flag to be enabled. To do so, follow these steps:

  • Create a merge request with the following changes. Ask for review and merge it.
  • Ensure that the default-enabling MR has been included in the release package. If the merge request was deployed before the monthly release was tagged, the feature can be officially announced in a release blog post: /chatops run release check <merge-request-url> <milestone>
  • Consider cleaning up the feature flag from all environments by running these chatops command in #production channel. Otherwise these settings may override the default enabled: /chatops run feature delete <feature-flag-name> --dev --staging --staging-ref --production
  • Close the feature issue to indicate the feature will be released in the current milestone.
  • Set the next milestone to this rollout issue for scheduling the flag removal.
  • (Optional) You can create a separate issue for scheduling the steps below to Release the feature.
    • Set the title to "[Feature flag] Cleanup <feature-flag-name>".
    • Execute the /copy_metadata <this-rollout-issue-link> quick action to copy the labels from this rollout issue.
    • Link this rollout issue as a related issue.
    • Close this rollout issue.

Release the feature

After the feature has been deemed stable, the clean 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 or use the checklist below in this same issue.

  • Create a merge request to remove the ci_queuing_include_allowed_plans and ci_runner_separation_by_plan feature flag.s 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.
    • Create a changelog entry.

  • Ensure that the cleanup MR has been included in the release package. If the merge request was deployed before the monthly release was tagged, the feature can be officially announced in a release blog post: /chatops run release check <merge-request-url> <milestone> (not applicable)

  • Close the feature issue to indicate the feature will be released in the current milestone.

  • Confirm that the MR was deployed to GitLab.com

  • Clean up the feature flag from all environments by running these chatops command in #production channel:

    • /chatops run feature delete ci_queuing_include_allowed_plans --pre --staging --staging-ref --production
    • /chatops run feature delete ci_runner_separation_by_plan --pre --staging --staging-ref --production

  • Close this rollout issue.

Rollback Steps

  • This feature can be disabled by running the following Chatops command:
/chatops run feature set ci_queuing_include_allowed_plans false
/chatops run feature set ci_runner_separation_by_plan false
Edited by Tomasz Maczukin