[Feature flag] Enable linear_group_including_descendants_by

Summary

Enable the :linear_group_including_descendants_by feature flag ...

Owners

• Team: Access
• Most appropriate slack channel to reach out to: #g_manage_access
• Best individual to reach out to: @fjsanpedro

Expectations

Faster group/namespace related queries.

What are we expecting to happen?

• No visible change
• Faster database performance, specifically with Namespace#self_and_descendants calls and all dependent code paths.
• Faster controller performance

What might happen if this goes wrong?

• Incorrect hierarchy data retrieved
• Incorrect hierarchy data recorded
• Internal server errors
• Unknown change in database load

What can we monitor to detect problems with this?

Potential deadlock and timeout logs:

• https://log.gprd.gitlab.net/goto/b2fdadb2687c423fb2b3743e39c590b7
• https://log.gprd.gitlab.net/goto/5473931fd2b87aac8f905cf1b1c5c48f?
• https://log.gprd.gitlab.net/goto/fbf7369dd143127165dc5f3da9809580

Web error rate https://dashboards.gitlab.net/d/web-main/web-overview?orgId=1

PostgreSQL activity https://dashboards.gitlab.net/d/000000144/postgresql-overview?orgId=1

Beta groups/projects

If applicable, any groups/projects that are happy to have this feature turned on early. Some organizations may wish to test big changes they are interested in with a small subset of users ahead of time for example.

• gitlab-org/gitlab-com groups
• ...

Rollout Steps

Rollout on non-production environments

• Ensure that the feature MRs have been deployed to non-production environments.
  • /chatops run auto_deploy status <merge-commit-of-your-feature>
• Enable the feature globally on non-production environments.
  • /chatops run feature set <feature-flag-name> true --dev
  • /chatops run feature set <feature-flag-name> true --staging
• Verify that the feature works as expected. Posting the QA result in this issue is preferable.

Preparation before production rollout

• Ensure that the feature MRs have been deployed to both production and canary.
  • /chatops run auto_deploy status <merge-commit-of-your-feature>
• Check if the feature flag change needs to be accompanied with a change management issue. 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.
• Ensure that documentation has been updated (More info).
• Announce on the feature issue an estimated time this will be enabled on GitLab.com.
• If the feature might impact the user experience, notify #support_gitlab-com and your team channel (more guidance when this is necessary in the dev docs).

Global rollout on production

All /chatops commands that target production should be done in the #production slack channel for visibility.

• Confirm the feature flag is enabled on staging without incident

• Roll out the feature to targeted testing projects/groups first

  • /chatops run feature set --project=gitlab-org/gitlab <feature-flag-name> true
  • /chatops run feature set --project=gitlab-org/gitlab-foss <feature-flag-name> true
  • /chatops run feature set --project=gitlab-com/www-gitlab-com <feature-flag-name> true

• Incrementally roll out the feature.

  • If the feature flag in code has an actor, perform actor-based rollout.
    • /chatops run feature set <feature-flag-name> <rollout-percentage> --actors
  • If the feature flag in code does NOT have an actor, perform time-based rollout (random rollout).
    • /chatops run feature set <feature-flag-name> <rollout-percentage>

• Verify the change has the desired outcome with the limited rollout before enabling the feature globally on production.

• Enable the feature globally on production environment. /chatops run feature set <feature-flag-name> true

• Announce on the feature issue 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

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.
  • Set the default_enabled attribute in the feature flag definition to true.
  • Create a changelog entry.
• Ensure that the default-enabling MR has been deployed to both production and canary. If the merge request was deployed before the code cutoff, the feature can be officially announced in a release blog post.
  • /chatops run auto_deploy status <merge-commit-of-default-enabling-mr>
• 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.

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.

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.

• Create a merge request to remove <feature-flag-name> feature flag. Ask for review and merge it.
  • 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 deployed to both production and canary. If the merge request was deployed before the code cutoff, the feature can be officially announced in a release blog post.
  • /chatops run auto_deploy status <merge-commit-of-cleanup-mr>
• Close the feature issue to indicate the feature will be released in the current milestone.
• Clean up the feature flag from all environments by running these chatops command in #production channel:
  • /chatops run feature delete <feature-flag-name> --dev
  • /chatops run feature delete <feature-flag-name> --staging
  • /chatops run feature delete <feature-flag-name>
• Close this rollout issue.

Rollback Steps

• This feature can be disabled by running the following Chatops command:

/chatops run feature set <feature-flag-name> false