[Feature flag] Rollout of `ci_child_pipeline_coverage_reports`

Summary

This issue is to rollout the feature on production, that is currently behind the ci_child_pipeline_coverage_reports feature flag.

Owners

Team: ~"group::pipeline insights"
Most `#g_pipeline_insights"
Best individual to reach out to: @alberts-gitlab
PM: @jocelynjane

Stakeholders

Expectations

What are we expecting to happen?

It enables the feature to include coverage reports from child pipelines into the MR coverage report.

When is the feature viable?

Feature flag ci_child_pipeline_coverage_reports is enabled.

What might happen if this goes wrong?

What can we monitor to detect problems with this?

Consider mentioning checks for 5xx errors or other anomalies like an increase in redirects (302 HTTP response status)

What can we check for monitoring production after rollouts?

https://dashboards.gitlab.net/d/000000167/postgresql-tuple-statistics?orgId=1&var-env=gprd&var-instance=patroni-v12-05-db-gprd.c.gitlab-production.internal&var-db=gitlabhq_production&var-top_dead_tup=All&from=now-3h&to=now

Database reads

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. The best environment to validate the feature in is staging-canary as this is the first environment deployed to. Note you will need to make sure you are configured to use canary as outlined here when accessing the staging environment in order to make sure you are testing appropriately.

Specific rollout on production

Ensure that the feature MRs have been deployed to both production and canary.
- /chatops run auto_deploy status <merge-commit-of-your-feature>
If you're using project-actor, you must enable the feature on these entries:
- /chatops run feature set --project=gitlab-org/gitlab,gitlab-org/gitlab-foss,gitlab-com/www-gitlab-com <feature-flag-name> true
If you're using group-actor, you must enable the feature on these entries:
- /chatops run feature set --group=gitlab-org,gitlab-com <feature-flag-name> true
If you're using user-actor, you must enable the feature on these entries:
- /chatops run feature set --user=<your-username> <feature-flag-name> true
Verify that the feature works on the specific entries. Posting the QA result in this issue is preferable.

Preparation before global rollout

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.
Ensure that any breaking changes have been announced following the release post process to ensure GitLab customers are aware.
Notify #support_gitlab-com and your team channel (more guidance when this is necessary in the dev docs).

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_TEAM_NAME).

(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:

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.

You can either create a follow-up issue for Feature Flag Cleanup or use the checklist below in this same issue.

Rollback Steps

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

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

Edited Oct 06, 2022 by Albert