[Feature flag] Enable `zentao_issues_integration`

Summary

This issue is to rollout Integration with Zentao on production, that is currently behind the zentao_issues_integration feature flag.

Owners

• Team: ~"group::integrations"
• Most appropriate slack channel to reach out to: #g_ecosystem_integrations
• Best individual to reach out to: @.luke (GitLab.com assisting @icbd from JH)
• PM: @lpeng1991

Stakeholders

The Rollout Plan

1. Partial Rollout on GitLab.com with testing groups
2. Monitor Sentry for errors
3. Monitor Kibana and Prometheus latency for all actions of Projects::Integrations::ZentaoIssuesController
4. Rollout Feature for everyone

Testing Groups/Projects/Users

• https://gitlab.com/icbd-trial/integration-trial project
• https://gitlab.com/icbd-trial groups
• https://gitlab.com/.luke/public-tests project

Expectations

What are we expecting to happen?

The feature should be enabled with no negative effects to services.

What might happen if this goes wrong?

A very limited effect of high latency / errors affecting only the projects we enable for, and visible only when viewing ZenTao issues through the integration.

What can we monitor to detect problems with this?

See Rollout plan above

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 zentao_issues_integration true --dev
  • /chatops run feature set zentao_issues_integration 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).
• If the feature flag in code has an actor, enable it on GitLab.com for testing groups/projects.
  • /chatops run feature set --<actor-type>=<actor> zentao_issues_integration true
• Verify that the feature works as expected. Posting the QA result in this issue is preferable.

Global rollout on production

• Incrementally roll out the feature.
  • If the feature flag in code has an actor, perform actor-based rollout.
    • /chatops run feature set zentao_issues_integration <rollout-percentage> --actors
  • If the feature flag in code does NOT have an actor, perform time-based rollout (random rollout).
    • /chatops run feature set zentao_issues_integration <rollout-percentage>
  • Enable the feature globally on production environment.
    • /chatops run feature set zentao_issues_integration 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 zentao_issues_integration".
  • 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 zentao_issues_integration 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:
  • (Note because the feature flag name is the same as a licensed feature, I believe instead of the commands below, instead we will need someone with write access to staging and production to run: Feature.remove(:zentao_issues_integration)
  • [-] /chatops run feature delete zentao_issues_integration --dev
  • [-] /chatops run feature delete zentao_issues_integration --staging
  • [-] /chatops run feature delete zentao_issues_integration``
• Close this rollout issue.

Rollback Steps

Because the feature flag name is the same as a licensed feature, we need to ask someone with write access to production (like a SRE) to run Feature.disable(:zentao_issues_integration)