[Feature flag] Rollout of `gitlab_for_slack_app_instance_and_group_level`

Summary

This issue is to roll out the feature on production, that is currently behind the gitlab_for_slack_app_instance_and_group_level feature flag.

Owners

Most appropriate Slack channel to reach out to: #g_manage_import_and_integrate
Best individual to reach out to: @bmarjanovic (and optionally @.luke after 26 March)

Expectations

What are we expecting to happen?

What can go wrong and how would we detect it?

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 have been deployed to non-production environments with /chatops run auto_deploy status <merge-commit-of-your-feature>

Deploy the feature flag at a percentage (recommended percentage: 50%) with /chatops run feature set gitlab_for_slack_app_instance_and_group_level <rollout-percentage> --actors --dev --pre --staging --staging-ref
Monitor that the error rates did not increase (repeat with a different percentage as necessary).

Enable the feature globally on non-production environments with /chatops run feature set gitlab_for_slack_app_instance_and_group_level true --dev --pre --staging --staging-ref
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 #test-platform 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.

Ensure that the feature MRs have been deployed to both production and canary with /chatops run auto_deploy status <merge-commit-of-your-feature>
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 gitlab_for_slack_app_instance_and_group_level true
- For group-actor: /chatops run feature set --group=gitlab-org,gitlab-com gitlab_for_slack_app_instance_and_group_level true
- For user-actor: /chatops run feature set --user=.luke gitlab_for_slack_app_instance_and_group_level 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. 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 exists for the feature, and the version history text has been updated.
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.
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

(Optional) Incrementally roll out the feature on production environment.
- 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 gitlab_for_slack_app_instance_and_group_level <rollout-percentage> --actors
Enable the feature globally on production environment: /chatops run feature set gitlab_for_slack_app_instance_and_group_level true
Observe appropriate graphs on https://dashboards.gitlab.net and verify that services are not affected.
Leave a comment on [the feature issue][main-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:

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 gitlab_for_slack_app_instance_and_group_level 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.
- 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> 16.8
Close [the feature issue][main-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 gitlab_for_slack_app_instance_and_group_level --dev --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 gitlab_for_slack_app_instance_and_group_level false

Edited Mar 28, 2024 by Bojan Marjanovic