[Feature flag] Enable billable_member_async_deletion

Summary

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

Owners

Most appropriate Slack channel to reach out to: #g_utilization
Best individual to reach out to: @vij

Expectations

What are we expecting to happen?

Async billable user deletion will insert a row into the Members::DeletionSchedule table (members_deletion_schedules). This is controlled via the FF billable_member_async_deletion (code)
Members::PruneDeletionsWorker: this is a limited capacity worker that is scheduled every 5th minute to check for any Members::DeletionSchedule records and remove the user. This worker is enabled via the FF limited_capacity_member_destruction and is already enabled on production (this rollout issue, code). Only one worker should ever run at a time, and each instance of the worker will process at most:
- 10 scheduled deletions
- 100 member records per scheduled deletion
- and is limited to a 60s execution time.

What can go wrong and how would we detect it?

Based on a previous incident tangentially related to this work, we can primarily monitor CPU utilization for the patroni primary (link below)

We can use these charts for monitoring:

PG Primary CPU Grafana dashboard - https://dashboards.gitlab.net/goto/taxt1XOHR?orgId=1
Redis/Sidekiq Grafana dashboard - https://dashboards.gitlab.net/goto/7yyc1uOHR?orgId=1
Kibana workers/deletions dashboard - https://log.gprd.gitlab.net/app/r/s/2LkeD

We have successfully tested this process with a particularly large namespace hierarchy, #501060 (comment 2270063969).

We can safely disable this and the corresponding limited_capacity_member_destruction FFs if necessary.

Disabling limited_capacity_member_destruction will mean:

any existing Members::DeletionSchedule DB records will stop being processed by the limited capacity worker
users associated to those records won't have been (fully) removed

Disabling billable_member_async_deletion will mean we will stop adding to the Members::DeletionSchedule table, and go back to synchronous removal.

Any un-removed users will still show as members within the group's billable member page, so the group owners can initiate the removal again (but this will fallback to the previous behaviour of removing them synchronously)

Re-enabling the FFs will simply mean those DB records will be processed (and new ones will be added when customers choose to remove billable members)

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 has 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 billable_member_async_deletion <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 billable_member_async_deletion 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.
- See #e2e-run-staging Slack channel and look for the following messages:
  - test kicked off: Feature flag billable_member_async_deletion has been set to true on **gstg**
  - test result: This pipeline was triggered due to toggling of billable_member_async_deletion feature flag

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 must 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 billable_member_async_deletion true
- For group-actor: /chatops run feature set --group=gitlab-org,gitlab-com billable_member_async_deletion true
- For user-actor: /chatops run feature set --user=vij billable_member_async_deletion true
- For all internal users: /chatops run feature set --feature-group=gitlab_team_members billable_member_async_deletion 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.
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).

Global rollout on production

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

Incrementally roll out the feature on production.
- Example: /chatops run feature set billable_member_async_deletion <rollout-percentage> --actors.
- Between every step wait for at least 15 minutes and monitor the appropriate graphs on https://dashboards.gitlab.net.
After the feature has been 100% enabled, wait for at least one day before releasing the feature.

(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 billable_member_async_deletion 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.
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 https://gitlab.com/gitlab-org/gitlab/-/merge_requests/172505 17.6
Close [the feature issue][#501249 (closed)] to indicate the feature will be released in the current milestone.
Once the cleanup MR has been deployed to production, clean up the feature flag from all environments by running these chatops command in #production channel: /chatops run feature delete billable_member_async_deletion --dev --pre --staging --staging-ref --production
Close this rollout issue.

Rollback Steps

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

/chatops run feature set billable_member_async_deletion false

Disable the feature flag on non-production environments:

/chatops run feature set billable_member_async_deletion false --dev --pre --staging --staging-ref

Delete feature flag from all environments:

/chatops run feature delete billable_member_async_deletion --dev --pre --staging --staging-ref --production

Edited Jan 30, 2025 by Vijay Hawoldar