[GSTG] Configuring Gitlab Rails for sidekiq sharding

Production Change

Change Summary

The change configures Gitlab.com to be ready for a sharded Sidekiq setup. See scalability#3173 for overview on the plan.

This CR focuses on configuring k8s and chef nodes with the updated routing rules and new Redis configuration details.

Scheduled for 17 April 2024 0200h UTC

Change Details

1. Services Impacted - ServiceSidekiq ServiceRedisSidekiq
2. Change Technician - @schin1
3. Change Reviewer - @fshabir
4. Time tracking - 1h
5. Downtime Component - NA

Set Maintenance Mode in GitLab

If your change involves scheduled maintenance, add a step to set and unset maintenance mode per our runbooks. This will make sure SLA calculations adjust for the maintenance period.

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (60 mins)

• Set label changein-progress /label ~change::in-progress
• Add secrets for rails user into vault -- see https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/redis/provisioning-redis-cluster.md#3-configure-gitlab-rails for details
• Merge MR for k8s-workloads to set the Redis configurations
  • Create external secrets: gitlab-com/gl-infra/k8s-workloads/gitlab-com!3495 (merged)
  • Set Redis config: gitlab-com/gl-infra/k8s-workloads/gitlab-com!3496 (merged)
• Merge chef MR to configure deployer and console nodes. Note that password needs to be set now
  • redis config: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/4592 (MR contains instructions for setting password)
  • routing rule: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/4593
• Merge MR for k8s-workloads to updating routing rules: gitlab-com/gl-infra/k8s-workloads/gitlab-com!3509 (merged).
  • note that this CR is pending chart bump to receive the change in gitlab-org/charts/gitlab!3682 (merged)
• Merge MR for k8s-workloads to define a new shard: gitlab-com/gl-infra/k8s-workloads/gitlab-com!3510 (merged)
  • Verify that the redis-sidekiq-catchall-a instance starts receiving BRPOP commands using thanos chart
• Set label changecomplete /label ~change::complete

Rollback

Rollback steps - steps to be taken in the event of a need to rollback this change

Estimated Time to Complete (60 mins)

• Revert k8s-workload MR in the reverse order as required. i.e. if the new shard provisioned is breaking, revert that only.
• Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

Check queue size for dangling queues after 100% feature flag cutover.

• Metric: redis activity
  • Location: thanos
  • What changes to this metric should prompt a rollback: when the proportion of lpush and brpop does not match the feature flag toggle. e.g. if workload has moved to the new shard, we should see an increase in lpush on the catchall_a shard.

Change Reviewer checklist

C4 C3 C2 C1:

• Check if the following applies:
  • The scheduled day and time of execution of the change is appropriate.
  • The change plan is technically accurate.
  • The change plan includes estimated timing values based on previous testing.
  • The change plan includes a viable rollback plan.
  • The specified metrics/monitoring dashboards provide sufficient visibility for the change.

C2 C1:

• Check if the following applies:
  • The complexity of the plan is appropriate for the corresponding risk of the change. (i.e. the plan contains clear details).
  • The change plan includes success measures for all steps/milestones during the execution.
  • The change adequately minimizes risk within the environment/service.
  • The performance implications of executing the change are well-understood and documented.
  • The specified metrics/monitoring dashboards provide sufficient visibility for the change.
    • If not, is it possible (or necessary) to make changes to observability platforms for added visibility?
  • The change has a primary and secondary SRE with knowledge of the details available during the change window.
  • The change window has been agreed with Release Managers in advance of the change. If the change is planned for APAC hours, this issue has an agreed pre-change approval.
  • The labels blocks deployments and/or blocks feature-flags are applied as necessary.

Change Technician checklist

• Check if all items below are complete:
  • The change plan is technically accurate.
  • This Change Issue is linked to the appropriate Issue and/or Epic
  • Change has been tested in staging and results noted in a comment on this issue.
  • A dry-run has been conducted and results noted in a comment on this issue.
  • The change execution window respects the Production Change Lock periods.
  • For C1 and C2 change issues, the change event is added to the GitLab Production calendar.
  • For C1 and C2 change issues, the SRE on-call has been informed prior to change being rolled out. (In #production channel, mention @sre-oncall and this issue and await their acknowledgement.)
  • For C1 and C2 change issues, the SRE on-call provided approval with the eoc_approved label on the issue.
  • For C1 and C2 change issues, the Infrastructure Manager provided approval with the manager_approved label on the issue.
  • Release managers have been informed prior to any C1, C2, or blocks deployments change being rolled out. (In #production channel, mention @release-managers and this issue and await their acknowledgment.)
  • There are currently no active incidents that are severity1 or severity2
  • If the change involves doing maintenance on a database host, an appropriate silence targeting the host(s) should be added for the duration of the change.