2022-08-18: Reduce the default TTL for Rails.cache to 8 hours from 12 hours

Production Change

Change Summary

This will reduce the default TTL of Rails.cache from 12 hours to 8 hours

For scalability#1854

Follow up of #7604 (closed)

Change Details

1. Services Impacted - ServiceAPI ServiceWeb ServiceGit ServiceSidekiq ServiceRedis
2. Change Technician - @reprazent
3. Change Reviewer -
4. Time tracking -
5. Downtime Component - none

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - Estimated Time to Complete in Minutes

• Set label changein-progress /label ~change::in-progress
• [gprd] Merge gitlab-com/gl-infra/k8s-workloads/gitlab-com!2050 (merged)
• 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 (mins) - Estimated Time to Complete in Minutes

• Revert gitlab-com/gl-infra/k8s-workloads/gitlab-com!2050 (merged)
• Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

In staging it will take a long time for these changes to have any effect.

• Metric: Cache miss ratios in prometheus
  • Location: Prometheus gprd
  • Location Thanos
  • What changes to this metric should prompt a rollback: Too many cache misses
• Service dashboards for web/api/git/sidekiq

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.

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.
  • 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 (If needed! Cases include DB change) prior to 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.