[GSTG] Enable USE_REDIS_CACHE_STORE_AS_SESSION_STORE environment variable

Production Change

Change Summary

Enable USE_REDIS_CACHE_STORE_AS_SESSION_STORE environment variable for webservices which is going to change the format of sessions data in ServiceRedisSessions.

Related MR: gitlab-org/gitlab!176108 (merged)

Full context: gitlab-com/gl-infra/data-access/durability/team#35 (closed)

Change Details

1. Services Impacted - ServiceWeb ServiceRedisSessions

2. Change Technician - @marcogreg

3. Change Reviewer - @fshabir

4. Scheduled Date and Time (UTC in format YYYY-MM-DD HH:MM) - 2025-01-28 03:00

5. Time tracking - 30

6. 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 (mins) - 15 mins

• Set label changein-progress /label ~change::in-progress
• Prepare a session that is already logged in to staging.gitlab.com
• Merge MR to update env var USE_REDIS_CACHE_STORE_AS_SESSION_STORE in k8s gitlab-com/gl-infra/k8s-workloads/gitlab-com!4103 (merged)
• Refresh browser, ensure user is still logged in
• Try logging out and logging in again
• 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) - 15 mins

• Revert MR gitlab-com/gl-infra/k8s-workloads/gitlab-com!4103 (merged)
• Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

• Metric: Web apdex/error ratio
  • Location: https://dashboards.gitlab.net/d/web-main/web3a-overview?orgId=1&from=now-6h%2Fm&to=now%2Fm&timezone=utc&var-PROMETHEUS_DS=mimir-gitlab-gstg&var-environment=gstg&var-stage=main
  • What changes to this metric should prompt a rollback: Drop in apdex/increase in error ratio
• Metric: Auth related metrics
  • Location: https://dashboards.gitlab.net/d/JyaDfEWWz/user-authentication-events?orgId=1&from=now-6h&to=now&timezone=utc&var-env=gstg&var-environment=gstg&var-type=api&var-type=git&var-type=web&var-type=websockets&refresh=5m
  • What changes to this metric should prompt a rollback: Any anomalies in one of the metric

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. Mention @gitlab-org/saas-platforms/inframanagers in this issue to request approval and provide visibility to all infrastructure managers.
  • 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.