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2023-01-31: Functionally shard redis-repository-cache from redis-cache in production.

Production Change

Change Summary

Using feature flags, we will first dual write all redis-repository-cache keys to both redis-repository-cache and then redis-cache, and then we will transition to only using redis-cache. The process will take approximately 8 hours (due to TTLs) and will be done during the quiestest period possible, beginning at approximately 2100 UTC (pre-change steps) and completed by 0700 UTC.

scalability#2054 is the scalability issue.

gitlab-org/gitlab#388080 (closed) is the issue for the feature flags in question.

Change Details

  1. Services Impacted - ServiceRedis
  2. Change Technician - @stejacks-gitlab and @reprazent
  3. Change Reviewer - @msmiley
  4. Time tracking - 24h

Detailed steps for the change

Pre-change Steps

Estimated Time to Complete (mins) - 60 minutes

  • Update chef-repo vault with new password and key:
stejacks@atlas~/projects/gitlab-com/gl-infra/chef-repo (master) $ EDITOR=vim bin/gkms-vault-edit gitlab-omnibus-secrets gprd

"gitlab-rails": {
...
 "redis_repository_cache_instance": "redis://<IAMAPASSWORD>@gprd-redis-repository-cache",
...

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - 1440 minutes

$ sudo gitlab-redis-cli bgsave

# Monitor the file on disk, once it stops increasing in size, it's ready to be used!
$ sudo ls -lta /var/opt/gitlab/redis/dump.rdb

# Once the file is ready, move it to a safe-er location, for example
$ sudo mv /var/opt/gitlab/redis/dump.rdb /var/opt/gitlab/redis/dump-8309.rdb

Rollback

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

Estimated Time to Complete (mins) - 30 minutes.

  • Turn all feature flags to false:
/chatops run feature set use_primary_and_secondary_stores_for_repository_cache false
/chatops run feature set use_primary_store_as_default_for_repository_cache false

Monitoring

Key metrics to observe

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 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 (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.
Edited by Stephanie Jackson
OSZAR »