2022-08-19: [GSTG] Use turbo mode on restore command

Production Change

Change Summary

During the incident a replica fell behind the leader and when we needed to have it catch up, the WAL-G --turbo flag was required to speed up the restore of WAL (transaction log) files from the WAL-G GCS archive location as seen here. This change request seeks to add the --turbo flag to scripts that perform a wal-g wal-fetch or wal-g backup-fetch as this is not always common knowledge for the EOC. WAL-G's --turbo flag is available to "Ignore all kinds of throttling defined in config".

Change Details

1. Services Impacted - ServicePostgres
2. Change Technician - @anganga
3. Change Reviewer - @rhenchen.gitlab
4. Time tracking - 30 minutes
5. Downtime Component - none

Detailed steps for the change

Change Steps - steps to take to execute the change

Estimated Time to Complete (mins) - 30 minutes

• Set label changein-progress /label ~change::in-progress
• Merge the MR https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/2268
• Force Chef to run in all affected nodes:
  • for node in $(knife search 'roles:gstg-base-db-patroni-*' -i); do knife ssh "name:$node" -- 'sudo chef-client'; done
  • for node in $(knife search 'roles:gstg-base-db-postgres-replication' -i); do knife ssh "name:$node" -- 'sudo chef-client'; done
• 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) - 30 minutes

• Revert the MR https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/2268
• Force Chef to run in all affected nodes:
  • for node in $(knife search 'roles:gstg-base-db-patroni-*' -i); do knife ssh "name:$node" -- 'sudo chef-client'; done
  • for node in $(knife search 'roles:gstg-base-db-postgres-replication' -i); do knife ssh "name:$node" -- 'sudo chef-client'; done
• Set label changeaborted /label ~change::aborted

Monitoring

Key metrics to observe

GSTG

• Metric: PostgreSQL Replication Overview

  • Location: https://dashboards.gitlab.net/goto/eVRfuCmVz?orgId=1
  • What changes to this metric should prompt a rollback: If there is a drop in the number of replicas

• Check postgres and wal-g push logs to check for errors

  • Location: /var/log/gitlab/postgresql/postgresql.csv and /var/log/wal-g/wal-g.log
  • What changes should prompt a rollback: errors related with wal-g failing should be evaluated to check if they are related with the new option

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.