[GPRD][PG16 Upgrade] - Test multi-slot PostgreSQL logical replication upgrade playbook with Production workload for 24 hours
Production Change
Change Summary
2nd attempt to perform this CR - #18049 (closed) (aborted)
Fixes were applied into the upgrade playbook - https://gitlab.com/gitlab-com/gl-infra/dbre/-/issues/61
Last year during the PG14 upgrade, we found that single slot logical replication couldn't handle our MAIN database workload due to single processing WAL decoding limitations.
This year we are planning to use multi-slot logical replication for the PG16 upgrade. For tha reasons, we require to perform a test of the upgrade
playbook with 4 slot logical replication and monitor it for 24 hours in the Production environment to observe if the multi-slot solution will handle the workload and what kind of data inconsistency and errors might happen in the standby cluster.
The idea of multi-slot logical replication is to allow us to antecipate the upgrade
from the switchover
as much as possible, which should reduce the maintenance window time and risks, and more important to have a longer period of rollback (ideally multiple days), hence reducing the risks in case of performance regression in the 16 version.
Note: with single-slot we could only allow a rollback period of a few hours;
Objectives
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Measure playbook steps timing with real production data -
Evaluate Multi-Slot logical replication for 24 hours (including a peak period) -
Analyze metrics and lagging; -
Analyze errors and data consistency issues;
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Change Details
- Services Impacted - ServicePatroni
- Change Technician - @rhenchen.gitlab
- Change Reviewer - @bshah11 @vitabaks
- Time tracking - 4 days
- Downtime Component - no downtime (database migrations need to be disabled for 24 hours)
PCL - Production Change Lock
As discussed at https://gitlab.slack.com/archives/CCFV016SV/p1716512591351799 we changed the CR execution window and we also need to define a Soft PCL to block "delivery" during the period
- MR Soft PCL during CR: TODO
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) - Estimated Time to Complete in Minutes
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Set label changein-progress /label ~change::in-progress
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Change Step 1 -
Change Step 2 -
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
-
Rollback Step 1 -
Rollback Step 2 -
Set label changeaborted /label ~change::aborted
Monitoring
Key metrics to observe
- Metric: Metric Name
- Location: Dashboard URL
- What changes to this metric should prompt a rollback: Describe Changes
Change Reviewer checklist
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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.
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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
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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.