Geo: Adding a secondary node may slow down the primary node
Problem to solve
As can happen from time to time, depending on usage and infrastructure, a GitLab instance can get a little slow.
Add a Geo secondary. This adds load to the original instance. Even if we avoid streaming DB replication, the secondary will begin backfilling, which adds a constant amount of load, up to the concurrency settings.
For small instances, the default concurrency settings can easily be too high. I believe at least one customer adding Geo suffered from this problem making their original instance unusable for a time.
Intended users
Further details
Proposal
- Set default concurrency settings to the lowest common denominator, appropriate for 1k ref arch
- Add a final step to Geo setup docs: "Tune concurrency settings". Link to Tuning Geo.
- Open follow up to improve/expand details in Tuning Geo.