2023-09-20: rails_replica_sql Apdex SLO Violation
Customer Impact
Web requests may have been intermittently slower.
Current Status
DB apdex and web apdex is high at this time and are adding another DB replica. The root cause is lightweight lock contention, similar to #15987 (comment 1469159260). The same behavior is repeated on 2023-09-20 and 2023-09-21.
To resolve this issue we've added a new DB replica and have seen the apdex has stabilized.
In #16404 (comment 1573060066) we are discussing if there are other long-term fixes.
📝 Summary for CMOC notice / Exec summary:
- Customer Impact: Potential slowdown of requests
- Service Impact: ServiceWeb
- Impact Duration: 2023-09-20 8:00 UTC - 15:43 UTC (463 minutes), 2023-09-21 12:00 UTC - ...
- Root cause: Lightweight lock contention on replica nodes
📚 References and helpful links
Recent Events (available internally only):
- Feature Flag Log - Chatops to toggle Feature Flags Documentation
- Infrastructure Configurations
- GCP Events (e.g. host failure)
Deployment Guidance
- Deployments Log | Gitlab.com Latest Updates
- Reach out to Release Managers for S1/S2 incidents to discuss Rollbacks, Hot Patching or speeding up deployments. | Rollback Runbook | Hot Patch Runbook
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