2021-06-06: SLO alerts all across gprd
Current Status
It appears there was an increase in errors across GitLab.com related to the loss of a read replica in our main data store. This loss of the replica was intentional as part of maintenance on that read replica, however the increase in error rate was unexpected. This seems to be unexpected behavior of traffic being routed to a read replica that was intentionally drained and removed from the cluster. We will pause the ongoing work related to the cluster until we learn the cause of this behavior.
Summary for CMOC notice / Exec summary:
- Customer Impact: Users of GitLab.com saw an increase in 500 errors.
- Customer Impact Duration: 22:34 UTC - 22:37 UTC (3 mins)
- Current state: See
Incident::<state>
label - Root cause: Unexpected behavior of traffic being routed to a read replica that was intentionally drained and removed from the cluster.
Timeline
View recent production deployment and configuration events (internal only)
All times UTC.
2021-06-05
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22:34
- Significant increase in error rate. -
22:35
- Drop in apdex -
22:37
- Error rate drops back to a normal state. -
22:41
- @T4cC0re declares incident in Slack. -
22:43
- Apdex recovers
Corrective Actions
Corrective actions should be put here as soon as an incident is mitigated, ensure that all corrective actions mentioned in the notes below are included.
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Incident Review
Summary
- Service(s) affected:
- Team attribution:
- Time to detection:
- Minutes downtime or degradation:
Metrics
Customer Impact
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Who was impacted by this incident? (i.e. external customers, internal customers)
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What was the customer experience during the incident? (i.e. preventing them from doing X, incorrect display of Y, ...)
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How many customers were affected?
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If a precise customer impact number is unknown, what is the estimated impact (number and ratio of failed requests, amount of traffic drop, ...)?
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What were the root causes?
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Incident Response Analysis
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How was the incident detected?
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How could detection time be improved?
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How was the root cause diagnosed?
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How could time to diagnosis be improved?
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How did we reach the point where we knew how to mitigate the impact?
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How could time to mitigation be improved?
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What went well?
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Post Incident Analysis
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Did we have other events in the past with the same root cause?
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Do we have existing backlog items that would've prevented or greatly reduced the impact of this incident?
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Was this incident triggered by a change (deployment of code or change to infrastructure)? If yes, link the issue.
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Lessons Learned
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Guidelines
Resources
- If the Situation Zoom room was utilised, recording will be automatically uploaded to Incident room Google Drive folder (private)