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2020-09-07 degredation in sidekiq apdex, caused by a saturation of shard_urgent_cpu_bound, caused by performance issues with UpdateMergeRequestsWorker

Summary

2020-09-07 sidekiq errors

Degredation in sidekiq apdex, caused by a saturation of shard_urgent_cpu_bound, caused by performance issues with UpdateMergeRequestsWorker

Timeline

All times UTC.

2020-xx-xx

2020-09-07

  • 09:05 - a particularly bad case of poor performance of this worker begins, these jobs run for a very long time (as already reported in the issue linked above), other jobs in the shard_urgent_cpu_bound are enqueued
  • 09:06 - apdex begins to degrade
  • 09:23 - the faulty jobs finish running, the queues are still high, workers start crunching through the queues
  • 09:25 - the EOC is paged for an SLO alert, at this point the queues are almost empty and the workers are almost finished catching up with the backlog
  • 09:27 - mwasilewski declares incident in Slack using /incident declare command.
  • 09:30 - apdex recovers, the alert clears

Click to expand or collapse the Incident Review section.

Incident Review

Summary

  1. Service(s) affected:
  2. Team attribution:
  3. Minutes downtime or degradation:

Metrics

Customer Impact

  1. Who was impacted by this incident? (i.e. external customers, internal customers)
  2. What was the customer experience during the incident? (i.e. preventing them from doing X, incorrect display of Y, ...)
  3. How many customers were affected?
  4. If a precise customer impact number is unknown, what is the estimated potential impact?

Incident Response Analysis

  1. How was the event detected?
  2. How could detection time be improved?
  3. How did we reach the point where we knew how to mitigate the impact?
  4. How could time to mitigation be improved?

Post Incident Analysis

  1. How was the root cause diagnosed?
  2. How could time to diagnosis be improved?
  3. Do we have an existing backlog item that would've prevented or greatly reduced the impact of this incident?
  4. Was this incident triggered by a change (deployment of code or change to infrastructure. If yes, have you linked the issue which represents the change?)?

5 Whys

Lessons Learned

Corrective Actions

Guidelines

Edited by Michal Wasilewski