Correspondence Regarding Restart as Diagnosis
The service was not behaving correctly. It was restarted. It is now behaving correctly. The reason it was not behaving correctly is no longer determinable.
FROM: On-call engineer TO: Incident retrospective RE: 2:14am incident — service restart
At 2:14am, the primary service began returning 503 errors. I was paged. I reviewed the available metrics: CPU normal, memory elevated but within bounds, no obvious configuration change in the last deploy.
I restarted the service at 2:15am.
The service recovered at 2:16am. All requests resolved normally. I monitored for forty-five minutes. No recurrence.
I do not know what caused the error.
FROM: Incident retrospective team TO: On-call engineer RE: Re: 2:14am incident
Thank you for the response. To complete the retrospective, we need the root cause. The restart resolved the symptom. What was causing the 503s?
FROM: On-call engineer RE: Re: Re: 2:14am incident
I have reviewed the available logs. The logs from 2:14am were rotated when the service restarted. The metrics from the period show elevated memory, but memory returned to normal after restart, which could indicate a memory leak, a temporary spike, or normal flush behavior on restart.
There is also the possibility that the 503s were unrelated to memory and were caused by a connection pool exhaustion, a downstream dependency timeout, or a transient network issue. These would all resolve on restart and would leave no distinguishing evidence.
The root cause is: restart resolved it.
FROM: Incident retrospective team RE: Follow-up
"Restart resolved it" is an outcome, not a cause. Please specify the cause.
FROM: On-call engineer
I understand. The cause was a condition that existed in the running service and was cleared by the restart. The condition cannot be identified from the evidence available because the restart cleared the evidence along with the condition.
I recommend: increase log retention. Otherwise this conversation will occur again.
FROM: Incident retrospective team
Root cause logged as: undetermined. Mitigation: restart. Action item: log retention review.
The service is working.