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Incidents/2019-04-07 Zotero

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On the morning of April 7, most of the zotero pods in codfw started using too much memory, and stopped responding to requests.


Given restbase and citoid are active/active, any user coming from eqsin, codfw or ulsfo and trying to get a citation would have seen a degraded service.


The LVS level check of zotero, and the service-checker test of citoid both reported the issue.


All times in UTC.

  • 04:58 sudden increase in the memory used by the first zotero pod
  • 05:05 all zotero pods in codfw have now high memory watermark. Service checker on citoid reports a problem
  • 05:12 The zotero LVS endpoint has become unresponsive to monitoring. A page is sent. OUTAGE BEGINS
  • 05:13 A recovery page arrives. The service will keep flapping and more pages are sent out 5:23 (recovery at 5:37), at 5:41 (recovery at 5:42) at 6:00
  • 06:01 Alexandros, Giuseppe and marostegui respond to the page that is now being sent to people in EU timezones
  • 06:03 Giuseppe depools zotero in codfw, even if the recovery arrives, so that the issue can be better analyzed. OUTAGE ENDS
  • 06:23 After some log analysis, it is decided to kill the pods which still show a high memory watermark.


There isn't much to conclude, apart from the fact we still have situations where zotero can fail because of sudden memory increases. This is a bug in the software and unless we can create a reproducible test case (as this seems to happen because of some user request), there aren't many chances to see it fixed. On the positive side, this hadn't happened in a long time.

The root cause of this specific incident is still TBD.

What went well?

  • The problem is known, the monitoring adequate, the response clear. This isn't a new kind of outage and we're well equipped to respond to it.

What went poorly?

  • No reponse to repeated pages/recoveries for almost 1 hour.
  • No runbook exists for this

Where did we get lucky?

Links to relevant documentation

AIUI the documentation on how to operate on kubernetes for debugging should be written this quarter.


  • Document kubernetes debugging procedures (TODO: Create task)
  • Identify and reproduce the situation that caused the memory leak (TODO: Create task)