Incident documentation/20190611-maps

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document status: in-review

Summary

While https://phabricator.wikimedia.org/T224395 is on which led to depooling codfw. Codfw was pooled back and only two nodes were available (see Incident documentation/20190603-maps). It was necessary to reimage all codfw servers to pickup the new partitioning scheme. And when maps2003 was reimaged which was the last to reimage, kartotherian codfw which is pooled had no node to route traffic to hence request timeouts and SREs were paged. Icinga started alerting from 8:21am

Impact

Users who were currently served from codfw were affect. They were affected for about 6min(from logstash)

Detection

Icinga alerts for kartotherian endpoints. Also from pybal, no nodes were pooled at codfw due to

Timeline

All times in UTC.

  • 8:18 Reimaging of maps2003 started. OUTAGE BEGINS
  • 8:21 Icinga alerts on IRC and pages were sent out
  • 8:26 maps200[124] was pooled OUTAGE ENDS

Conclusions

What weaknesses did we learn about and how can we address them?

The following sub-sections should have a couple brief bullet points each.

What went well?

  • Outage was at least detected quickly

What went poorly?

Where did we get lucky?

  • It was easy to link outage to the ongoing reimage of maps2003

Links to relevant documentation

We should streamline processes for maps to reduce outages. Maybe via a cookbook to ensure we capture all activities and steps before performing any activity on maps.

Actionables

Explicit next steps to prevent this from happening again as much as possible, with Phabricator tasks linked for every step.

  • Streamline all maps activities via a script(cookbook) to make sure we don't miss anything?
  • Always check all asumptions (never trust any)