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Incident documentation/2018-03-14 ORES

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Summary

We had a small and planned user facing outage during maintenance

Timeline

  • 14:18 UTC Aaron Halfaker and Alex discuss the need to do a scheduled reboot of the oresrdb hosts for kernel upgrades. Decision is taken to proceed with it ASAP
  • 14:25 UTC Alex starts with the slaves in codfw and eqiad. No impact
  • 14:34 UTC Both slaves had caught up to the masters
  • 14:34 UTC Alex starts reboots for the master redis on codfw. Errors start
  • 14:35 UTC Reboot is done but redis is loading the dataset in memory
  • 14:37 UTC oresrdb2001 has the dataset in memory, jobs can be submitted once more.
  • 14:45 UTC After having gauged the effects in codfw, alex starts the same process in eqiad
  • 14:47 UTC Icinga notices
  • 14:50 UTC Up and running again. Icinga notices

Conclusions

We were unable to serve ~2500 requests total in eqiad (~250 external ones) and ~6000 requests in codfw (~240 external ones). The reason behind this is that the redis hosts that acts both as a queue and as a cache is now a SPOF and this should be addressed.

Actionables

  • Use twemproxy for the cache redis at least in order to be able to serve at least a portion of requests during a downtime (Phab: TODO)
  • Try to figure out way that the queue redis can be made highly available (Phab: TODO)