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Investigate perf regression after elasticsearch 5.3.2 deployment
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Description

Elasticsearch 5.3.2 seems to have caused a visible perf regression on query percentiles:

  • fulltext: +20ms
  • morelike: +40ms
  • compsuggest: +2ms

Grafana - Elasticsearch Percentiles - Google Chrome_009.png (2,539×1,057 px, 310 KB)

Young GC activity seems to have jumped as well while the amount of heap used seems to have decreased:

Grafana - Elasticsearch Memory - Google Chrome_010.png (2,538×535 px, 204 KB)

Details

Event Timeline

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Change 358383 had a related patch set uploaded (by Gehel; owner: Gehel):
[operations/puppet@production] elasticsearch: remove UseConcMarkSweepGC

https://gerrit.wikimedia.org/r/358383

Gehel triaged this task as High priority.Jun 12 2017, 2:57 PM

Mentioned in SAL (#wikimedia-operations) [2017-06-13T14:22:28Z] <gehel> restarting elasticsearch on relforge to validate GC configuration - T167636

Mentioned in SAL (#wikimedia-operations) [2017-06-13T15:09:12Z] <gehel> applying new GC configuration on elastic1018 - T167636

elastic1018 is looking good, with significantly lower GC times than other nodes (see grafana). Next test is to roll out to the whole cluster...

Change 358383 merged by Gehel:
[operations/puppet@production] elasticsearch: remove UseConcMarkSweepGC

https://gerrit.wikimedia.org/r/358383

Change is merged. It will require a full cluster restart to be taken into account before we can actually close it. Cluster restart is planned to start on Monday June 19th.

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Resolving, final restart of the clusters will happen on Monday, June 19, 2017