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Ian Barfield commented on CASSANDRA-6591: ----------------------------------------- The "hit mva / rate mva" and "hit rate mva" as you define them are indeed very different things. This is most likely intentional and I would say desirable. The red line "hit rate mva" seems to be applying the idea of recency to a metric that already has a recency window (in this case the window is 'all time'). This strikes me as both unintuitive and unhelpful; after the metrics have been going for a while it is unlikely to change very fast, and by making it a moving average it will change even slower. You could easily have a 100% miss ratio for several minutes and never see that line move. That seems to defeat the purpose of having a "recent" hitRate metric. As for EWMAs being 'comparable': I'm not certain on the exact mathematical implications of dividing two estimates after sampling, but I strongly suspect it would be more than accurate enough for this purpose. > un-deprecate cache recentHitRate and expose in o.a.c.metrics > ------------------------------------------------------------ > > Key: CASSANDRA-6591 > URL: https://issues.apache.org/jira/browse/CASSANDRA-6591 > Project: Cassandra > Issue Type: Improvement > Components: Core > Reporter: Chris Burroughs > Assignee: Chris Burroughs > Priority: Minor > Attachments: j6591-1.2-v1.txt, j6591-1.2-v2.txt, j6591-1.2-v3.txt > > > recentHitRate metrics were not added as part of CASSANDRA-4009 because there > is not an obvious way to do it with the Metrics library. Instead hitRate was > added as an all time measurement since node restart. > This does allow changes in cache rate (aka production performance problems) > to be detected. Ideally there would be 1/5/15 moving averages for the hit > rate, but I'm not sure how to calculate that. Instead I propose updating > recentHitRate on a fixed interval and exposing that as a Gauge. -- This message was sent by Atlassian JIRA (v6.2#6252)