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https://issues.apache.org/jira/browse/CASSANDRA-13577?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benjamin Lerer updated CASSANDRA-13577:
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Status: Open (was: Patch Available)
> Fix dynamic endpoint snitch for sub-millisecond use case
> --------------------------------------------------------
>
> Key: CASSANDRA-13577
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13577
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/Streaming and Messaging
> Reporter: Simon Zhou
> Assignee: Simon Zhou
> Priority: Normal
> Fix For: 3.0.x
>
>
> This is a follow up of https://issues.apache.org/jira/browse/CASSANDRA-6908.
> After disabling severity (CASSANDRA-11737/CASSANDRA-11738) in a few
> production clusters, I observed that the scores for all the endpoints are
> mostly 0.0. Through debugging, I found this is caused by that these clusters
> have p50 latency well below 1ms and the network latency is also <0.1ms (round
> trip). Be noted that we use p50 sampled read latency and millisecond as time
> unit. That means, if the latency is mostly below 1ms, the score will be 0.
> This is definitely not something we want. To make DES work for these
> sub-millisecond use cases, we should change the timeunit to at least
> microsecond, or even nanosecond. I'll provide a patch soon.
> Evidence of the p50 latency:
> {code}
> nodetool tablehistograms <keyspace> <table>
> Percentile SSTables Write Latency Read Latency Partition Size
> Cell Count
> (micros) (micros) (bytes)
>
> 50% 2.00 35.43 454.83 20501
> 3
> 75% 2.00 42.51 654.95 29521
> 3
> 95% 3.00 182.79 943.13 61214
> 3
> 98% 4.00 263.21 1131.75 73457
> 3
> 99% 4.00 315.85 1358.10 88148
> 3
> Min 0.00 9.89 11.87 61
> 3
> Max 5.00 654.95 129557.75 943127
> 3
> {code}
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