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https://issues.apache.org/jira/browse/CASSANDRA-14293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16410167#comment-16410167
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Michael Kjellman commented on CASSANDRA-14293:
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changes look fine to me. let's get this committed on to trunk to start with so
we can start working on a 3.0 version...
> Speculative Retry Policy Should Support Specifying MIN/MAX of 2 PERCENTILE
> and FIXED Policies
> ---------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-14293
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14293
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Michael Kjellman
> Assignee: Michael Kjellman
> Priority: Major
> Fix For: 4.x
>
>
> Currently the Speculative Retry Policy takes a single string as a parameter,
> this can be NONE, ALWAYS, 99PERCENTILE (PERCENTILE), 50MS (CUSTOM).
> The problem we have is when a single host goes into a bad state this drags up
> the percentiles. This means if we are set to use p99 alone, we might not
> speculate when we intended to to because the value at the specified
> percentile has gone so high.
> As a fix we need to have support for something like min(99percentile,50ms)
> this means if the normal p99 for the table is <50ms, we will still speculate
> at this value and not drag the happy path tail latencies up... but if the
> p99th goes above what we know we should never exceed we use that instead.
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