[jira] [Updated] (CASSANDRA-13736) CASSANDRA-9673 cause atomic batch p99 increase 3x

["C. Scott Andreas (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-13736?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

C. Scott Andreas updated CASSANDRA-13736:
-----------------------------------------
    Component/s: Coordination

> CASSANDRA-9673 cause atomic batch p99 increase 3x
> -------------------------------------------------
>
>                 Key: CASSANDRA-13736
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13736
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Coordination
>            Reporter: xiangzhou xia
>            Assignee: xiangzhou xia
>            Priority: Major
>
> When we testing atomic batch in production traffic, we found that p99 latency in atomic batch write is 2x-3x worse than 2.2. 
> After debuging, we found that the regression is causing by CASSANDRA-9673. This patch changed consistency level in batchlog store from ONE to TWO. [~iamaleksey] think only block for one batchlog message is a bug in batchlog and change it to block for two in CASSANDRA-9673, I think it's actually a very good optimization to reduce latency. 
> Set the consistency to one will decrease the possibility of slow data node (GC, long message queue, etc) affect the latency of atomic batch.  In our shadow cluster, when we change consistency from two to one, we notice a 2x-3x p99 latency drop in atomic batch.   



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