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https://issues.apache.org/jira/browse/CASSANDRA-12940?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tom van der Woerdt updated CASSANDRA-12940:
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Reproduced In: 3.0.9
> Large compaction backlogs should slow down repairs
> --------------------------------------------------
>
> Key: CASSANDRA-12940
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12940
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Tom van der Woerdt
>
> Repairs cause a flood of small sstables. In some situations the small
> sstables come in so fast that it takes longer to commit the compaction
> transaction than it takes to stream in the tables. This will cause a buildup
> in sstables, and this buildup causes compaction to go even slower (see
> CASSANDRA-12764).
> For a cluster of mine this means running into nodes with >100 loadavg, with
> tables that have 10k sstables. After the repair finishes the nodes go back to
> normal, but it takes a while and affects query latency a lot.
> The compaction paths could probably be faster, though I'm more interested in
> making repairs wait for compaction. When we have a L0 with 10000+ tables, the
> repair path should probably wait a minute.
> All I did was run 'nodetool repair' :
> {noformat}
> SSTable count: 11755
> SSTables in each level: [11709/4, 23/10, 50, 0, 0, 0, 0, 0, 0]
> {noformat}
> `nodetool compactionstats' shows 17 pending tasks (seems a bit low) and
> `nodetool netstats' shows 1861 lines of text over 138 stream sessions.
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