[jira] [Created] (CASSANDRA-7545) Hints for a down node are written to a single partition in system.hints on the coordinator leading to contention

["graham sanderson (JIRA)" <ji...@apache.org>]

graham sanderson created CASSANDRA-7545:
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             Summary: Hints for a down node are written to a single partition in system.hints on the coordinator leading to contention
                 Key: CASSANDRA-7545
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7545
             Project: Cassandra
          Issue Type: Bug
            Reporter: graham sanderson


The worst side effect is potentially orders of magnitude larger than suspected memory allocation due to a race condition updating the columns in the memtable.

That said, having so many hints in a single partition has other negative side effects (non linear growth of sorted tree data structure overhead in memtable, just plain large number of tombstones in a row etc.)

Ideally, the hints would be partitioned by both the nodeUUID, and a fixed number of (say 4) bits of a hash of the original rowmutation's partition key... even this small spreading of load has a significant improvement.



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