Dikang Gu created CASSANDRA-13611:
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Summary: Digest mismatch in Quorum read
Key: CASSANDRA-13611
URL: https://issues.apache.org/jira/browse/CASSANDRA-13611
Project: Cassandra
Issue Type: Improvement
Components: Coordination
Reporter: Dikang Gu
Assignee: Dikang Gu
In current implementation, when we issue a quorum read, C* will send full data
request to one replica, and send digest requests to other replicas. If the
digest mismatch, C* will send another round of full data request to all
replicas.
In our environment, we find in P99 case, digest are always mismatch, so we are
doing 2 round trips of requests in P99, which hurts our P99 latency a lot.
We propose that in quorum read case, we send full data replicas to the quorum
replicas directly, reconcile them and send back to client. In our experiment ,
it reduced the P99 latency by 20% ~ 30%.
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