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https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13080129#comment-13080129
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T Jake Luciani commented on CASSANDRA-2034:
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I think you can reuse the same RowMutation object across messages so shouldn't
cause duplicates in memory.
The only issue is if too many mutations queue up you might OOM but this is the
same problem we currently we have with the write stage. So if you use a
Expiring map you should add a onExpiration hook to write the hint locally for
the replicas that never responded to the Mutation. This covers the case that
mutations expire before a response is received.
Then all the MessageTask needs todo is clear the messageId from the expiring
map before the expiration time.
> Make Read Repair unnecessary when Hinted Handoff is enabled
> -----------------------------------------------------------
>
> Key: CASSANDRA-2034
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2034
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Patricio Echague
> Fix For: 1.0
>
> Attachments: 2034-formatting.txt, CASSANDRA-2034-trunk-v2.patch,
> CASSANDRA-2034-trunk-v3.patch, CASSANDRA-2034-trunk-v4.patch,
> CASSANDRA-2034-trunk-v5.patch, CASSANDRA-2034-trunk-v6.patch,
> CASSANDRA-2034-trunk-v7.patch, CASSANDRA-2034-trunk.patch
>
> Original Estimate: 8h
> Remaining Estimate: 8h
>
> Currently, HH is purely an optimization -- if a machine goes down, enabling
> HH means RR/AES will have less work to do, but you can't disable RR entirely
> in most situations since HH doesn't kick in until the FailureDetector does.
> Let's add a scheduled task to the mutate path, such that we return to the
> client normally after ConsistencyLevel is achieved, but after RpcTimeout we
> check the responseHandler write acks and write local hints for any missing
> targets.
> This would making disabling RR when HH is enabled a much more reasonable
> option, which has a huge impact on read throughput.
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