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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2034) Make Read Repair unnecessary when Hinted Handoff is enabled
Date Wed, 10 Aug 2011 17:22:27 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082492#comment-13082492
] 

Jonathan Ellis commented on CASSANDRA-2034:
-------------------------------------------

bq. I don't think local hints need to be put on their own queue / thread-pool. Just write
the hint to the local mutation queue and increment the hint counters

Agreed, that is a better solution than complicating things with extra queues / executors.
 Since the message dropping is done by the Task, not the executor, there's no problem in that
respect.  And we can use a simple counter to avoid clogging the queue with hints.

> 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-v8.patch, CASSANDRA-2034-trunk-v9.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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