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From "Patricio Echague (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2034) Make Read Repair unnecessary when Hinted Handoff is enabled
Date Tue, 16 Aug 2011 21:16:29 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13085978#comment-13085978
] 

Patricio Echague commented on CASSANDRA-2034:
---------------------------------------------

{quote}
Also, still need to address this:

currentHintsQueueSize [now totalHints] increment needs to be done OUTSIDE the runnable or
it will never get above the number of task executors
{quote}

hintsInProgress.incrementAndGet(); happens outside of the executor and actually before scheduling
it.
totalHints.incrementAndGet(); on the other hand, the totalHint is incremented right after
the hint was written and within the task.

Is that not right ?

> 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, 2034-v16.txt, CASSANDRA-2034-trunk-v10.patch,
CASSANDRA-2034-trunk-v11.patch, CASSANDRA-2034-trunk-v11.patch, CASSANDRA-2034-trunk-v12.patch,
CASSANDRA-2034-trunk-v13.patch, CASSANDRA-2034-trunk-v14.patch, CASSANDRA-2034-trunk-v15.patch,
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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