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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 Mon, 15 Aug 2011 16:06:27 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13085142#comment-13085142
] 

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

I can do that.

Also, I'm not quite happy with waiting for local hints to complete per mutation. I'm thinking
of adding them to the handler so that we can wait for the hints after scheduling all the mutations.

It has pros and cons:

Pros: If the coordinator node is overwhelmed, we can tell the client right away.
Cons: Por large mutations, we are actually blocking for local hints (if any) per mutation
which is not ideal.

> 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-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-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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