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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 Fri, 05 Aug 2011 18:39:27 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13080137#comment-13080137
] 

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

bq. 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

Right.  Either way worst case is already "you need to be able to buffer up to rpc_timeout's
worth of writes in memory."

bq. 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

I'm not sure you want a separate ExpiringMap from the one you already have in MS.  Might make
for weird corner cases.  But that's an implementation detail; the approach is sound.

> 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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