[jira] Commented: (CASSANDRA-2034) Make Read Repair unnecessary when Hinted Handoff is enabled

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-2034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12988173#action_12988173 ] 

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

This would need a separate executor for local writes that doesn't drop writes when it's behind (and blocks when it's full) to avoid problems in overcapacity situations.

I'm about halfway convinced that while blocking clients for writes to {any node in the cluster} is bad to control overload situations, blocking clients when the coordinator itself is overloaded is ok.

> 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: Jonathan Ellis
>             Fix For: 0.7.2
>
>
> 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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