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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10597) Evaluate if we can have RPC client back off when server is under heavy load
Date Mon, 28 Jul 2014 23:55:40 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14077154#comment-14077154
] 

Jing Zhao commented on HADOOP-10597:
------------------------------------

This can be a very useful feature. For the evaluation, maybe It will be helpful to see how
the change will affect the request latency and NN throughput when the workload of NN increases
from low to high. For example, one of my questions is that when the NN workload is just relatively
high (there are some but not many requests are blocking on the queue), will the average latency
and throughput be affected if NN directly lets client back off instead of blocking and timeout?

> Evaluate if we can have RPC client back off when server is under heavy load
> ---------------------------------------------------------------------------
>
>                 Key: HADOOP-10597
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10597
>             Project: Hadoop Common
>          Issue Type: Sub-task
>            Reporter: Ming Ma
>            Assignee: Ming Ma
>         Attachments: HADOOP-10597-2.patch, HADOOP-10597.patch, RPCClientBackoffDesignAndEvaluation.pdf
>
>
> Currently if an application hits NN too hard, RPC requests be in blocking state, assuming
OS connection doesn't run out. Alternatively RPC or NN can throw some well defined exception
back to the client based on certain policies when it is under heavy load; client will understand
such exception and do exponential back off, as another implementation of RetryInvocationHandler.



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