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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-10597) Evaluate if we can have RPC client back off when server is under heavy load
Date Wed, 07 Jan 2015 05:28:35 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-10597?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Ming Ma updated HADOOP-10597:
    Attachment: HADOOP-10597-4.patch

Thanks, [~stevel@apache.org]! Here is the new patch with your suggestions.

Regarding the serialization of {{RetryAction}} via {{RetriableException}} message string,
I agree it is not necessarily the best approach. Here we need to serialize RetryAction and
have RPC server send it back to RPC client. Possible options that I know of:

* Current RPC Header structure {{RpcHeaderProtos}} includes Exception message field; thus
it is convenient to use {{RetriableException}} message.
* We can consider adding optional {{RetryAction}} field into RPC header {{RpcHeaderProtos}}.
That requires more changes.

> 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: Steve Loughran
>         Attachments: HADOOP-10597-2.patch, HADOOP-10597-3.patch, HADOOP-10597-4.patch,
HADOOP-10597.patch, MoreRPCClientBackoffEvaluation.pdf, 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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