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From "Arpit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HADOOP-8069) Enable TCP_NODELAY by default for IPC
Date Tue, 29 Jul 2014 03:01:48 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-8069?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Arpit Agarwal resolved HADOOP-8069.

          Resolution: Fixed
       Fix Version/s: 2.6.0
    Target Version/s: 2.6.0  (was: 2.0.0-alpha, 3.0.0)
        Release Note: This change enables the TCP_NODELAY flag for all Hadoop IPC connections,
hence bypassing TCP Nagling. Nagling interacts poorly with TCP delayed ACKs especially for
request-response protocols.
        Hadoop Flags: Reviewed

Committed to trunk and branch-2, resolving with release note.

> Enable TCP_NODELAY by default for IPC
> -------------------------------------
>                 Key: HADOOP-8069
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8069
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: ipc
>    Affects Versions: 0.23.0, 2.4.1
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: 3.0.0, 2.6.0
>         Attachments: hadoop-8069.txt
> I think we should switch the default for the IPC client and server NODELAY options to
true. As wikipedia says:
> {quote}
> In general, since Nagle's algorithm is only a defense against careless applications,
it will not benefit a carefully written application that takes proper care of buffering; the
algorithm has either no effect, or negative effect on the application.
> {quote}
> Since our IPC layer is well contained and does its own buffering, we shouldn't be careless.

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