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

          Resolution: Fixed
       Fix Version/s: 2.6.0
                      3.0.0
    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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