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Date: Fri, 26 Aug 2011 19:17:29 +0000 (UTC)
From: "Matt Foley (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HADOOP-6889) Make RPC to have an option to
 timeout
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    [ https://issues.apache.org/jira/browse/HADOOP-6889?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13091963#comment-13091963 ] 

Matt Foley commented on HADOOP-6889:
------------------------------------

That was a +1 on the patch for branch-0.20-security.

> Make RPC to have an option to timeout
> -------------------------------------
>
>                 Key: HADOOP-6889
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6889
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: ipc
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: John George
>             Fix For: 0.20-append, 0.20.205.0, 0.22.0
>
>         Attachments: HADOOP-6889-for-20security.patch, HADOOP-6889-for20.2.patch, HADOOP-6889-for20.3.patch, HADOOP-6889-for20.patch, HADOOP-6889-fortrunk.patch, HADOOP-6889.patch, ipcTimeout.patch, ipcTimeout1.patch, ipcTimeout2.patch
>
>
> Currently Hadoop RPC does not timeout when the RPC server is alive. What it currently does is that a RPC client sends a ping to the server whenever a socket timeout happens. If the server is still alive, it continues to wait instead of throwing a SocketTimeoutException. This is to avoid a client to retry when a server is busy and thus making the server even busier. This works great if the RPC server is NameNode.
> But Hadoop RPC is also used for some of client to DataNode communications, for example, for getting a replica's length. When a client comes across a problematic DataNode, it gets stuck and can not switch to a different DataNode. In this case, it would be better that the client receives a timeout exception.
> I plan to add a new configuration ipc.client.max.pings that specifies the max number of pings that a client could try. If a response can not be received after the specified max number of pings, a SocketTimeoutException is thrown. If this configuration property is not set, a client maintains the current semantics, waiting forever.

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