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Date: Wed, 9 Feb 2011 17:07:58 +0000 (UTC)
From: "Hudson (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
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Subject: [jira] Commented: (HADOOP-6904) A baby step towards inter-version
 RPC communications
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    [ https://issues.apache.org/jira/browse/HADOOP-6904?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12992595#comment-12992595 ] 

Hudson commented on HADOOP-6904:
--------------------------------

Integrated in Hadoop-Hdfs-trunk-Commit #539 (See [https://hudson.apache.org/hudson/job/Hadoop-Hdfs-trunk-Commit/539/])
    

> A baby step towards inter-version RPC communications
> ----------------------------------------------------
>
>                 Key: HADOOP-6904
>                 URL: https://issues.apache.org/jira/browse/HADOOP-6904
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: ipc
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.23.0
>
>         Attachments: majorMinorVersion.patch, majorMinorVersion1.patch, rpcCompatible-trunk.patch, rpcCompatible-trunk1.patch, rpcCompatible-trunk10.patch, rpcCompatible-trunk11.patch, rpcCompatible-trunk2.patch, rpcCompatible-trunk4.patch, rpcCompatible-trunk5.patch, rpcCompatible-trunk6.patch, rpcCompatible-trunk7.patch, rpcCompatible-trunk8.patch, rpcCompatible-trunk9.patch, rpcVersion.patch, rpcVersion1.patch
>
>
> Currently RPC communications in Hadoop is very strict. If a client has a different version from that of the server, a VersionMismatched exception is thrown and the client can not connect to the server. This force us to update both client and server all at once if a RPC protocol is changed. But sometime different versions do not mean the client & server are not compatible. It would be nice if we could relax this restriction and allows us to support inter-version communications.
> My idea is that DfsClient catches VersionMismatched exception when it connects to NameNode. It then checks if the client & the server is compatible. If yes, it sets the NameNode version in the dfs client and allows the client to continue talking to NameNode. Otherwise, rethrow the VersionMismatch exception.

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