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Message-ID: <15633684.258421294685208587.JavaMail.jira@thor>
Date: Mon, 10 Jan 2011 13:46:48 -0500 (EST)
From: "Hairong Kuang (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Subject: [jira] Updated: (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:all-tabpanel ]

Hairong Kuang updated HADOOP-6904:
----------------------------------

    Attachment: rpcCompatible-trunk4.patch

This patch in addition does
1. Make sure hashcode of an array of methods is irrelavant of the methods order in the array.
2. A method's hashcode also includes its returning type.
3. Add method hashcode unit test.

> 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: 0.22.0
>
>         Attachments: majorMinorVersion.patch, majorMinorVersion1.patch, rpcCompatible-trunk.patch, rpcCompatible-trunk1.patch, rpcCompatible-trunk2.patch, rpcCompatible-trunk4.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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