[jira] Created: (HDFS-1329) A baby step towards inter-version communications between dfs client and NameNode

["Hairong Kuang (JIRA)" <ji...@apache.org>]

A baby step towards inter-version communications between dfs client and NameNode
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                 Key: HDFS-1329
                 URL: https://issues.apache.org/jira/browse/HDFS-1329
             Project: Hadoop HDFS
          Issue Type: New Feature
          Components: hdfs client
    Affects Versions: 0.22.0
            Reporter: Hairong Kuang
            Assignee: Hairong Kuang
             Fix For: 0.22.0


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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