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https://issues.apache.org/jira/browse/HDFS-1329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12894897#action_12894897
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Tsz Wo (Nicholas), SZE commented on HDFS-1329:
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Could you provide a few examples of compatible changes to ClientProtocol? I
wonder how could a DfsClient check whether it is compatible to the server. Are
there rules? or just by a hard coded compatibility list?
The description is quite abstract. I do not understand what are the goals.
Could you tell us your use cases?
> A baby step towards inter-version communications between dfs client and
> NameNode
> --------------------------------------------------------------------------------
>
> 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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