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https://issues.apache.org/jira/browse/HADOOP-6904?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hairong Kuang updated HADOOP-6904:
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Attachment: rpcCompatible-trunk7.patch
rpcCompatible-trunk7.patch has the following fixes:
1. rewrite ProtocolSignature#getProtocolSingature to avoid the possible
unnecessary call to getMethods.
2. use java autoboxing and unboxing whenever possible.
I still keep the protocol fingerprint cache as it is. Class does not have its
own hashCode method, so it uses the default that is based on the Class object
reference. Using it as the key does not work. Changing the value to be
ProtocolSignature also does not work because ProtocolSignature does not contain
the protocol's fingerprint.
> 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-trunk2.patch, rpcCompatible-trunk4.patch,
> rpcCompatible-trunk5.patch, rpcCompatible-trunk6.patch,
> rpcCompatible-trunk7.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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