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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-252) add versioning to RPC
Date Sat, 01 Jul 2006 01:52:30 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-252?page=comments#action_12418754 ] 

Doug Cutting commented on HADOOP-252:
-------------------------------------

The way the software is currently layered, it makes sense to version the base IPC connection,
and perhaps also, in the RPC layer, to check the version of the proxy class with that of the
server instance for compatibility.  In the latter case, we might use the same mechanism a
RMI, (serialVersionUID static field, defaulting to a hash of method signatures).

> add versioning to RPC
> ---------------------
>
>          Key: HADOOP-252
>          URL: http://issues.apache.org/jira/browse/HADOOP-252
>      Project: Hadoop
>         Type: Improvement

>   Components: ipc
>     Versions: 0.3.0
>     Reporter: Yoram Arnon
>      Fix For: 0.5.0

>
> currently, any change to any rpc message breaks the protocol, with mysterious exceptions
occurring at run time.
> a versioning sceme would have two benefits:
> - intelligent error messages, indicating that an upgrade is required
> - backwards compatibility could be supported.
> the proposal is to add a "const version" for each protocol, and a method: int getVersion(int
version) that sends the client's version and receives the server's version. This would be
the first method invoked on connection. Both sides then either agree on the lowest version
number, providing backwards compatibility support, or abort the connection as "unsupported
version".

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