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From "Yoram Arnon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-252) add versioning to RPC
Date Thu, 29 Jun 2006 06:20:30 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-252?page=comments#action_12418394 ] 

Yoram Arnon commented on HADOOP-252:
------------------------------------

having a handshake when setting up a connection is fairly standard.
Both sides may either agree on the lowest common denominator, and send messages in a previously
supported format, or decide to throw. It's better than a version in each message for two reasons:
1(minor) a few bytes less per message
2(major) allows a new component to avoid sending new messages to an old component, that doesn't
support it.

> 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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