[jboss-user] [JBoss Messaging] - Re: JMSMessageID in Messaging cluster

[aslak]

As far as the JMS 1.1 Specification goes on the topic:

----------------------------
3.4.3 JMSMessageID
	
	The JMSMessageID header field contains a value that uniquely identifies each
	message sent by a provider.
	...

	A JMSMessageID is a String value which should function as a unique key for
	identifying messages in a historical repository. The exact scope of uniqueness is
	provider defined. It should at least cover all messages for a specific installation
	of a provider where an installation is some connected set of message routers.
	...

3.4.5 JMSCorrelationID

	A client can use the JMSCorrelationID header field to link one message with
	another. A typical use is to link a response message with its request message.
	...

	Since each message sent by a JMS provider is assigned a message ID value, it is
	convenient to link messages via message ID.
	...

	In some cases, an application (made up of several clients) needs to use an
	application-specific value for linking messages.
	...

----------------------------

I'm not 100% sure, but I think the text 'a specific installation of a provider where an installation is some connected set of message routers'
could be hinting at a cluster?

The specification is clear that a MessageID is suppose to uniquely identify a Message. By changing the MessageID 
it no longer identifies the original Message. It now identifies a new Message, unknown to the sender.

Common Practice...

The two common correlation patterns are:
 - Correlation ID Pattern 
	The receiver copies the request Correlation ID to the response Correlation ID.

 - Message ID Pattern
	The receiver copies the request Message ID to the response Correlation ID.


I think it would be wrong of the JMS provider to force the use of one over the other.


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