Discussion "Topics" for this morning's queue discussion

["David A. Chappell" <chappell@sonicsoftware.com>]

Here are some discussion points to be used for this morning's time slot for queue support -

 

1) When a subscriber subscribes, should  it expect to receive messages that were published before the subscription took place?  If queuing semantics were being used underneath the subscription model, then there could be messages queued up that are waiting to be consumed (waiting for hours, days, weeks).

 

2) In JMS there is a notion of a durable subscription, where a subscriber can go offline and have messages queued for it on its behalf while it is unavailable.  Should  we have something comparable in WS-N?

 

2a) If so, then do we need to have a concept of subscriber affinity?

 

3) exactly-once delivery is a generally accepted trait of queues.  A common implementation pattern is load-balanced queue receivers, where multiple receivers listen on the same queue, yet only one of them will receive each individual message.  If I were to overlay WS-N pub/sub topics onto queues in this situation, that would imply a consumption pattern where multiple consumers can subscribe to a given 'Topic', yet only one would recieve each message.  That is really exactly-one receiver.  Should that be tied to exactly-once delivery?

 

3a) That being said: Even in the current draft spec we don't explicity say that in the pub/sub model, all active subscribers are expected to receive a copy of the same message.

 

4) Pull-type message delivery (Peter) 

 

5) Policy assertions or WSDL definitions.

 

6) Composability with WS-Rel*.  Do we need to do anything here, or is it implied?

 

7) We currently manage namespaces for topics.  Should we have something special for handling namespaces for point-to-point messaging destinations, or is that simply what web services are for?

 

Dave

 

 

 

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Dave Chappell [weblog] Vice President and Chief Technology Evangelist Technology Advancement Group, Sonic Software Corporation author, "Enterprise Service Bus" (O'Reilly) co-author,"Java Web Services" (O'Reilly), "The Java Message Service" (O'Reilly), "Professional ebXML Foundations", (Wrox Press) p. 781-999-7099 mobile 617-510-6566 e. chappell@sonicsoftware.com

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