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From Gordon Sim <g...@redhat.com>
Subject Re: Publish-Subscribe queue question
Date Wed, 03 Nov 2010 09:33:42 GMT
On 11/03/2010 01:29 AM, zhaoyi0113@gmail.com wrote:
> I have read the example for pub-sub pattern. But it doesn't use Topic, it
> uses queues. What I want is to use a Topic for pub-sub. For example, if two
> subscribers subscribe on one queue, one message will only be delivered to
> one subscriber not both of them. How can I set up a Topic in old API?

The concept of a 'topic' as JMS defines it does not directly exist in 
AMQP 0-10. Rather it is constructed by creating an distinct exclusive 
subscription queue for each subscriber, binding that to an exchange and 
then subscribing to that queue. Messages published to this exchange then 
get routed to each subscription queue and thus each subscriber sees each 
message. The subscribers are not sharing a queue, they each have their 
own queue.

When you use the Qpid JMS client, and you use a Topic, it is doing this 
work for you. The broker doesn't see a topic being used, it sees a queue 
created for each subscriber and then being bound to an exchange.

The old c++ API did not have that same functionality built in to it, so 
the application developer needed to go through the steps manually as in 
the pub-sub example. In the pub-sub example you can start multiple 
lilsteners and then when you publish messages, each listener will 
receive every published message it is interested in. This is the same 
pattern of message flow as generally implied by a JMS Topic, and the 
brokers view is the same in each case.

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