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From Rob Godfrey <rob.j.godf...@gmail.com>
Subject Re: Java broker exchange questions
Date Sun, 10 Mar 2013 09:51:47 GMT
On 10 March 2013 09:42, Fraser Adams <fraser.adams@blueyonder.co.uk> wrote:
>> Yeah - from an AMQP 1.0 point of view one might consider Queues and
>> Exchanges both as types of "Nodes" (the 1.0 transport for the Java
>> Broker actually allows you to publish directly to Queues and subscribe
>> to Exchanges)... how to present this and the 0.x view as a single
>> coherent model will be "interesting" (are bindings links from
>> exchanges to queues I wonder)
> As per previous post I'm *really* interested in this going forward as I
> suspect are many people. Publishing to a queue seems fairly "normal" given
> that the default direct exchange provided a mechanism to use a producer
> address that just looked like a queue, but subscribing to an exchange seems
> weirder. In the latter case clearly a topic address made it look like this
> was happening, but a temporary queue was always put in place *actually*
> subscribing to exchanges seems more unusual as one would normally expect
> some sort of "elastic" buffering to decouple producers and consumers. I
> guess that with Qpid there's the concept of prefetching messages so I guess
> that this gives the necessary buffering (unless synchronous behaviour has
> been specified).
> I'd really like to understand more about how this is currently working in
> AMQP 1.0/Proton do you have some example Addresses that are being used - I'm
> particularly interested in how an existing AddressString containing a
> headers exchange and bindings to that might work.

So, what the Java Broker does under the covers is actually to create a
temporary subscription queue.  One could actually implement
subscriptions to exchanges such that published messages are not
acknowledged until they have been flowed to all recipients... but that
would have been a bigger piece of work.

Ultimately I want to just add "topic" nodes rather than abusing
exchanges for this purpose (I had a 10 line patch that did this that
is probably still sitting around somewhere). The primary
implementation difference is that  messages at the head of a "topic"
get silently dropped if there are no subscriptions that have not yet
passed that message.

>> -- Rob (going seriously off-topic)
> Perhaps, but it's probably a good topic to start, the AMQP 1.0 work has been
> quietly going on in dev land and I think this is probably a good time to
> start sharing the love a bit on the user list.

+1.  We definitely need to talk more about AMQP 1.0 on this list as
well as better explaining what things are AMQP 1.0 and what things are

-- Rob

> Frase
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