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From Gordon Sim <g...@redhat.com>
Subject Re: Address of default no-name exchange
Date Wed, 29 Jun 2011 12:06:15 GMT
On 06/29/2011 12:55 PM, Jiri Krutil wrote:
>> The assumption there is that senders are expensive to create?
>
> Yes. Are they? (I always specify the node type, so hopefully no need for
> a broker roundtrip)

No, I don't think they are. Especially as you are specifying the node 
type to avoid having to look that up. It will do a synchronous, passive 
queue declare at present. The reason for that is simply to ensure the 
address is valid before you start sending. I could imagine having some 
way to disable that or make it async if it proves a problem.

>> The reply-to address doesn't have to be a queue of course, to be
>> completely generic it should handle any exchange/routing-key pair (at
>> least in AMQP 0-10).
>
> OK, didn't know that. I wanted to check if this is also the case for
> AMQP 0-9-1, but could not find that info in the specs. Do you know?

Prior to 0-10 it was documented as 'the destination to reply to' which 
would imply it should contain an exchange name. Obviously this was not 
precise enough for many cases which is why it was refined a little for 0-10.

> Which Address attributes are relevant for the parameter of
> Message::setReplyTo() - name, type, subject?

Yes, those are the three attributes that are relevant.

>>> Let's say I create a Sender for queue A. It will actually point to the
>>> default exchange with the routing key defaulting to A, right?
>>
>> No, the messaging library resolves an address to a particular broker
>> entity. If the name matches a queue, then it assumes you want to send
>> to the queue. If the name matches an exchange then it assumes you want
>> to send to the exchange.
>
> OK, coming back to the original question: is there a way how to create a
> Sender pointing to the default exchange?

No. The messaging API doesn't treat the default exchange as an 
addressable node in its own right.

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