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From Sergey_Zhemzhit...@troika.ru
Subject Re: Differences between AMQP 0.10 and AMQP 1.0
Date Wed, 26 Jan 2011 12:25:35 GMT
Gordon, 

Thanks for such a detailed answer. It's much clearer now.


Best Regards,
Sergey Zhemzhitsky




Gordon Sim <gsim@redhat.com> 
26.01.2011 15:06
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Subject
Re: Differences between AMQP 0.10 and AMQP 1.0






On 01/26/2011 06:57 AM, Sergey_Zhemzhitsky@troika.ru wrote:
> Hi there,
>
> I'm using qpid 0.6 and AMQP 0.10. Not so far ago we decided to migrate 
to
> the latest version of qpid, which currently is 0.8.
> I have looked through the AMQP 1.0 specification and discovered that 
it's
> completely different from the previous one.
> I wonder what is the analog of the exchanges and queues in the new 
version
> of specification?

The 1.0 specification is more general in the internal broker model it 
assumes. The same sorts of messaging patterns will be possible[1]. 
Brokers may chose to implement those patterns using the 
exchange-queue-binding model. Other brokers may map their pre-existing 
models to the protocol more easily as well.

The 1.0 specification is concerned with message flow between processes 
and does not mandate or constrain specific mechanisms an intermediary 
such as a broker may offer for directing the flow of messages internal 
to that process.

> In the AMQP 0.10 I was able to create a direct exchange and multiple
> bindings between it and queues. So a single message can be send to that
> exchange and it will be delivered to all the bound queues. Moreover I 
was
> able to use the same binding key to bind multiple queues to a direct
> exchange.
>
> How to emulate such a behavior by means of the address string grammar as
> described here
> 
http://qpid.apache.org/books/0.8/Programming-In-Apache-Qpid/html/ch02s04.html#section-address-string-bnf

> , without any specific definitions from the previous version of the
> specification (I mean without exchanges, queues, binding and routing
> keys)?

You can create a queue bound to a direct exchange and receive messages 
from it by using an address of the form <exchange-name>/<binding-key>.

E.g. a receiver created for amq.direct/my-subject will receive any 
message sent by some other API to the amq.direct exchange with routing 
key my-subject. [2]

This means it will receive all messages sent by a sender created for the 
same address (or indeed a sender created for any address with amq.direct 
as the name where the subject of the message is explicitly set to 
my-subject).

You can create multiple receivers like this and each one will receive 
all the relevant messages sent to that exchange. The creation of the 
subscription queue is handled by the library. If needed you can 
customise that through the link properties.

If you want to have a single receiver that can receive messages through 
a direct exchange with more than one subject, then at present you need 
to use the x-bindings element in the link properties. E.g.

amq.direct; {link: {x-bindings:[{key:abc, key:def}]}}

That is admittedly a little uglier and we want to evolve the addressing 
syntax to support a neater way for expressing more complex filters that 
a single subject or subject pattern.

While addresses of the simple form name/subject will work over AMQP 1.0 
when that is available, the address options starting with x- are all 
somewhat protocol specific. They are temporary solutions as the 
addressing evolves to cover richer cases in a protocol version neutral 
manner. However by keeping those details in a single string it makes the 
programs easier to modify.

[In all the above examples you can of course create a direct exchange 
other than amq.direct and substitute that name].

--Gordon

[1] e.g. see the interoperability tests for the 1.0 protocol: 
http://www.amqp.org/confluence/display/AMQP/1-0+Testing+Suite

[2] the spout and drain examples are useful for quickly experimenting 
with addresses.

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