[rabbitmq-discuss] JMS/AMQP use case

[Alexis Richardson]

Jan,

Thanks for your question.

On Tue, Jan 5, 2010 at 7:32 AM, Jan Van Besien <janvanbesien at gmail.com> wrote:
> Hi all,
>
> We currently use JMS between a lot of internal components, and also
> expose a JMS interface externally (a set of topics) to our customers. As
> JMS is a Java only thing, we are looking into language neutral
> alternatives for the customer facing interface. The AMQP standard seems
> to fit our needs, but I haven't figured out yet what the ideal
> deployment scenario (with rabbitMQ) would be.
>
> Is it possible (and desirable) to continue using JMS internally (without
> rabbitMQ) in a first phase, and have an AMQP interface on top of it?

Yes and no ;-)

It's not really possible to do this in an elegant ('built in to the
broker') way at the moment.  The AMQP model is more general than JMS,
making it hard to model AMQP from JMS without (in effect) building a
Java AMQP broker from scratch.  On the other hand, because AMQP is
more general than JMS, providing a JMS interface to an AMQP broker has
been done, modulo some warts and gotchas.

It may get easier to expose AMQP interfaces to JMS brokers when we
finally reach AMQP 1.0.  This is intended to be factored in such a way
that 'legacy' message brokers can expose AMQP message formats but not
full behaviours.  This would be similar, in effect, to how a JMS
broker might expose a STOMP interface today.

That said....

> If
> so, could you give me some hints on how the setup would be than.

Despite my remarks above, about AMQP being more general than JMS, this
is certainly something you could try.  Let's say you want to run JMS
as your core system and gradually layer AMQP on top of it.  You could:

1. Install and run RabbitMQ
2. Set up some queues and bindings (perhaps, one for each of your public topics)
3. Publish AMQP messages to RabbitMQ
4. Consume AMQP messages from RabbitMQ using a Java client.
5. In the same Java client, create JMS messages from the payloads of
the AMQP and forward them to your JMS system

You could do the above yourself, and it would work, but with some
drawbacks I am sure I don't need to enumerate.  Indeed, this approach
could potentially be extended to something a bit more robust.

*Alternatively*

Have you looked at STOMP?  If your infra requires JMS based messaging
inside for some time, then STOMP is one way to cross the language
barrier.  It's not as powerful as AMQP for defining broker behaviour
(routing, delivery, qos), but, you don't always need that.





> I guess
> I need to deploy the rabbitMQ server, and develop some component which
> makes the "bridge" between JMS and AMQP (listening to incoming JMS
> messages and "forwarding" them to the rabbitMQ server or something like
> that).

Well, now you are asking a different question :-)

Above I described how to expose a JMS infra using some sort of AMQP
gateway, so that you could send messages to RabbitMQ in AMQP and
forward them to JMS brokers.

If you want to do this the other way round, ie. send JMS messages to
RabbitMQ, then you can use the JMS client.

Note that:

1) Because JMS is an API not a protocol, it is possible to expose it
on the client side 100%, and use any protocol you like to communicate
between your JMS client and your broker.  This by the way raises the
question "what is a JMS broker?".  And the answer is: "something that
has a JMS client".  Go figure.

2) Because AMQP's model is somewhat different from JMS, not all of the
JMS 'TCK' API is modelled in the current JMS clients.

3) Not very many people use JMS with RabbitMQ, so I am not sure what
currently works with what.

Here is a 'how to' -
http://www.lshift.net/blog/2009/03/16/openamqs-jms-client-with-rabbitmq-server

We hope to make all this much easier to run OOTB very soon.



> Does this sound like a good idea at all, or should I maybe try to use
> rabbitMQ as the underlying implementation for the internal JMS as well?

Honestly, it depends on your use case and the extent to which your
existing messaging infra is welded into place.

At this stage I would recommend *experimenting* with some of the
approaches I described above.  By all means ask any question on this
list if you get stuck.


> I'm sorry if these are newbie questions... The individual pieces of
> documentation seem comprehensive enough, but I currently fail to get the
> overall idea of how to apply it to my use case (could be me of course).

I am sorry the JMS-AMQP thing is not as clear as it could be.

alexis



> Thanks in advance,
> Jan
>
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