Open Stack

HI 

>AFAIK, amqp only uses the exchange as a dispatcher and all storage is done in
>the queue ... but I could be wrong. I vaguely recall there being a durable
>exchange setting as well as durable queue.

AFAIK if a message can't be routed there are three options:
 - the message is discarded (I think this is the default option)
-  the message is sent back to the publisher (some params need to be specified when a message is published)
- some broker can have specific queues for those messages, for example Rabbitmq has a "dead letter queue" where not routable messages are stored.

Durable exchanges are exchanges that survive to a server restart, they don't need to be re-declared.
HTH
--
Andrea Rosa