3.3. Delivery guarantees

A key feature of most messaging systems is reliable messaging. With reliable messaging the server gives a guarantee that the message will be delivered only once to each consumer of a queue or each durable subscription of a topic, even in the event of system failure. This is crucial for many businesses; you do not want your orders fulfilled more than once or any of your orders to be lost, for example.

In other cases you may not care about a once only delivery guarantee and are happy to cope with duplicate deliveries or lost messages. An example of this might be transient stock price updates, which are quickly superseded by the next update on the same stock. The messaging system allows you to configure which delivery guarantees you require.