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h2. General Information

The Qpid M3 release introduces priority queues into the Java Messaging Broker, supporting JMS clients who wish to make use of priorities in their messaging implementation.

There are some key points around the use of priority queues in Qpid, discussed in the sections below.
 
h2. Defining Priority Queues

It is possible to define a queue as a priority queue in the virtualhost configuration file. When defining the queue, add a <priority>true</priority> element. This will ensure that the queue has 10 distinct priorities, which is the number supported by JMS.

If you require fewer priorities, it is possible to specify a "<priorities>/{int/}</priorities>" element which will give the queue that number of distinct priorities. When messages are sent to that queue, their effective priority will be calculated by partitioning the priority space. If the number of effective priorities is 2, then messages with priority 0-4 are treated the same and messages with priority 5-9 are treated equivalently. 

{code:xml}

        <queue>
          <name>test</name>
          <test>
            <exchange>amq.direct</exchange>
            <priority>true</priority>
          </test>
        </queue>
{code}