title: Proper use of SpringRabbit DirectMessageListenerContainer and setConsumersPerQueue property
body: <p>I use the DirectMessageListenerContainer to listen to individual queues, since it creates a consumer <strong>per queue</strong>, preventing queue starvation if a messages on say "queue1" take a while to process, while the one on "queue2" are quick to process. I am confused about the <strong>DirectMessageListenerContainer.setConsumersPerQueue</strong> method. The default value is 1 looking at the source code.</p>
  
  <p>Under what conditions would one need to increase it to greater than 1? If left to default value of 1, is the processing of messages done in a multithreaded way for a given queue, if fetch size is greater than 1? </p>
  
  <pre><code>    DirectMessageListenerContainer
          listenerContainer =
          new DirectMessageListenerContainer(connectionFactory);
  
      listenerContainer.setConsumersPerQueue(10);
      listenerContainer.addQueueNames("queue1","queue2");
  
  </code></pre>