[AMQNET-584] CheckMessageListener throws error when any listener exists

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 1.7.2
• Component/s: NMS
• Assignee: Unassigned
• Reporter: Joshua Ingham
• Created: 23/Apr/19 16:35
• Updated: 24/Apr/19 12:42
• Resolved: 24/Apr/19 12:42

Description

When following the example provided at https://activemq.apache.org/components/nms/examples/nms-simple-asynchronous-consumer-example, I find that the consumer asynchronous listener throws an error in every case. That is:

consumer.Listener += new MessageListener(OnMessage);

The error thrown is "Cannot set Async listeners on Consumers with a prefetch limit of zero". However, I have a prefetch limit that is not zero.

I tracked down some code at https://github.com/ThorTech/apache-nms/blob/master/Apache.NMS.ActiveMQ/1.5.0/src/main/csharp/MessageConsumer.cs which suggests that the function that handles receiving messages and checks for listeners always throws an exception:

private void CheckMessageListener()
{
  if(this.listener != null)
  {
    throw new NMSException("Cannot set Async listeners on Consumers with a prefetch limit of zero");
    }

}

I understand that this may not be the most up to date code, but it would explain why I am seeing this behavior. Are asynchronous consumers actually supported? This exception, clearly out of place, suggests not, or it is a bug and nobody has stumbled upon this behaviour before.