[AMQ-3720] ActiveMqMessageConsumer should have a blocking message wait that does not require Session synchronization

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Not A Problem
• Fix Version/s: 5.6.0
• Component/s: JMS client
• Assignee: Unassigned
• Reporter: Martin Serrano
• Created: 15/Feb/12 21:03
• Updated: 16/Feb/12 20:55
• Resolved: 16/Feb/12 20:55

Description

According to the documentation I've read and response to message posts, I've concluded that a call to consumer.receive(long) must guard against another thread using the session the consumer was created with.

This makes it difficult to write performant code because a busy-wait idiom must be used in order to not hold a lock on session access while waiting for new messages. I've implemented a new method that will block until messages are available but does not require a session lock (it does not return any messages):

    /**
     * Waits until messages are available. Unless the caller is interrupted, there will be a message available when this
     * method returns.
     */
    public void waitUntilMessagesAvailable() {
      while (unconsumedMessages.isEmpty()) {
        synchronized (unconsumedMessages.getMutex()) {
          try {
            unconsumedMessages.getMutex().wait(2000); // the dispatch channel notifies when a message arrives
          } catch (InterruptedException e) {
            break;
          }
        }
      }
    }

I'll be happy to submit as a patch with associated unit test if there is consensus that this is needed and useful.