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Date: Wed, 15 Feb 2012 21:05:00 +0000 (UTC)
From: "Martin Serrano (Created) (JIRA)" <jira@apache.org>
To: dev@activemq.apache.org
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 <1311388193.42565.1329339900075.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Created] (AMQ-3720) ActiveMqMessageConsumer should have a
 blocking message wait that does not require Session synchronization
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ActiveMqMessageConsumer should have a blocking message wait that does not require Session synchronization
---------------------------------------------------------------------------------------------------------

                 Key: AMQ-3720
                 URL: https://issues.apache.org/jira/browse/AMQ-3720
             Project: ActiveMQ
          Issue Type: Improvement
          Components: JMS client
            Reporter: Martin Serrano
             Fix For: 5.6.0


According to the documentation I've read and response to message [posts|http://activemq.2283324.n4.nabble.com/are-session-commit-and-consumer-receive-allowed-simultaneously-in-separate-threads-tt4387875.html], 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):

{code:java}
    /**
     * 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;
          }
        }
      }
    }
{code}

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

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