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Date: Tue, 30 Mar 2010 06:03:08 +0000 (UTC)
From: "Rob Davies (JIRA)" <jira@apache.org>
To: dev@activemq.apache.org
Subject: [jira] Commented: (AMQ-2679) "VMTransport" NullPointerException
 from ActiveMQSessionExecutor.wakeup
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    [ https://issues.apache.org/activemq/browse/AMQ-2679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=58555#action_58555 ] 

Rob Davies commented on AMQ-2679:
---------------------------------

Does look like it could be a timing issue - can fix in trunk. We don't go back to previous major versions and do releases generally.

> "VMTransport" NullPointerException from ActiveMQSessionExecutor.wakeup
> ----------------------------------------------------------------------
>
>                 Key: AMQ-2679
>                 URL: https://issues.apache.org/activemq/browse/AMQ-2679
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker, Geronimo Integration
>    Affects Versions: 4.1.2
>         Environment: AMQ 4.1.2 embedded in Geronimo 2.1.3, SuSE Linux 11
>            Reporter: TH L.
>
> setup in Geronimo deployment plan with 
> {quote}
> <config-property-setting name="ServerUrl">vm://localhost?async=true&jms.asyncDispatch=false&jms.copyMessageOnSend=false&jms.watchTopicAdvisories=false</config-property-setting> 
> {quote}
> I use only JMS send/reply pattern:
> {quote}
> connection = factory.createQueueConnection(); 
> connection.start(); 
> session = connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE); 
> sender = session.createSender(requestQueue); 
> replyQueue = session.createTemporaryQueue(); 
> jmsRequestMessage = session.createTextMessage(); 
> sender.send(jmsRequestMessage, DeliveryMode.NON_PERSISTENT, Message.DEFAULT_PRIORITY, timeToLive); 
> receiver = session.createReceiver(replyQueue); 
> jmsReplyMessage = receiver.receive(); 
> connection.close();
> {quote}
> When the message traffic get huge (or the server is under intensive computing), I would got such NPE 
> {quote}
>  Exception in thread "VMTransport" java.lang.NullPointerException 
>  at  org.apache.activemq.ActiveMQSessionExecutor.wakeup(ActiveMQSessionExecutor.java:76) 
>  at  org.apache.activemq.ActiveMQSessionExecutor.execute(ActiveMQSessionExecutor.java:61) 
>  at org.apache.activemq.ActiveMQSession.dispatch(ActiveMQSession.java:1344) 
>  at  org.apache.activemq.ActiveMQConnection.onCommand(ActiveMQConnection.java:1485) 
>  at  org.apache.activemq.transport.ResponseCorrelator.onCommand(ResponseCorrelator.java:95) 
>  at  org.apache.activemq.transport.TransportFilter.onCommand(TransportFilter.java:65) 
>  at  org.apache.activemq.transport.vm.VMTransport.iterate(VMTransport.java:201) 
>  at  org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:120) 
>  at  org.apache.activemq.thread.PooledTaskRunner.access$100(PooledTaskRunner.java:26) 
>  at  org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:47) 
>  at  edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:665) 
>  at  edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:690) 
>  at java.lang.Thread.run(Thread.java:619) 
> {quote}
> setting _jms.asyncDispatch=false_ may ease the problem, but the NPE still happens..
> as comment from kevan http://n3.nabble.com/sudden-NullPointerException-from-ActiveMQSessionExecutor-wakeup-tt676485.html#a676966
> It could be a timing hole in ActiveMQSessionExecutor.
> possible fix from kevan
> {quote}
> Index: activemq-core/src/main/java/org/apache/activemq/ActiveMQSessionExecutor.java 
> =================================================================== 
> --- activemq-core/src/main/java/org/apache/activemq/ActiveMQSessionExecutor.java	(revision 663068) 
> +++ activemq-core/src/main/java/org/apache/activemq/ActiveMQSessionExecutor.java	(working copy) 
> @@ -118,10 +118,14 @@ 
>          try { 
>              if (messageQueue.isRunning()) { 
>                  messageQueue.stop(); 
> -                if (taskRunner != null) { 
> -                    taskRunner.shutdown(); 
> -                    taskRunner = null; 
> +                TaskRunner tempTaskRunner; 
> +                synchronized (this) { 
> +                    tempTaskRunner = this.taskRunner; 
> +                    this.taskRunner = null; 
>                  } 
> +                if (tempTaskRunner != null) { 
> +                    tempTaskRunner.shutdown(); 
> +                } 
>              } 
>          } catch (InterruptedException e) { 
>              Thread.currentThread().interrupt(); 
> {quote}

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