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Date: Fri, 8 Apr 2011 04:32:10 -0700 (PDT)
From: dcheckoway <dcheckoway@gmail.com>
To: users@activemq.apache.org
Message-ID: <1302262330227-3435952.post@n4.nabble.com>
Subject: ConcurrentModificationException in embedded 5.5.0 broker
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Hello,

We just migrated from ActiveMQ 5.4.2 to ActiveMQ 5.5.0.  So far so good,
with one exception (pun not intended).  In one case where we have an
embedded broker, we're seeing this exception get logged on occasion:

WARNING; 08-Apr-2011 11:11:41; tid:45931; TransportConnection stopAsync;
cannot create async transport stopper thread.. not waiting for stop to
complete, reason:
java.util.ConcurrentModificationException
        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
        at java.util.HashMap$EntryIterator.next(HashMap.java:834)
        at java.util.HashMap$EntryIterator.next(HashMap.java:832)
        at java.util.HashMap.putAllForCreate(HashMap.java:435)
        at java.util.HashMap.(HashMap.java:225)
        at
org.slf4j.helpers.BasicMDCAdapter.getCopyOfContextMap(BasicMDCAdapter.java:130)
        at org.slf4j.MDC.getCopyOfContextMap(MDC.java:182)
        at
org.apache.activemq.util.MDCHelper.getCopyOfContextMap(MDCHelper.java:30)
        at
org.apache.activemq.broker.TransportConnection.stopAsync(TransportConnection.java:946)
        at
org.apache.activemq.broker.TransportConnection.processShutdown(TransportConnection.java:353)
        at
org.apache.activemq.command.ShutdownInfo.visit(ShutdownInfo.java:35)
        at
org.apache.activemq.broker.TransportConnection.service(TransportConnection.java:306)
        at
org.apache.activemq.broker.TransportConnection$1.onCommand(TransportConnection.java:179)
        at
org.apache.activemq.transport.ResponseCorrelator.onCommand(ResponseCorrelator.java:116)
        at
org.apache.activemq.transport.TransportFilter.onCommand(TransportFilter.java:69)
        at
org.apache.activemq.transport.vm.VMTransport.iterate(VMTransport.java:218)
        at
org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:127)
        at
org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:48)
        at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662)

Up until this morning, I had only seen that logged during shutdown of the
app context.  But just now, it popped out independently, out of the blue.

For what it's worth, here's the app context config:

  
  
    
      
        
          " producerFlowControl="false" memoryLimit="20mb"/>
        
      
    
    
      
    
  

Has anybody else seen this ConcurrentModificationException happening with
5.5.0 (or otherwise)?  Any ideas?

-----
Dan Checkoway
dcheckoway gmail com
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