Kahadb永続メッセージングを備えたAMQ5.6でAMQメッセージグループを使用しており、ログにこの警告が定期的に表示されます。これに起因する特定のエラーは見当たりませんが、これの副作用は何であるかなど疑問に思っています。
私のコンシューマーは、maxConcurrentConsumers = 5のCamel（2.9.2）ルートです（AMQ接続プールなどを使用）。ある時点でこれを単体テストに要約してみます...今のところ、ここにスタックトレースがあります
Async error occurred: java.util.concurrent.ExecutionException: java.util.ConcurrentModificationException
java.util.concurrent.ExecutionException: java.util.ConcurrentModificationException
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
at java.util.concurrent.FutureTask.get(FutureTask.java:83)
at org.apache.activemq.broker.region.Queue.doMessageSend(Queue.java:785)
at org.apache.activemq.broker.region.Queue.send(Queue.java:707)
at org.apache.activemq.broker.region.AbstractRegion.send(AbstractRegion.java:407)
at org.apache.activemq.broker.region.RegionBroker.send(RegionBroker.java:503)
at org.apache.activemq.broker.jmx.ManagedRegionBroker.send(ManagedRegionBroker.java:305)
at org.apache.activemq.broker.BrokerFilter.send(BrokerFilter.java:129)
at org.apache.activemq.broker.CompositeDestinationBroker.send(CompositeDestinationBroker.java:96)
at org.apache.activemq.broker.TransactionBroker.send(TransactionBroker.java:306)
at org.apache.activemq.broker.MutableBrokerFilter.send(MutableBrokerFilter.java:135)
at org.apache.activemq.broker.TransportConnection.processMessage(TransportConnection.java:453)
at org.apache.activemq.command.ActiveMQMessage.visit(ActiveMQMessage.java:681)
at org.apache.activemq.broker.TransportConnection.service(TransportConnection.java:292)
at org.apache.activemq.broker.TransportConnection$1.onCommand(TransportConnection.java:150)
at org.apache.activemq.transport.ResponseCorrelator.onCommand(ResponseCorrelator.java:116)
at org.apache.activemq.transport.MutexTransport.onCommand(MutexTransport.java:50)
at org.apache.activemq.transport.vm.VMTransport.iterate(VMTransport.java:231)
at org.apache.activemq.thread.PooledTaskRunner.runTask(PooledTaskRunner.java:122)
at org.apache.activemq.thread.PooledTaskRunner$1.run(PooledTaskRunner.java:43)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
Caused by: java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$KeyIterator.next(HashMap.java:828)
at org.apache.activemq.util.MarshallingSupport.marshalPrimitiveMap(MarshallingSupport.java:64)
at org.apache.activemq.command.Message.beforeMarshall(Message.java:210)
at org.apache.activemq.command.ActiveMQObjectMessage.beforeMarshall(ActiveMQObjectMessage.java:199)
at org.apache.activemq.openwire.v6.MessageMarshaller.looseMarshal(MessageMarshaller.java:277)
at org.apache.activemq.openwire.v6.ActiveMQMessageMarshaller.looseMarshal(ActiveMQMessageMarshaller.java:111)
at org.apache.activemq.openwire.v6.ActiveMQObjectMessageMarshaller.looseMarshal(ActiveMQObjectMessageMarshaller.java:111)
at org.apache.activemq.openwire.OpenWireFormat.marshal(OpenWireFormat.java:168)
at org.apache.activemq.store.kahadb.KahaDBStore$KahaDBMessageStore.addMessage(KahaDBStore.java:429)
at org.apache.activemq.store.kahadb.KahaDBStore$StoreQueueTask.run(KahaDBStore.java:1177)