nageswara Rao [https://community.jboss.org/people/itsnagesh] created the discussion "Concurrent Modification exception in task server when running with 100 concurrent users" To view the discussion, visit: https://community.jboss.org/message/790471#790471 -------------------------------------------------------------- I have a business process with 5 manual activities with a fork, initially all user tasks are assigned to business admin My scenario is like start process instance for this Process,  then business admin deligate each task to a seperate user and that user will complete the task then next task will be created When i execute this scenario with 100 concurrent users in load runner then 2% of the markdone operations are failing with Concurrent modifcation exception [java] java.util.ConcurrentModificationException      [java]  at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)      [java]  at java.util.AbstractList$Itr.next(AbstractList.java:343)      [java]  at org.jbpm.task.event.MessagingTaskEventListener.taskCompleted(MessagingTaskEventListener.java:72)      [java]  at org.jbpm.task.event.TaskEventSupport.fireTaskCompleted(TaskEventSupport.java:47)      [java]  at org.jbpm.task.service.TaskServiceSession.postTaskCompleteOperation(TaskServiceSession.java:497)      [java]  at org.jbpm.task.service.TaskServiceSession.taskOperation(TaskServiceSession.java:463)      [java]  at org.jbpm.task.service.TaskServerHandler.messageReceived(TaskServerHandler.java:84)      [java]  at org.jbpm.task.service.mina.MinaTaskServerHandler.messageReceived(MinaTaskServerHandler.java:41)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.messageReceived(DefaultIoFilterChain.java:716)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:796)      [java]  at org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolDecoderOutputImpl.flush(ProtocolCodecFilter.java:427)      [java]  at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:245)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:796)      [java]  at org.apache.mina.filter.logging.LoggingFilter.messageReceived(LoggingFilter.java:177)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:46)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:796)      [java]  at org.apache.mina.core.filterchain.IoFilterAdapter.messageReceived(IoFilterAdapter.java:119)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)      [java]  at org.apache.mina.core.filterchain.DefaultIoFilterChain.fireMessageReceived(DefaultIoFilterChain.java:426)      [java]  at org.apache.mina.core.polling.AbstractPollingIoProcessor.read(AbstractPollingIoProcessor.java:692)      [java]  at org.apache.mina.core.polling.AbstractPollingIoProcessor.process(AbstractPollingIoProcessor.java:645)      [java]  at org.apache.mina.core.polling.AbstractPollingIoProcessor.process(AbstractPollingIoProcessor.java:634)      [java]  at org.apache.mina.core.polling.AbstractPollingIoProcessor.access$400(AbstractPollingIoProcessor.java:66)      [java]  at org.apache.mina.core.polling.AbstractPollingIoProcessor$Processor.run(AbstractPollingIoProcessor.java:1078)      [java]  at org.apache.mina.util.NamePreservingRunnable.run(NamePreservingRunnable.java:64)      [java]  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)      [java]  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)      [java]  at java.lang.Thread.run(Thread.java:662) -------------------------------------------------------------- Reply to this message by going to Community [https://community.jboss.org/message/790471#790471] Start a new discussion in jBPM at Community [https://community.jboss.org/choose-container!input.jspa?contentType=1&...]