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Amareshwari Sriramadasu commented on MAPREDUCE-1372: ---------------------------------------------------- bq. Node resolution through heartbeat(JT.addNewTracker) also need to wait for the thread, right? Discussed this with Arun. We can have node resolution through heartbeat inline (as it is now). Make node resolution for JobInProgress go thru the Thread. > ConcurrentModificationException in JobInProgress > ------------------------------------------------ > > Key: MAPREDUCE-1372 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-1372 > Project: Hadoop Map/Reduce > Issue Type: Bug > Components: jobtracker > Affects Versions: 0.20.1 > Reporter: Amareshwari Sriramadasu > Priority: Blocker > Fix For: 0.21.0 > > Attachments: M1372-0.patch > > > We have seen the following ConcurrentModificationException in one of our > clusters > {noformat} > java.io.IOException: java.util.ConcurrentModificationException > at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793) > at java.util.HashMap$KeyIterator.next(HashMap.java:828) > at > org.apache.hadoop.mapred.JobInProgress.findNewMapTask(JobInProgress.java:2018) > at > org.apache.hadoop.mapred.JobInProgress.obtainNewMapTask(JobInProgress.java:1077) > at > org.apache.hadoop.mapred.CapacityTaskScheduler$MapSchedulingMgr.obtainNewTask(CapacityTaskScheduler.java:796) > at > org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.getTaskFromQueue(CapacityTaskScheduler.java:589) > at > org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.assignTasks(CapacityTaskScheduler.java:677) > at > org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.access$500(CapacityTaskScheduler.java:348) > at > org.apache.hadoop.mapred.CapacityTaskScheduler.addMapTask(CapacityTaskScheduler.java:1397) > at > org.apache.hadoop.mapred.CapacityTaskScheduler.assignTasks(CapacityTaskScheduler.java:1349) > at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:2976) > at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) > at java.lang.reflect.Method.invoke(Method.java:597) > at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:508) > at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:959) > at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:955) > at java.security.AccessController.doPrivileged(Native Method) > at javax.security.auth.Subject.doAs(Subject.java:396) > at org.apache.hadoop.ipc.Server$Handler.run(Server.java:953) > {noformat} -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.