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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3590) Null pointer exception in JobTracker when the task tracker is not yet resolved
Date Wed, 18 Jun 2008 04:30:44 GMT
Null pointer exception in JobTracker when the task tracker is not yet resolved

                 Key: HADOOP-3590
                 URL: https://issues.apache.org/jira/browse/HADOOP-3590
             Project: Hadoop Core
          Issue Type: Bug
          Components: mapred
            Reporter: Amar Kamat
            Assignee: Amar Kamat
            Priority: Blocker
             Fix For: 0.18.0

2008-06-17 13:29:56,711 INFO org.apache.hadoop.mapred.JobTracker: Got heartbeat from: xxx
(initialContact: false acceptNewTasks: true) with responseId: 0
2008-06-17 13:29:56,711 INFO org.apache.hadoop.ipc.Server: IPC Server handler 7 on 123, call
heartbeat(org.apache.hadoop.mapred.TaskTrackerStatus@123, true, true, -1) from xxx error:
java.io.IOException: java.lang.NullPointerException
java.io.IOException: java.lang.NullPointerException
       at org.apache.hadoop.mapred.JobTracker.getParentNode(JobTracker.java:1327)
       at org.apache.hadoop.mapred.JobInProgress.findNewMapTask(JobInProgress.java:1142)
       at org.apache.hadoop.mapred.JobInProgress.obtainNewMapTask(JobInProgress.java:685)
       at org.apache.hadoop.mapred.JobTracker.getNewTaskForTaskTracker(JobTracker.java:1708)
       at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:1431)
       at sun.reflect.GeneratedMethodAccessor2.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$Server.call(RPC.java:452)
       at org.apache.hadoop.ipc.Server$Handler.run(Server.java:888)
Looks like a corner case. This happens when the task tracker just joins the JT and asks for
a task to run. In a case where the task tracker is not yet resolved, this can lead to null
pointer exception. Remember that the task trackers are  added to separate queue and resolved
by a separate thread i.e there is no forced resolution for task trackers. There is no side
effect of this bug since the task tracker will try again and also the job runs to completion.

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