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https://issues.apache.org/jira/browse/MAPREDUCE-995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756466#action_12756466
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Hong Tang commented on MAPREDUCE-995:
-------------------------------------
I found this issue while preparing patch for Mumak (Hadoop Simulator
MAPREDUCE-728). The backtrace of the problem is as follows:
{noformat}
java.lang.NullPointerException
at
org.codehaus.jackson.impl.WriterBasedGenerator._verifyValueWrite(WriterBasedGenerator.java:553)
at
org.codehaus.jackson.impl.JsonGeneratorBase.writeStartObject(JsonGeneratorBase.java:142)
at
org.apache.hadoop.mapreduce.jobhistory.EventWriter.writeEventType(EventWriter.java:81)
at
org.apache.hadoop.mapreduce.jobhistory.EventWriter.write(EventWriter.java:60)
at
org.apache.hadoop.mapreduce.jobhistory.JobHistory.logEvent(JobHistory.java:339)
at
org.apache.hadoop.mapred.JobInProgress.completedTask(JobInProgress.java:2519)
at
org.apache.hadoop.mapred.JobInProgress.updateTaskStatus(JobInProgress.java:1130)
at
org.apache.hadoop.mapred.SimulatorJobTracker.updateTaskStatuses(SimulatorJobTracker.java:621)
{noformat}
The last statement in the backtrace occurs in the context when the job has
failed (one task fails 4 times), and the job is marked as complete. Then a
lingering task that belongs to the same job completes, and JT tries to update
its status.
> JobHistory should handle cases where task completion events are generated
> after job completion event
> ----------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-995
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-995
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Jothi Padmanabhan
> Assignee: Jothi Padmanabhan
>
> It is apparently possible, in certain circumstances (failed job, for
> example), for the job history to get task completion events after the job
> completion event. This currently causes NPE in job history.
> Thanks Hong for identifying this issue
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