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https://issues.apache.org/jira/browse/MAPREDUCE-6852?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15889206#comment-15889206
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Jian He commented on MAPREDUCE-6852:
------------------------------------
looks like getJobID is used in the same class in several other places, we may
just use this method.
> Job#updateStatus() failed with NPE due to race condition
> --------------------------------------------------------
>
> Key: MAPREDUCE-6852
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6852
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Junping Du
> Assignee: Junping Du
> Attachments: MAPREDUCE-6852.patch
>
>
> Like MAPREDUCE-6762, we found this issue in a cluster where Pig query
> occasionally failed on NPE - "Pig uses JobControl API to track MR job status,
> but sometimes Job History Server failed to flush job meta files to HDFS which
> caused the status update failed." Beside NPE in
> o.a.h.mapreduce.Job.getJobName, we also get NPE in Job.updateStatus() and the
> exception is as following:
> {noformat}
> Caused by: java.lang.NullPointerException
> at org.apache.hadoop.mapreduce.Job$1.run(Job.java:323)
> at org.apache.hadoop.mapreduce.Job$1.run(Job.java:320)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:422)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1833)
> at org.apache.hadoop.mapreduce.Job.updateStatus(Job.java:320)
> at org.apache.hadoop.mapreduce.Job.isComplete(Job.java:604)
> {noformat}
> We found state here is null. However, we already check the job state to be
> RUNNING as code below:
> {noformat}
> public boolean isComplete() throws IOException {
> ensureState(JobState.RUNNING);
> updateStatus();
> return status.isJobComplete();
> }
> {noformat}
> The only possible reason here is two threads are calling here for the same
> time: ensure state first, then one thread update the state to null while the
> other thread hit NPE issue here.
> We should fix this NPE exception.
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