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https://issues.apache.org/jira/browse/MAPREDUCE-2470?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13036811#comment-13036811
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Robert Joseph Evans commented on MAPREDUCE-2470:
------------------------------------------------
The difference is that with Job.getStatus it calls internally updateStatus
which will throw an IOException if it is unable to get an updated status from
the JobTracker. The only time you can get an NPE from that is if you catch the
IOException, ignore it, and keep trying to use the Job object what was
originally created. We can fix that, by modifying updateStatus to not
overwrite Job.status until it knows that the updated status is not null. But
that was not explicitly part of this JIRA, and I could not find any other JIRA
to cover it so I though it was not a big deal, and most likely worked as
designed.
> Receiving NPE occasionally on RunningJob.getCounters() call
> -----------------------------------------------------------
>
> Key: MAPREDUCE-2470
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2470
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: client
> Affects Versions: 0.21.0
> Environment: FreeBSD, Java6, Hadoop r0.21.0
> Reporter: Aaron Baff
> Assignee: Robert Joseph Evans
> Attachments: MAPREDUCE-2470-v1.patch, MAPREDUCE-2470-v2.patch,
> counters_null_data.pcap
>
>
> This is running in a Java daemon that is used as an interface (Thrift) to get
> information and data from MR Jobs. Using JobClient.getJob(JobID) I
> successfully get a RunningJob object (I'm checking for NULL), and then rarely
> I get an NPE when I do RunningJob.getCounters(). This seems to occur after
> the daemon has been up and running for a while, and in the event of an
> Exception, I close the JobClient, set it to NULL, and a new one should then
> be created on the next request for data. Yet, I still seem to be unable to
> fetch the Counters. Below is the stack trace.
> java.lang.NullPointerException
> at org.apache.hadoop.mapred.Counters.downgrade(Counters.java:77)
> at
> org.apache.hadoop.mapred.JobClient$NetworkedJob.getCounters(JobClient.java:381)
> at
> com.telescope.HadoopThrift.service.ServiceImpl.getReportResults(ServiceImpl.java:350)
> at
> com.telescope.HadoopThrift.gen.HadoopThrift$Processor$getReportResults.process(HadoopThrift.java:545)
> at
> com.telescope.HadoopThrift.gen.HadoopThrift$Processor.process(HadoopThrift.java:421)
> at
> org.apache.thrift.server.TNonblockingServer$FrameBuffer.invoke(TNonblockingServer.java:697)
> at
> org.apache.thrift.server.THsHaServer$Invocation.run(THsHaServer.java:317)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:619)
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