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https://issues.apache.org/jira/browse/HADOOP-5198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12674139#action_12674139
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Amareshwari Sriramadasu commented on HADOOP-5198:
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bq. Can pid become null between where you check for it and where you call
ProcessTree.destroy(...)?
No. pid cannnot become null. Once obtained from the file, it is stored in a
String and passed to the kill-process.
bq. Can you write a unit test? If not, can you describe the steps of the manual
testing you did to ensure this patch works?
This is almost all the time reproducible by running MRReliability test on
single-node cluster and occasional failures on cluster. I didnt see any failure
after the patch.
> NPE in Shell.runCommand()
> -------------------------
>
> Key: HADOOP-5198
> URL: https://issues.apache.org/jira/browse/HADOOP-5198
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred, util
> Affects Versions: 0.21.0
> Reporter: Amareshwari Sriramadasu
> Assignee: Amareshwari Sriramadasu
> Fix For: 0.21.0
>
> Attachments: patch-5198.txt
>
> Original Estimate: 0h
> Remaining Estimate: 0h
>
> I have seen one of the task failures with following exception:
> java.lang.NullPointerException
> at java.lang.ProcessBuilder.start(ProcessBuilder.java:441)
> at org.apache.hadoop.util.Shell.runCommand(Shell.java:149)
> at org.apache.hadoop.util.Shell.run(Shell.java:134)
> at
> org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:286)
> at org.apache.hadoop.util.ProcessTree.isAlive(ProcessTree.java:244)
> at
> org.apache.hadoop.util.ProcessTree.sigKillInCurrentThread(ProcessTree.java:67)
> at org.apache.hadoop.util.ProcessTree.sigKill(ProcessTree.java:115)
> at
> org.apache.hadoop.util.ProcessTree.destroyProcessGroup(ProcessTree.java:164)
> at org.apache.hadoop.util.ProcessTree.destroy(ProcessTree.java:180)
> at
> org.apache.hadoop.mapred.JvmManager$JvmManagerForType$JvmRunner.kill(JvmManager.java:377)
> at
> org.apache.hadoop.mapred.JvmManager$JvmManagerForType.reapJvm(JvmManager.java:249)
> at
> org.apache.hadoop.mapred.JvmManager$JvmManagerForType.access$000(JvmManager.java:113)
> at org.apache.hadoop.mapred.JvmManager.launchJvm(JvmManager.java:76)
> at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:411)
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