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https://issues.apache.org/jira/browse/HADOOP-1171?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12493992
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Tahir Hashmi commented on HADOOP-1171:
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I went through the code for to figure out why the NPE might have been
triggered. It seems like jobHasFinished() might have issues with
synchronisation. There are concurrent threads calling on this function and
there's one call to TaskInProgress.cleanup() which removes TIPs from the tasks
map and is not synchronised.
There may be a race condition when two threads try to cleanup() the same TIP.
Need someone who's familiar with this code to comment on it.
> NPE in TaskTracker RenitTrackerAction
> --------------------------------------
>
> Key: HADOOP-1171
> URL: https://issues.apache.org/jira/browse/HADOOP-1171
> Project: Hadoop
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.12.1
> Reporter: Koji Noguchi
> Assigned To: Tahir Hashmi
>
> TaskTracker log shows =============
> 2007-03-28 02:32:18,076 INFO org.apache.hadoop.mapred.TaskTracker: Recieved
> RenitTrackerAction from JobTracker
> 2007-03-28 02:32:18,494 ERROR org.apache.hadoop.mapred.TaskTracker: Can not
> start task tracker because java.lang.NullPointerException
> at
> org.apache.hadoop.mapred.TaskTracker$TaskInProgress.jobHasFinished(TaskTracker.java:1187)
> at org.apache.hadoop.mapred.TaskTracker.close(TaskTracker.java:430)
> at org.apache.hadoop.mapred.TaskTracker.run(TaskTracker.java:917)
> at org.apache.hadoop.mapred.TaskTracker.main(TaskTracker.java:1589)
> JobTracker log shows ==============
> 2007-03-28 02:31:18,977 INFO org.apache.hadoop.mapred.JobTracker: Lost
> tracker '____.____.com'
> ...
> 2007-03-28 02:31:18,977 INFO org.apache.hadoop.mapred.JobInProgress:
> TaskTracker at 'tracker____.___.com' turned 'flaky'
> ...
> 2007-03-28 02:32:18,075 WARN org.apache.hadoop.mapred.JobTracker: Status from
> unknown Tracker : tracker____.___.com:#####
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