Error in IsolationRunner - java.lang.NullPointerException

[jingzhongxu <ji...@zju.edu.cn>]

hi

I am using the CDH3u1 stack.when I use IsolationRunner to remote debug code,I encounter the following errors,
Exception in thread "main" java.lang.NullPointerException
        at org.apache.hadoop.fs.LocalDirAllocator$AllocatorPerContext.ifExists(LocalDirAllocator.java:502)
        at org.apache.hadoop.fs.LocalDirAllocator.ifExists(LocalDirAllocator.java:216)
        at org.apache.hadoop.mapred.IsolationRunner.run(IsolationRunner.java:195)
        at org.apache.hadoop.mapred.IsolationRunner.main(IsolationRunner.java:238)
        
In general,The task attempt directory is in the following location: 
mapred.local.dir/taskTracker/jobcache/job-ID/task-attempt-ID.
but when i log into the node that the task failed on and look for the directory for that task attempt,but 
i found my directory is in the following location:
mapred.local.dir/taskTracker/user-id/jobcache/job-ID/task-attempt-ID,
and i don't find work directory.The work directory is in the job-ID directory and is empty.
my steps is as follows:
first,set some options to allow the remote debugger to connect,then the IsolationRunner is launched with the following command:
/bin/hadoop org.apache.hadoop.mapred.IsolationRunner /home/hadoop/cloudera-data/mapred/local/taskTracker/jingzhongxu/jobcache/job_201109130027_0002/attempt_201109130027_0002_m_000000_0/job.xml jingzhongxu

thanks !
jingzhongxu