Dear All,
Please help with the NullPointerException in the WordCount example. Sorry it’s
the simple code because I am new to hadoop. :-)
I am running v0.20.1 in Ubuntu 9.10. The map task works perfectly. But there
is NPE with the reduce task. Is there anything wrong with the configuration or
the Reduce.java code?
Below are the error messages from job tracker, and the attached are the source
code. Thank you so much!
Error: java.lang.NullPointerException
at
java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
Error: java.lang.NullPointerException
at
java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
Error: java.lang.NullPointerException
at
java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
Error: java.lang.NullPointerException
at
java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
- Frank
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