Hello everyone,
I have 3 server(1 master, 2 slave) and I installed cdh3u2 on each
server. I execute simple wordcount example but reducer had a
NullPointerException. How can i solve this problem?
The error log is that:
Error: java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:
768)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2806)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.run(ReduceTask.java:2733)
Error: java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:
768)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2806)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.run(ReduceTask.java:2733)
Error: java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:
768)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2806)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.run(ReduceTask.java:2733)
Error: java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:
768)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2806)
at org.apache.hadoop.mapred.ReduceTask$ReduceCopier
$GetMapEventsThread.run(ReduceTask.java:2733)
Thanks
Best Regards
