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