Hi, It seems like you trying to run only the reducer without a mapper. Can you share main() method code which you trying to run?
On Mon, Jan 23, 2012 at 11:43 AM, burakkk <burak.isi...@gmail.com> wrote: > 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 > -- Join me at http://hadoopworkshop.eventbrite.com/
