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From madhu phatak <phatak....@gmail.com>
Subject Re: Reducer NullPointerException
Date Fri, 02 Mar 2012 05:19:07 GMT
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.isikli@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
>



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