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From Sonal Goyal <sonalgoy...@gmail.com>
Subject Re: java.lang.NullPointerException at java.util.concurrent.ConcurrentHashMap
Date Wed, 28 Jul 2010 04:12:26 GMT
Hi Sameer,

For GoGrid, you will have to configure /etc/hosts with the ip and hostname
for master and slaves. If you run hostname and nslookup -sil, you will get
the details for your machines. Make sure /etc/hosts has an entry like:

173.1.45.202 173.1.45.202.reverse.gogrid.com 28684_1_85017_358406

Thanks and Regards,
Sonal
www.meghsoft.com
http://in.linkedin.com/in/sonalgoyal


On Wed, Jul 28, 2010 at 6:42 AM, Sameer Joshi <
sameer.joshi@serenesoftware.com> wrote:

> I installed Java and Hadoop on a GoGrid cloud server using Red Hat
> Enterprise Linux Server release 5.1 (Tikanga). Hadoop installed fine and
> starts fine, however I get an error (java.lang.NullPointerException at
> java.util.concurrent.ConcurrentHashMap) while running the Hadoop wordcount
> example. My guess was that this was a localhost or IPv6 issue.
>
> * I have tested replacing 'localhost' with both the local IP, and server IP
> addresses (when out of options) in Hadoop conf
> * I have disabled IPv6 both in sysctl.conf and hadoop-env.sh (former
> followed by a server restart)
>
> Any thoughts?
> Thank you.
>
>
> The output is given below
>
> # bin/hadoop jar hadoop-0.20.2-examples.jar wordcount datasets tests/out7
> 10/07/27 05:44:59 INFO input.FileInputFormat: Total input paths to process
> :
> 1
> 10/07/27 05:44:59 INFO mapred.JobClient: Running job: job_201007270544_0001
> 10/07/27 05:45:00 INFO mapred.JobClient: map 0% reduce 0%
> 10/07/27 05:45:12 INFO mapred.JobClient: map 100% reduce 0%
> 10/07/27 05:45:17 INFO mapred.JobClient: Task Id :
> attempt_201007270544_0001_r_000000_0, Status : FAILED
>
> Error: java.lang.NullPointerException
> at java.util.concurrent.ConcurrentHashMap.get(Unknown Source)
> at
>
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
>
> at
>
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
>
>
> 10/07/27 05:45:24 INFO mapred.JobClient: Task Id :
> attempt_201007270544_0001_r_000000_1, Status : FAILED
> Error: java.lang.NullPointerException
> at java.util.concurrent.ConcurrentHashMap.get(Unknown Source)
> at
>
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
>
> at
>
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
>
>
> 10/07/27 05:45:30 INFO mapred.JobClient: Task Id :
> attempt_201007270544_0001_r_000000_2, Status : FAILED
> Error: java.lang.NullPointerException
> at java.util.concurrent.ConcurrentHashMap.get(Unknown Source)
> at
>
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
>
> at
>
> org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
>
>
> 10/07/27 05:45:39 INFO mapred.JobClient: Job complete:
> job_201007270544_0001
>
> 10/07/27 05:45:39 INFO mapred.JobClient: Counters: 12
> 10/07/27 05:45:39 INFO mapred.JobClient: Job Counters
> 10/07/27 05:45:39 INFO mapred.JobClient: Launched reduce tasks=4
> 10/07/27 05:45:39 INFO mapred.JobClient: Launched map tasks=1
> 10/07/27 05:45:39 INFO mapred.JobClient: Data-local map tasks=1
> 10/07/27 05:45:39 INFO mapred.JobClient: Failed reduce tasks=1
> 10/07/27 05:45:39 INFO mapred.JobClient: FileSystemCounters
> 10/07/27 05:45:39 INFO mapred.JobClient: HDFS_BYTES_READ=15319
> 10/07/27 05:45:39 INFO mapred.JobClient: FILE_BYTES_WRITTEN=12847
> 10/07/27 05:45:39 INFO mapred.JobClient: Map-Reduce Framework
> 10/07/27 05:45:39 INFO mapred.JobClient: Combine output records=934
> 10/07/27 05:45:39 INFO mapred.JobClient: Map input records=149
> 10/07/27 05:45:39 INFO mapred.JobClient: Spilled Records=934
> 10/07/27 05:45:39 INFO mapred.JobClient: Map output bytes=25346
> 10/07/27 05:45:39 INFO mapred.JobClient: Combine input records=2541
> 10/07/27 05:45:39 INFO mapred.JobClient: Map output records=2541
>
> --
> Dr. Sameer Joshi, Ph.D.
> Senior computer scientist,
> Serene Software.
>

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