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From Sameer Joshi <sameer.jo...@serenesoftware.com>
Subject Re: java.lang.NullPointerException at java.util.concurrent.ConcurrentHashMap
Date Wed, 28 Jul 2010 17:08:42 GMT
Hi Sonal,
Thank you for replying.

I'm trying to run it as single node, so I had localhost in all the conf
files and in /etc/hosts. I tried replacing it with 127.0.0.1 in all Hadoop
conf files (read to do that on some forum), but with no change.

I figured I didn't need hostname since I was trying to run it locally, but
still tried replacing localhost with 173.1.86.194. However, as expected, it
could not connect to server.

Any thoughts?

Thanks for your help, I'm new at this and feel much obliged.

Regards,
Sameer

On Wed, Jul 28, 2010 at 12:12 AM, Sonal Goyal <sonalgoyal4@gmail.com> wrote:

> 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.
> >
>



-- 
Dr. Sameer Joshi, Ph.D.
Senior computer scientist,
Serene Software.

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