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From Sameer Joshi <sameer.jo...@serenesoftware.com>
Subject Re: java.lang.NullPointerException at java.util.concurrent.ConcurrentHashMap
Date Sun, 01 Aug 2010 02:05:10 GMT
Hi again Sonal,
Just checking, if I'm running a pseudo-cluster on one node, so the master
and slaves are all localhost. What may the /etc/hosts look like in this
case?

Thanks,
Sameer

On Sat, Jul 31, 2010 at 3:37 AM, Sameer Joshi <
sameer.joshi@serenesoftware.com> wrote:

> Hi Sonal,
> Sorry for the late reply, I was traveling. The logs, unfortunately, did not
> yield too much information. I'll try some more configurations with etc/hosts
> edits, and see if I can't get it to behave.
> Thanks so much again for your help.
> Sameer
>
>
> On Wed, Jul 28, 2010 at 1:20 PM, Sonal Goyal <sonalgoyal4@gmail.com>wrote:
>
>> Hi Sameer,
>>
>> Do you see all processes up? Can you check the logs and see what is going
>> wrong? I suspect you will need to make the entries in /etc/hosts anyways.
>> Somewhere in hadoop code, the ip  hostname mapping is done, I forget the
>> exact location.
>>
>> Thanks and Regards,
>> Sonal
>> www.meghsoft.com
>> http://in.linkedin.com/in/sonalgoyal
>>
>>
>> On Wed, Jul 28, 2010 at 10:38 PM, Sameer Joshi <
>> sameer.joshi@serenesoftware.com> wrote:
>>
>> > 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.
>> >
>>
>
>
>
> --
> Dr. Sameer Joshi, Ph.D.
> Senior computer scientist,
> Serene Software.
>
>


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

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