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From "bhushan.kandalkar" <bhushan.kandal...@harbingergroup.com>
Subject Re: MapReduce job over HBase fails
Date Wed, 27 Feb 2013 04:33:42 GMT

Hi Nick, 

Error log: 
								Exception in thread "main" java.lang.NullPointerException 
 at org.apache.hadoop.net.DNS.reverseDns(DNS.java:72) 
 at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.reverseDNS(TableInputFormatBase.java:218)

 at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.getSplits(TableInputFormatBase.java:183)

 at org.apache.hadoop.mapred.JobClient.writeNewSplits(JobClient.java:962) 
 at org.apache.hadoop.mapred.JobClient.writeSplits(JobClient.java:979) 
 at org.apache.hadoop.mapred.JobClient.access$600(JobClient.java:174) 
 at org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:897) 
 at org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:850) 
 at java.security.AccessController.doPrivileged(Native Method) 
 at javax.security.auth.Subject.doAs(Subject.java:416) 
 at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1121) 
 at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:850) 
 at org.apache.hadoop.mapreduce.Job.submit(Job.java:500) 
 at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:530) 
 at org.apache.hadoop.hbase.mapreduce.CopyTable.main(CopyTable.java:237) 
How to resolve it? Is it related to HBASE-7693? 
Thanks, Bhushan 
							On Wed 27/02/13  1:26 AM , "Nick Dimiduk [via Apache HBase]" ml-node s679495n4039235h34@n3.nabble.com
To: ml-node s679495n4039235h34@n3.nabble.com 	Hi Bhushan, 

Yes, MapReduce is supported over HBase for all releases in recent memory. 

Please provide the relevant stacktrace of the error you're seeing. How are 
you interacting with HBase from MapReduce -- for online reading, writing, I 
recommend you make use of TableMapper, TableReducer. Be sure to configure 
your job using TableMapReduceUtil. All of these classes, along with 
examples of writing MapReduce jobs against HBase, are shipped in the 
org.apache.hadoop.hbase.mapreduce package. 

Are you able to interact with HBase via the shell (create table, put, 
scan)? Be sure you've satisfied the prerequisites [0] for running HBase. 
Specifically, I suspect DNS [1] and loopback [2] configuration 
are pertinent. 


[0]: http://hbase.apache.org/book.html#basic.prerequisites 
[1]: http://hbase.apache.org/book.html#dns 
[2]: http://hbase.apache.org/book.html#loopback.ip 

On Sun, Feb 24, 2013 at 8:57 PM, bhushan.kandalkar &lt; 
[hidden email] &gt; wrote: 

&gt; Thanks Ted. 
&gt; I am using Hadoop-1.0.3 and HBase-0.94.3. Is MapReduce job runs over this 
&gt; configuration? 
&gt; -- 
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