NullPoinerEcxeption while running HBase MapReduce Job

Question

I was trying to run an HBase Mapreduce Job in hadoop. I use ${HADOOP_HOME}/bin/hadoop jar ${HBASE_HOME}/lib/hbase-server-VERSION.jar rowcounter usertable for running job.

While running I am getting following exception

Exception in thread "main" java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.hbase.mapreduce.Driver.main(Driver.java:54)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:212)
Caused by: java.lang.NullPointerException
        at org.apache.hadoop.net.DNS.reverseDns(DNS.java:92)
        at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.reverseDNS(TableInputFormatBase.java:228)
        at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.getSplits(TableInputFormatBase.java:191)
        at org.apache.hadoop.mapreduce.JobSubmitter.writeNewSplits(JobSubmitter.java:493)
        at org.apache.hadoop.mapreduce.JobSubmitter.writeSplits(JobSubmitter.java:510)
        at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:394)
        at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1285)
        at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1282)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:396)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1614)
        at org.apache.hadoop.mapreduce.Job.submit(Job.java:1282)
        at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1303)
        at org.apache.hadoop.hbase.mapreduce.RowCounter.main(RowCounter.java:191)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:72)
        at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:145)
        at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:153)
        ... 10 more

Can anybody explain why this NullPointerException is throwing

Answer 1

Caused by: java.lang.NullPointerException
        at org.apache.hadoop.net.DNS.reverseDns(DNS.java:92)
        at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.reverseDNS(TableInputFormatBase.java:228)
        at org.apache.hadoop.hbase.mapreduce.TableInputFormatBase.getSplits(TableInputFormatBase.java:191)

As per the above exception, it seems like there is some problem in doing Reversedns lookup. This hints that there is an infrstructure/network/os setup problem.

Answer 2

The reverse DNS isn't working maybe because your router isn't doing it's job. An easy fix is to edit your /etc/hosts and put an entry for you servers. I'm running on my laptop so only need one entry:

#reverse DNS for home LAN
192.168.0.2
maclaurin.local maclaurin

You'd need to set this for each machine in your cluster but make sure to add in don't replace your /etc/hosts.

Note : This works on one LAN with static addresses only. Go to another location and this may cause the router reverse DNS to fail because /etc/hosts takes precedence over any other lookup. I set my home router to give a reserved address to my laptop to match my other location so it works between the two. Just be aware that changes to /etc/hosts are problematic sometimes when moving locations.