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Posted to mapreduce-issues@hadoop.apache.org by "Suraj Menon (JIRA)" <ji...@apache.org> on 2011/08/12 22:55:27 UTC
[jira] [Commented] (MAPREDUCE-2097) java.lang.NullPointerException
in reduce task
[ https://issues.apache.org/jira/browse/MAPREDUCE-2097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13084371#comment-13084371 ]
Suraj Menon commented on MAPREDUCE-2097:
----------------------------------------
Hello,
I faced a similar error. Found out that it is causing for me because of '=' sign in my hostname.
As an example, please read the following snippet:
URI u = URI.create("http://abcd--proto=dhcp:5006");
String host = u.getHost();
System.out.println("u.getHost = " + host);
It prints -
u.getHost = null
>From http://download.oracle.com/javase/1.4.2/docs/api/java/net/URI.html , I found out that '=' sign is a valid character.
Correct me if I am wrong. Is there a way out of this. I can't change my hostname. I hard-coded the address and built the jar for now. :)
Thanks,
Suraj
> java.lang.NullPointerException in reduce task
> ---------------------------------------------
>
> Key: MAPREDUCE-2097
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2097
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: task
> Affects Versions: 0.20.2
> Environment: RHEL 5.5
> Reporter: vaibhav negi
>
> While executing hive query "select count(*) from table " , i got this error message
> Ended Job = job_201009291356_0003 with errors
> FAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.MapRedTask
> On investigating task tracker logs , i found out
> 2010-09-29 14:31:46,839 WARN org.apache.hadoop.conf.Configuration: /home/hadoop/mapred/local/taskTracker/jobcache/job_201009291356_0003/attempt_201009291356_0003_r_000000_3/job.xml:a attempt to override final parameter: mapred.local.dir; Ignoring.
> 2010-09-29 14:31:46,862 WARN org.apache.hadoop.conf.Configuration: /home/hadoop/mapred/local/taskTracker/jobcache/job_201009291356_0003/attempt_201009291356_0003_r_000000_3/job.xml:a attempt to override final parameter: mapred.job.tracker; Ignoring.
> 2010-09-29 14:31:46,943 INFO org.apache.hadoop.metrics.jvm.JvmMetrics: Initializing JVM Metrics with processName=SHUFFLE, sessionId=
> 2010-09-29 14:31:47,133 WARN org.apache.hadoop.conf.Configuration: /home/hadoop/mapred/local/taskTracker/jobcache/job_201009291356_0003/attempt_201009291356_0003_r_000000_3/job.xml:a attempt to override final parameter: mapred.local.dir; Ignoring.
> 2010-09-29 14:31:47,133 WARN org.apache.hadoop.conf.Configuration: /home/hadoop/mapred/local/taskTracker/jobcache/job_201009291356_0003/attempt_201009291356_0003_r_000000_3/job.xml:a attempt to override final parameter: dfs.data.dir; Ignoring.
> 2010-09-29 14:31:47,143 WARN org.apache.hadoop.conf.Configuration: /home/hadoop/mapred/local/taskTracker/jobcache/job_201009291356_0003/attempt_201009291356_0003_r_000000_3/job.xml:a attempt to override final parameter: mapred.job.tracker; Ignoring.
> 2010-09-29 14:31:47,143 WARN org.apache.hadoop.conf.Configuration: /home/hadoop/mapred/local/taskTracker/jobcache/job_201009291356_0003/attempt_201009291356_0003_r_000000_3/job.xml:a attempt to override final parameter: dfs.name.dir; Ignoring.
> 2010-09-29 14:31:47,209 INFO org.apache.hadoop.mapred.ReduceTask: ShuffleRamManager: MemoryLimit=141387360, MaxSingleShuffleLimit=35346840
> 2010-09-29 14:31:47,219 INFO org.apache.hadoop.mapred.ReduceTask: attempt_201009291356_0003_r_000000_3 Thread started: Thread for merging on-disk files
> 2010-09-29 14:31:47,220 INFO org.apache.hadoop.mapred.ReduceTask: attempt_201009291356_0003_r_000000_3 Thread waiting: Thread for merging on-disk files
> 2010-09-29 14:31:47,222 INFO org.apache.hadoop.mapred.ReduceTask: attempt_201009291356_0003_r_000000_3 Thread started: Thread for merging in memory files
> 2010-09-29 14:31:47,223 INFO org.apache.hadoop.mapred.ReduceTask: attempt_201009291356_0003_r_000000_3 Need another 17 map output(s) where 0 is already in progress
> 2010-09-29 14:31:47,224 INFO org.apache.hadoop.mapred.ReduceTask: attempt_201009291356_0003_r_000000_3 Scheduled 0 outputs (0 slow hosts and0 dup hosts)
> 2010-09-29 14:31:47,224 INFO org.apache.hadoop.mapred.ReduceTask: attempt_201009291356_0003_r_000000_3 Thread started: Thread for polling Map Completion Events
> 2010-09-29 14:31:47,233 FATAL org.apache.hadoop.mapred.TaskRunner: attempt_201009291356_0003_r_000000_3 GetMapEventsThread Ignoring exception : java.lang.NullPointerException
> at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:768)
> at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.getMapCompletionEvents(ReduceTask.java:2683)
> at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$GetMapEventsThread.run(ReduceTask.java:2605)
> ReduceTask.java:2683 is : List<MapOutputLocation> loc = mapLocations.get(host)
> where host is:-URI u = URI.create(event.getTaskTrackerHttp()); host = u.getHost() ;
> What's the fix??
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