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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Assigned: (HADOOP-2486) Dropping records at reducer. InMemoryFileSystem NPE.
Date Sun, 23 Dec 2007 11:31:43 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-2486?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Devaraj Das reassigned HADOOP-2486:
-----------------------------------

    Assignee: Devaraj Das

> Dropping records at reducer.  InMemoryFileSystem NPE.
> -----------------------------------------------------
>
>                 Key: HADOOP-2486
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2486
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.14.3
>            Reporter: Koji Noguchi
>            Assignee: Devaraj Das
>         Attachments: 2486.patch
>
>
> Note: I'm really not sure if this is a bug in my code or in mapred. 
> With my mapreduce job without combiner,  I sometimes see   # of total Map output records
!= # of total Reduce input records. What's weird to me is, when I rerun my code with exact
same input, usually I get an expected #map output recs == #reduce output recs.
> Both jobs finish successfully. No failed tasks. No speculative execution. 
> I ran separate linecount mapred jobs on both the input and the output to see if  the
counters are reporting the correct number. 
> When I looked at all the 513 reducer counter, I found single reducer with different counts
for the two runs. 
> Only error stood out in that  reducer userlog is, 
> {noformat} 
> 2007-12-22 00:19:07,640 INFO org.apache.hadoop.mapred.ReduceTask: task_200712220008_0003_r_000024_0
done copying task_200712220008_0003_m_000288_0 output from qqq856.ppp.com.
> 2007-12-22 00:19:07,640 INFO org.apache.hadoop.mapred.ReduceTask: task_200712220008_0003_r_000024_0
Copying task_200712220008_0003_m_000327_0 output from qqq887.ppp.com.
> 2007-12-22 00:19:07,640 ERROR org.apache.hadoop.mapred.ReduceTask: Map output copy failure:
java.lang.NullPointerException
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$FileAttributes.access$300(InMemoryFileSystem.java:366)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem$InMemoryFileStatus.(InMemoryFileSystem.java:380)
> 	at org.apache.hadoop.fs.InMemoryFileSystem$RawInMemoryFileSystem.getFileStatus(InMemoryFileSystem.java:283)
> 	at org.apache.hadoop.fs.FileSystem.isDirectory(FileSystem.java:423)
> 	at org.apache.hadoop.fs.ChecksumFileSystem.rename(ChecksumFileSystem.java:386)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.copyOutput(ReduceTask.java:716)
> 	at org.apache.hadoop.mapred.ReduceTask$ReduceCopier$MapOutputCopier.run(ReduceTask.java:637)
> 2007-12-22 00:19:07,641 INFO org.apache.hadoop.mapred.ReduceTask: task_200712220008_0003_r_000024_0
done copying task_200712220008_0003_m_000228_0 output from qqq801.ppp.com.
> 2007-12-22 00:19:07,641 INFO org.apache.hadoop.mapred.ReduceTask: task_200712220008_0003_r_000024_0
Copying task_200712220008_0003_m_000337_0 output from qqq841.ppp.com.
> {noformat} 
> Could this error be somehow related to my having different # of records? 

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