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Date: Fri, 21 Dec 2007 22:40:43 -0800 (PST)
From: "Koji Noguchi (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Created: (HADOOP-2486) Dropping records at reducer.
  InMemoryFileSystem NPE.
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Dropping records at reducer.  InMemoryFileSystem NPE.
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                 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


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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