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https://issues.apache.org/jira/browse/HADOOP-2486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12554090
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Koji Noguchi commented on HADOOP-2486:
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Here are the counters from the two run.
First ====
Counter Map Reduce Total
Job Counters Launched map tasks 0 0 512
Launched reduce tasks 0 0 60
Data-local map tasks 0 0 41
Map-Reduce Framework Map input records 311,740,575 0
311,740,575
Map output records *311,740,575* 0 311,740,575
Map input bytes 41,488,968,916 0 41,488,968,916
Map output bytes 129,088,071,619 0 129,088,071,619
Reduce input groups 0 53,332,945 53,332,945
Reduce input records 0 *311,680,380* 311,680,380
Reduce output records 0 311,680,380 311,680,380
Second.====
Counter Map Reduce Total
Job Counters Launched map tasks 0 0 512
Launched reduce tasks 0 0 60
Data-local map tasks 0 0 42
Map-Reduce Framework Map input records 311,740,575 0
311,740,575
Map output records *311,740,575* 0 311,740,575
Map input bytes 41,488,968,916 0 41,488,968,916
Map output bytes 129,088,071,619 0 129,088,071,619
Reduce input groups 0 53,343,415 53,343,415
Reduce input records 0 *311,740,575* 311,740,575
Reduce output records 0 311,740,575 311,740,575
> 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
>
> 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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