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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