Reducer threw IOEOFException
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Key: HADOOP-156
URL: http://issues.apache.org/jira/browse/HADOOP-156
Project: Hadoop
Type: Bug
Reporter: Runping Qi
A job was running with all the map tasks completed.
The reducers were appending the intermediate files into the large intermediate
file.
java.io.EOFException was thrown when the record reader tried to read the
version number
during initialization. Here is the stack trace:
java.io.EOFException
at java.io.DataInputStream.readFully(DataInputStream.java:178)
at java.io.DataInputStream.readFully(DataInputStream.java:152)
at org.apache.hadoop.io.SequenceFile$Reader.init(SequenceFile.java:251)
at org.apache.hadoop.io.SequenceFile$Reader.(SequenceFile.java:236)
at org.apache.hadoop.io.SequenceFile$Reader.(SequenceFile.java:226)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:205)
at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:709)
Appearantly, the intermediate file was empty. I suspect that one map task
generated empty intermidiate files for all the reducers, since all the reducers
failed at the same place, and failed at the same place during retries.
Unfortunately, we cannot know which map task generated the empty files,
since the exception does not offer any clue.
One simple enhancement is that the record reader should catch IOException and
re-throw it with additional
information, such as the file name.
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