Reducer sort failed due to wrong key class
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Key: HADOOP-2164
URL: https://issues.apache.org/jira/browse/HADOOP-2164
Project: Hadoop
Issue Type: Bug
Components: mapred
Reporter: Runping Qi
One of my job's reducers failed due to the following exception:
java.io.IOException: wrong key class: class org.apache.hadoop.io.LongWritable
is not class org.apache.hadoop.io.Text
at
org.apache.hadoop.io.SequenceFile$Sorter$SegmentDescriptor.nextRawKey(SequenceFile.java:2733)
at
org.apache.hadoop.io.SequenceFile$Sorter$MergeQueue.merge(SequenceFile.java:2542)
at
org.apache.hadoop.io.SequenceFile$Sorter.merge(SequenceFile.java:2326)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:291)
at
org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:1760)
I checked the segment files to be merged on the node running the reducer,
and founded that one of the map output file did record
org.apache.hadoop.io.LongWritable as its key class!
The question is how that happened? My job conf specified Text as the map output
key class, and other map output files had
the correct key class!
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