seqdirectory throws error in MapReduce mode when using Mahout 1.0-SNAPSHOT with Hadoop 2.2.0

Question

I am trying to run the seqdirectory command in Mahout 1.0-SNAPSHOT with Hadoop 2.2.0. On using the command:

seqdirectory -i input -o output

Stack trace:

Error: java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at org.apache.hadoop.mapreduce.lib.input.CombineFileRecordReader.initNextRecordReader(CombineFileRecordReader.java:164)
    at org.apache.hadoop.mapreduce.lib.input.CombineFileRecordReader.<init>(CombineFileRecordReader.java:126)
    at org.apache.mahout.text.MultipleTextFileInputFormat.createRecordReader(MultipleTextFileInputFormat.java:43)
    at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.<init>(MapTask.java:491)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:734)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:339)
    at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:162)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:415)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1491)
    at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:157)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at org.apache.hadoop.mapreduce.lib.input.CombineFileRecordReader.initNextRecordReader(CombineFileRecordReader.java:155)
    ... 10 more
Caused by: java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.TaskAttemptContext, but class was expected
    at org.apache.mahout.text.WholeFileRecordReader.<init>(WholeFileRecordReader.java:59)
    ... 15 more

I thought this was a problem in Mahout 0.9 and was fixed in the trunk. Any clues how to deal with this? I want to run it in MapReduce mode, so, -xm sequential isn't the answer I'm looking for.

Answer 1

Caused by: java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.TaskAttemptContext, but class was expected

Errors like this always mean you're running something against a version of something that's different from the one it was compiled against. Here, you didn't compile Mahout for Hadoop 2. It does not by nature work with Hadoop 2 without some build changes.