问题
I have hadoop cluster version 2.2.0 running with mahout 0.8, is it compatible? Because whenever I run this command:
bin/mahout recommenditembased --input mydata.dat --usersFile user.dat --numRecommendations 2 --output output/ --similarityClassname SIMILARITY_PEARSON_CORRELATION
Give me this error:
Exception in thread "main" java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.JobContext, but class was expected
at org.apache.mahout.common.HadoopUtil.getCustomJobName(HadoopUtil.java:174)
at org.apache.mahout.common.AbstractJob.prepareJob(AbstractJob.java:614)
at org.apache.mahout.cf.taste.hadoop.preparation.PreparePreferenceMatrixJob.run(PreparePreferenceMatrixJob.java:75)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at org.apache.mahout.cf.taste.hadoop.item.RecommenderJob.run(RecommenderJob.java:158)
at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)
at org.apache.mahout.cf.taste.hadoop.item.RecommenderJob.main(RecommenderJob.java:312)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:622)
at org.apache.hadoop.util.ProgramDriver$ProgramDescription.invoke(ProgramDriver.java:72)
at org.apache.hadoop.util.ProgramDriver.run(ProgramDriver.java:144)
at org.apache.hadoop.util.ProgramDriver.driver(ProgramDriver.java:152)
at org.apache.mahout.driver.MahoutDriver.main(MahoutDriver.java:194)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:622)
at org.apache.hadoop.util.RunJar.main(RunJar.java:212)
Or Im wrong? Any info would be helpful.
回答1:
No, it does not work with Hadoop 2.x, someone else got the same error message like you.
It seems that at the very least it would require a recompile.
And more people are having the same problems: how can I compile/using mahout for hadoop 2.0?
回答2:
About an hour ago Mahout has officially added support to Hadoop 2.x in the master branch (see MAHOUT-1329)
Checkout the code here https://github.com/apache/mahout and recompile using:
mvn clean package -Dhadoop2.version=2.2.0
Try and see if that works.
回答3:
You can get the source code from github https://github.com/apache/mahout and run the following command
mvn -Dhadoop2.version=2.2.0 -DskipTests clean install
Then, you can find the release package in distribution/target/
来源：https://stackoverflow.com/questions/20911821/hadoop-2-2-0-is-compatible-with-mahout-0-8