How do I build/run this simple Mahout program without getting exceptions?
I would like to run this code which I found in Mahout In Action:
package org.help;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.mahout.math.DenseVector;
import org.apache.mahout.math.NamedVector;
import org.apache.mahout.math.VectorWritable;
public class SeqPrep {
public static void main(String args[]) throws IOException{
List<NamedVector> apples = new ArrayList<NamedVector>();
NamedVector apple;
apple = new NamedVector(new DenseVector(new double[]{0.11, 510, 1}), "small round green apple");
apples.add(apple);
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Path path = new Path("appledata/apples");
SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf, path, Text.class, VectorWritable.class);
VectorWritable vec = new VectorWritable();
for(NamedVector vector : apples){
vec.set(vector);
writer.append(new Text(vector.getName()), vec);
}
writer.close();
SequenceFile.Reader reader = new SequenceFile.Reader(fs, new Path("appledata/apples"), conf);
Text key = new Text();
VectorWritable value = new VectorWritable();
while(reader.next(key, value)){
System.out.println(key.toString() + " , " + value.get().asFormatString());
}
reader.close();
}
}
I compile it with:
$ javac -classpath :/usr/local/hadoop-1.0.3/hadoop-core-1.0.3.jar:/home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT.jar:/home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar:/home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-sources.jar -d myjavac/ SeqPrep.java
I jar it:
$ jar -cvf SeqPrep.jar -C myjavac/ .
Now I'd like to run it on my local hadoop node. I've tried:
hadoop jar SeqPrep.jar org.help.SeqPrep
But I get:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/mahout/math/Vector
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)
So I tried using the libjars parameter:
$ hadoop jar SeqPrep.jar org.help.SeqPrep -libjars /home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT.jar -libjars /home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar -libjars /home/hduser/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-sources.jar -libjars /home/hduser/mahout/trunk/math/target/mahout-math-0.8-SNAPSHOT.jar -libjars /home/hduser/mahout/trunk/math/target/mahout-math-0.8-SNAPSHOT-sources.jar
and got the same problem. I don't know what else to try.
My eventual goal is to be able to read a .csv file on the hadoop fs into a sparse matrix and then multiply it by a random vector.
edit: Looks like Razvan got it (note: see below for another way to do this that does not mess with your hadoop installation). For reference:
$ find /usr/local/hadoop-1.0.3/. |grep mah
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT-tests.jar
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT.jar
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT-job.jar
/usr/local/hadoop-1.0.3/./lib/mahout-core-0.8-SNAPSHOT-sources.jar
/usr/local/hadoop-1.0.3/./lib/mahout-math-0.8-SNAPSHOT-sources.jar
/usr/local/hadoop-1.0.3/./lib/mahout-math-0.8-SNAPSHOT-tests.jar
/usr/local/hadoop-1.0.3/./lib/mahout-math-0.8-SNAPSHOT.jar
and then:
$hadoop jar SeqPrep.jar org.help.SeqPrep
small round green apple , small round green apple:{0:0.11,1:510.0,2:1.0}
edit: I'm trying to do this without copying the mahout jars into the hadoop lib/
$ rm /usr/local/hadoop-1.0.3/lib/mahout-*
and then of course:
hadoop jar SeqPrep.jar org.help.SeqPrep
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/mahout/math/Vector
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)
Caused by: java.lang.ClassNotFoundException: org.apache.mahout.math.Vector
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
and when I try the mahout job file:
$hadoop jar ~/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar org.help.SeqPrep
Exception in thread "main" java.lang.ClassNotFoundException: org.help.SeqPrep
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.apache.hadoop.util.RunJar.main(RunJar.java:149)
If I try to include the .jar file I made:
$ hadoop jar ~/mahout/trunk/core/target/mahout-core-0.8-SNAPSHOT-job.jar SeqPrep.jar org.help.SeqPrep
Exception in thread "main" java.lang.ClassNotFoundException: SeqPrep.jar
edit: Apparently I can only send one jar at a time to hadoop. This means I need to add the class I made into the mahout core job file:
~/mahout/trunk/core/target$ cp mahout-core-0.8-SNAPSHOT-job.jar mahout-core-0.8-SNAPSHOT-job.jar_backup
~/mahout/trunk/core/target$ cp ~/workspace/seqprep/bin/org/help/SeqPrep.class .
~/mahout/trunk/core/target$ jar uf mahout-core-0.8-SNAPSHOT-job.jar SeqPrep.class
And then:
~/mahout/trunk/core/target$ hadoop jar mahout-core-0.8-SNAPSHOT-job.jar org.help.SeqPrep
Exception in thread "main" java.lang.ClassNotFoundException: org.help.SeqPrep
edit: Ok, now I can do it without messing with my hadoop installation. I was updating the .jar wrong in that previous edit. It should be:
~/mahout/trunk/core/target$ jar uf mahout-core-0.8-SNAPSHOT-job.jar org/help/SeqPrep.class
then:
~/mahout/trunk/core/target$ hadoop jar mahout-core-0.8-SNAPSHOT-job.jar org.help.SeqPrep
small round green apple , small round green apple:{0:0.11,1:510.0,2:1.0}
Answer
You need to use the "job" JAR file provided by Mahout. It packages up all the dependencies. You need to add your classes to it too. This is how all the Mahout examples work. You shouldn't put Mahout jars in the Hadoop lib since that sort of "installs" a program too deeply in Hadoop.