Question

我试图在第7章中运行hello world示例。我在eclipse中创建了以下内容，然后将其打包到jar中： -

package com.mycode.mahout
import java.io.File;
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.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.mahout.clustering.WeightedVectorWritable;
import org.apache.mahout.clustering.kmeans.Cluster;
import org.apache.mahout.clustering.kmeans.KMeansDriver;
import org.apache.mahout.common.distance.EuclideanDistanceMeasure;
import org.apache.mahout.math.RandomAccessSparseVector;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;

public class SimpleKMeansClustering {
  public static final double[][] points = { {1, 1}, {2, 1}, {1, 2},
                                           {2, 2}, {3, 3}, {8, 8},
                                           {9, 8}, {8, 9}, {9, 9}};

  public static void writePointsToFile(List<Vector> points,
                                       String fileName,
                                       FileSystem fs,
                                       Configuration conf) throws IOException {
    Path path = new Path(fileName);
    SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf,
        path, LongWritable.class, VectorWritable.class);
    long recNum = 0;
    VectorWritable vec = new VectorWritable();
    for (Vector point : points) {
      vec.set(point);
      writer.append(new LongWritable(recNum++), vec);
    }
    writer.close();
  }

  public static List<Vector> getPoints(double[][] raw) {
    List<Vector> points = new ArrayList<Vector>();
    for (int i = 0; i < raw.length; i++) {
      double[] fr = raw[i];
      Vector vec = new RandomAccessSparseVector(fr.length);
      vec.assign(fr);
      points.add(vec);
    }
    return points;
  }

  public static void main(String args[]) throws Exception {

    int k = 2;

    List<Vector> vectors = getPoints(points);

    File testData = new File("testdata");
    if (!testData.exists()) {
      testData.mkdir();
    }
    testData = new File("testdata/points");
    if (!testData.exists()) {
      testData.mkdir();
    }

    Configuration conf = new Configuration();
    FileSystem fs = FileSystem.get(conf);
    writePointsToFile(vectors, "testdata/points/file1", fs, conf);

    Path path = new Path("testdata/clusters/part-00000");
    SequenceFile.Writer writer = new SequenceFile.Writer(fs, conf,
        path, Text.class, Cluster.class);

    for (int i = 0; i < k; i++) {
      Vector vec = vectors.get(i);
      Cluster cluster = new Cluster(vec, i, new EuclideanDistanceMeasure());
      writer.append(new Text(cluster.getIdentifier()), cluster);
    }
    writer.close();

    KMeansDriver.run(conf, new Path("testdata/points"), new Path("testdata/clusters"),
      new Path("output"), new EuclideanDistanceMeasure(), 0.001, 10,
      true, false);

    SequenceFile.Reader reader = new SequenceFile.Reader(fs,
        new Path("output/" + Cluster.CLUSTERED_POINTS_DIR
                 + "/part-m-00000"), conf);

    IntWritable key = new IntWritable();
    WeightedVectorWritable value = new WeightedVectorWritable();
    while (reader.next(key, value)) {
      System.out.println(value.toString() + " belongs to cluster "
                         + key.toString());
    }
    reader.close();
  }

}

我把它打包成myjob.jar

现在我该如何在群集上执行此操作？

我试过以下： -

hadoop jar myjob.jar com.mycode.mahout.SimpleKMeansClustering 
java -jar myjob.jar
java -cp myjob.jar

我得到了以下错误： -

 [root@node1 tmp]# hadoop jar mahoutfirst.jar com.mahout.emc.SimpleKMeansClustering 
    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:270)
        at org.apache.hadoop.util.RunJar.main(RunJar.java:201)
    Caused by: java.lang.ClassNotFoundException: org.apache.mahout.math.Vector
        at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 3 more

请告知使用mahout运行代码的正确方法是什么。

Answer 1

即使这已经很晚了但是我遇到了类似的问题并且以下方法对我有用，因为我不想使用maven：

1）转到你的mahout安装目录＆amp;寻找* job.jar作为

ls /usr/lib/mahout/
conf  lib       mahout-core-0.5-cdh3u3-job.jar  mahout-examples-0.5-cdh3u3-job.jar  mahout-taste-webapp-0.5-cdh3u3.war

2）将mahout-examples-0.5-cdh3u3-job.jar复制到代码所在的目录

3）使用＆＃34; job＆＃34; JAR文件由Mahout提供。它打包了所有依赖项。您还需要将类添加到其中。当您使用hadoop和mahout库编译您的类时，您已准备好.class文件。

4）将您的类文件添加到目录中的作业jar mahout-core-0.5-cdh3u3-job.jar：

jar uf mahout-core-0.5-cdh3u3-job.jar SimpleKMeansClustering.class

4）使用你的代码运行hadoop jar：

hadoop jar mahout-core-0.5-cdh3u3-job.jar  SimpleKMeansClustering

5）在map-reduce作业结束时，您可以看到：

1.0: [1.000, 1.000] belongs to cluster 0
1.0: [2.000, 1.000] belongs to cluster 0
1.0: [1.000, 2.000] belongs to cluster 0
1.0: [2.000, 2.000] belongs to cluster 0
1.0: [3.000, 3.000] belongs to cluster 0
1.0: [8.000, 8.000] belongs to cluster 1
1.0: [9.000, 8.000] belongs to cluster 1
1.0: [8.000, 9.000] belongs to cluster 1
1.0: [9.000, 9.000] belongs to cluster 1

Answer 2

看看上面发现的非类定义异常，似乎你可能需要在你的Hadoop作业中包含Mahout相关的jar（mahout-core.jar，我猜）。

要将jar传递给整个集群中的映射器，您可能需要使用DistributedCache或-libjar Hadoop选项。后者的想法是explained here。

如何在动作书中的mahout中运行示例

2 个答案: