hadoop向mysql写入数据,map执行100%,reduce不执行

Question

开发环境: haddoop2.7.1,jdk1.7
功能描述:从文件中读取数据写入mysql.
问题:为什么程序执行map100%,combine100%,reduce0%.程序没有运行到reduce中

package b508.demo;

import java.io.IOException;

import java.io.DataInput;

import java.io.DataOutput;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.io.Writable;

import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;

import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
import org.apache.hadoop.mapreduce.lib.db.DBOutputFormat;
import org.apache.hadoop.mapreduce.lib.db.DBWritable;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

public class WriteDB3 {

// Map处理过程

public static class Map extends Mapper<Object, Text, Text, IntWritable> {

    private final static IntWritable one = new IntWritable(1);

    private Text word = new Text();

    @Override
    protected void map(Object key, Text value, Mapper<Object, Text, Text, IntWritable>.Context context)
            throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        String line = value.toString();

        StringTokenizer tokenizer = new StringTokenizer(line);

        while (tokenizer.hasMoreTokens()) {

            word.set(tokenizer.nextToken());
            context.write(word, one);
        }
        System.out.println("MAP");

    }
}
// combine

public static class Combine extends Reducer<Text, IntWritable, Text, IntWritable> {

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values,
            Reducer<Text, IntWritable, Text, IntWritable>.Context context)
                    throws IOException, InterruptedException {

        int sum = 0;
        for (IntWritable num : values) {
            sum += num.get();
        }
        context.write(key, new IntWritable(sum));
    //  System.out.println(key);
    //  System.out.println(sum);
    //  System.out.println("Combine over");

    }
}
// Reduce处理过程

public static class Reduce extends Reducer<Text, IntWritable, WordRecord, Text> {

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values,
            Reducer<Text, IntWritable, WordRecord, Text>.Context context) throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        System.out.println("reduce begin");
        int sum = 0;
        for (IntWritable num : values) {
            sum += num.get();
        }
        WordRecord wordcount = new WordRecord();

        wordcount.word = key.toString();

        wordcount.number = sum;
        context.write(wordcount, new Text());
        System.out.println("reduce over");
    }

}

public static class WordRecord implements Writable, DBWritable {

    public String word;

    public int number;

    @Override

    public void readFields(DataInput in) throws IOException {

        this.word = Text.readString(in);

        this.number = in.readInt();

    }

    @Override

    public void write(DataOutput out) throws IOException {

        Text.writeString(out, this.word);

        out.writeInt(this.number);

    }

    @Override

    public void readFields(ResultSet result) throws SQLException {

        this.word = result.getString(1);

        this.number = result.getInt(2);

    }

    @Override

    public void write(PreparedStatement stmt) throws SQLException {

        stmt.setString(1, this.word);

        stmt.setInt(2, this.number);

    }

}

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

    Configuration conf = new Configuration();

    Job job = Job.getInstance(conf, "word");

    job.setJarByClass(WriteDB2.class);
    job.setMapperClass(Map.class);

    job.setCombinerClass(Combine.class);
    job.setReducerClass(Reduce.class);

    job.setMapOutputKeyClass(Text.class);
    job.setMapOutputValueClass(IntWritable.class);

    job.setOutputKeyClass(WordRecord.class);
    job.setOutputValueClass(Text.class);
    Path path = new Path("hdfs://master:9000/input");
    FileInputFormat.addInputPath(job, path);


    // 建立数据库连接

    DBConfiguration.configureDB(conf, "com.mysql.jdbc.Driver",

    "jdbc:mysql://localhost:3306/school", "root", "123456");

    // 写入"wordcount"表中的数据

    String[] fields = { "word", "number" };

    DBOutputFormat.setOutput(job, "wordcount", fields);


    job.waitForCompletion(true); 



}

}

Answer 1

http://my.oschina.net/leejun2005/blog/147941