Hadoop Bloom filter应用示例

 

Hadoop0.20.2 Bloom filter应用示例

2014-06-04 11:55 451人阅读 评论(0) 收藏 举报

1. 简介

    参见《Hadoop in Action》P102 以及 《Hadoop实战（第2版）》（陆嘉恒）P69

    

           

2. 案例

    网上大部分的说明仅仅是按照《Hadoop in Action》中的示例代码给出，这里是Hadoop0.20.2版本，在该版本中已经实现了BloomFilter。

    案例文件如下：

    customers.txt

    1,Stephanie Leung,555-555-5555
    2,Edward Kim,123-456-7890
    3,Jose Madriz,281-330-8004
    4,David Stork,408-555-0000

    -----------------------------------------------------------------

    orders.txt

    3,A,12.95,02-Jun-2008
    1,B,88.25,20-May-2008
    2,C,32.00,30-Nov-2007
    3,D,25.02,22-Jan-2009
    5,E,34.59,05-Jan-2010
    6,F,28.67,16-Jan-2008
    7,G,49.82,24-Jan-2009

    两个文件通过customer ID关联。

3. 代码

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.bloom.BloomFilter;
import org.apache.hadoop.util.bloom.Key;
import org.apache.hadoop.util.hash.Hash;

public class BloomMRMain {
    public static class BloomMapper extends Mapper<Object, Text, Text, Text> {
        BloomFilter bloomFilter = new BloomFilter(10000, 6, Hash.MURMUR_HASH);

        protected void setup(Context context) throws IOException ,InterruptedException {
            Configuration conf = context.getConfiguration();

            String path = "hdfs://localhost:9000/user/hezhixue/input/customers.txt";
            Path file = new Path(path);

            FileSystem hdfs = FileSystem.get(conf);
            FSDataInputStream dis = hdfs.open(file);
            BufferedReader reader = new BufferedReader(new InputStreamReader(dis));
            String temp;
            while ((temp = reader.readLine()) != null) {
//              System.out.println("bloom filter temp:" + temp);
                String[] tokens = temp.split(",");
                if (tokens.length > 0) {
                    bloomFilter.add(new Key(tokens[0].getBytes()));
                }
            }
        }

        protected void map(Object key, Text value, Context context) throws IOException ,InterruptedException {
            //获得文件输入路径
            String pathName = ((FileSplit) context.getInputSplit()).getPath().toString();
            if (pathName.contains("customers")) {
                String data = value.toString();
                String[] tokens = data.split(",");
                if (tokens.length == 3) {
                    String outKey = tokens[0];
                    String outVal = "0" + ":" + tokens[1] + "," + tokens[2];
                    context.write(new Text(outKey), new Text(outVal));
                }
            } else if (pathName.contains("orders")) {
                String data = value.toString();
                String[] tokens = data.split(",");
                if (tokens.length == 4) {
                    String outKey = tokens[0];
                    System.out.println("in map and outKey:" + outKey);
                    if (bloomFilter.membershipTest(new Key(outKey.getBytes()))) {
                        String outVal = "1" + ":" + tokens[1] + "," + tokens[2]+ "," + tokens[3];
                        context.write(new Text(outKey), new Text(outVal));
                    }
                }
            }
        }
    }

    public static class BloomReducer extends Reducer<Text, Text, Text, Text> {
        ArrayList<Text> leftTable = new ArrayList<Text>();
        ArrayList<Text> rightTable = new ArrayList<Text>();

        protected void reduce(Text key, Iterable<Text> values, Context context) throws IOException ,InterruptedException {

             leftTable.clear();
             rightTable.clear();

            for (Text val : values) {
                String outVal = val.toString();
                System.out.println("key: " + key.toString() + " : " + outVal);
                int index = outVal.indexOf(":");
                String flag = outVal.substring(0, index);
                if ("0".equals(flag)) {
                    leftTable.add(new Text(outVal.substring(index+1)));
                } else if ("1".equals(flag)) {
                    rightTable.add(new Text(outVal.substring(index + 1)));
                }
            }


            if (leftTable.size() > 0 && rightTable.size() > 0) {
                for(Text left : leftTable) {
                    for (Text right : rightTable) {
                        context.write(key, new Text(left.toString() + "," + right.toString()));
                    }
                }
            }
        }
    }

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();

        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();

        if (otherArgs.length != 2) {
          System.err.println("Usage: BloomMRMain <in> <out>");
          System.exit(2);
        }

        Job job = new Job(conf, "BloomMRMain");
        job.setJarByClass(BloomMRMain.class);

        job.setMapperClass(BloomMapper.class);
        job.setReducerClass(BloomReducer.class);

        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);

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

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));

        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}