负载均衡

package skew;

import java.io.IOException;
import java.util.Random;

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.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.output.FileOutputFormat;

import cn.edu360.mr.wc.JobSubmitterLinuxToYarn;
import cn.edu360.mr.wc.WordcountMapper;
import cn.edu360.mr.wc.WordcountReducer;

public class SkewWordcount {
	
	public static class SkewWordcountMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
		//mapper类里的东西在整个map过程中,所有的mapper同用
		Random random = new Random();
		Text k = new Text();
		IntWritable v = new IntWritable(1);
		int numReduceTasks = 0;
		@Override//setup在执行maptask前调用一次
		protected void setup(Mapper<LongWritable, Text, Text, IntWritable>.Context context)
				throws IOException, InterruptedException {
			numReduceTasks = context.getNumReduceTasks();
		}
		@Override
		protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

			String[] words = value.toString().split(" ");
			for (String w : words) {
				k.set(w + "\001" + random.nextInt(numReduceTasks));
				context.write(k, v);
			}
		}
	}

	public static class SkewWordcountReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
		IntWritable v = new IntWritable();

		@Override
		protected void reduce(Text key, Iterable<IntWritable> values, Context context)
				throws IOException, InterruptedException {
			int count = 0;
			for (IntWritable value : values) {
				count += value.get();
			}
			v.set(count);
			context.write(key, v);
		}
	}

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

		
		Configuration conf = new Configuration();
		
		Job job = Job.getInstance(conf);
		
		job.setJarByClass(SkewWordcount.class);
		
		job.setMapperClass(SkewWordcountMapper.class);
		job.setReducerClass(SkewWordcountReducer.class);
		
		job.setMapOutputKeyClass(Text.class);
		job.setMapOutputValueClass(IntWritable.class);
		
		// 设置maptask端的局部聚合逻辑类
		job.setCombinerClass(SkewWordcountReducer.class);
		
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(IntWritable.class);
		
		FileInputFormat.setInputPaths(job, new Path("f:/input"));
		FileOutputFormat.setOutputPath(job, new Path("f:/skew-out"));
		
		job.setNumReduceTasks(3);
		
		boolean res = job.waitForCompletion(true);
		System.exit(res?0:1);
	
	}
}