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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);
}
}