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MapReduce示例-气象站

MaxTemperature.java

package cn.kissoft.hadoop.week05;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class MaxTemperature {

    public static void main(String[] args) throws Exception {
        if (args.length != 2) {
            System.err.println("Usage: MaxTemperature <input path> <output path>");
            System.exit(-1);
        }
        Job job = new Job();
        job.setJarByClass(MaxTemperature.class);
        job.setJobName("Max temperature");
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        job.setMapperClass(MaxTemperatureMapper.class);
        job.setReducerClass(MaxTemperatureReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}



MaxTemperatureMapper.java

package cn.kissoft.hadoop.week05;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class MaxTemperatureMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
    private static final int MISSING = 9999;

    @Override
    public void map(LongWritable key, Text value, Context context)
            throws IOException, InterruptedException {
        String line = value.toString();
        String year = line.substring(0, 4);
        int airTemperature = Integer.parseInt(line.substring(13, 19).trim());
        if (airTemperature != MISSING) {
            context.write(new Text(year), new IntWritable(airTemperature));
        }
    }

}



MaxTemperatureReducer.java

package cn.kissoft.hadoop.week05;

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

public class MaxTemperatureReducer extends Reducer<Text, IntWritable, Text, IntWritable> {

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

        int maxValue = http://www.mamicode.com/Integer.MIN_VALUE;> 



运行结果

[wukong@bd11 guide]$ hadoop jar pc.jar cn.kissoft.hadoop.week05.MaxTemperature ./ch02/1959.txt ./ch02/out/
Warning: $HADOOP_HOME is deprecated.

14/08/15 11:27:15 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
14/08/15 11:27:15 INFO input.FileInputFormat: Total input paths to process : 1
14/08/15 11:27:15 INFO util.NativeCodeLoader: Loaded the native-hadoop library
14/08/15 11:27:15 WARN snappy.LoadSnappy: Snappy native library not loaded
14/08/15 11:27:17 INFO mapred.JobClient: Running job: job_201408150916_0003
14/08/15 11:27:18 INFO mapred.JobClient:  map 0% reduce 0%
14/08/15 11:27:31 INFO mapred.JobClient:  map 100% reduce 0%
14/08/15 11:27:43 INFO mapred.JobClient:  map 100% reduce 100%
14/08/15 11:27:46 INFO mapred.JobClient: Job complete: job_201408150916_0003
14/08/15 11:27:46 INFO mapred.JobClient: Counters: 29
14/08/15 11:27:46 INFO mapred.JobClient:   Job Counters 
14/08/15 11:27:46 INFO mapred.JobClient:     Launched reduce tasks=1
14/08/15 11:27:46 INFO mapred.JobClient:     SLOTS_MILLIS_MAPS=14494
14/08/15 11:27:46 INFO mapred.JobClient:     Total time spent by all reduces waiting after reserving slots (ms)=0
14/08/15 11:27:46 INFO mapred.JobClient:     Total time spent by all maps waiting after reserving slots (ms)=0
14/08/15 11:27:46 INFO mapred.JobClient:     Launched map tasks=1
14/08/15 11:27:46 INFO mapred.JobClient:     Data-local map tasks=1
14/08/15 11:27:46 INFO mapred.JobClient:     SLOTS_MILLIS_REDUCES=12558
14/08/15 11:27:46 INFO mapred.JobClient:   File Output Format Counters 
14/08/15 11:27:46 INFO mapred.JobClient:     Bytes Written=9
14/08/15 11:27:46 INFO mapred.JobClient:   FileSystemCounters
14/08/15 11:27:46 INFO mapred.JobClient:     FILE_BYTES_READ=9773826
14/08/15 11:27:46 INFO mapred.JobClient:     HDFS_BYTES_READ=27544475
14/08/15 11:27:46 INFO mapred.JobClient:     FILE_BYTES_WRITTEN=14776914
14/08/15 11:27:46 INFO mapred.JobClient:     HDFS_BYTES_WRITTEN=9
14/08/15 11:27:46 INFO mapred.JobClient:   File Input Format Counters 
14/08/15 11:27:46 INFO mapred.JobClient:     Bytes Read=27544368
14/08/15 11:27:46 INFO mapred.JobClient:   Map-Reduce Framework
14/08/15 11:27:46 INFO mapred.JobClient:     Map output materialized bytes=4886910
14/08/15 11:27:46 INFO mapred.JobClient:     Map input records=444264
14/08/15 11:27:46 INFO mapred.JobClient:     Reduce shuffle bytes=4886910
14/08/15 11:27:46 INFO mapred.JobClient:     Spilled Records=1332792
14/08/15 11:27:46 INFO mapred.JobClient:     Map output bytes=3998376
14/08/15 11:27:46 INFO mapred.JobClient:     Total committed heap usage (bytes)=219496448
14/08/15 11:27:46 INFO mapred.JobClient:     CPU time spent (ms)=6770
14/08/15 11:27:46 INFO mapred.JobClient:     Combine input records=0
14/08/15 11:27:46 INFO mapred.JobClient:     SPLIT_RAW_BYTES=107
14/08/15 11:27:46 INFO mapred.JobClient:     Reduce input records=444264
14/08/15 11:27:46 INFO mapred.JobClient:     Reduce input groups=1
14/08/15 11:27:46 INFO mapred.JobClient:     Combine output records=0
14/08/15 11:27:46 INFO mapred.JobClient:     Physical memory (bytes) snapshot=310345728
14/08/15 11:27:46 INFO mapred.JobClient:     Reduce output records=1
14/08/15 11:27:46 INFO mapred.JobClient:     Virtual memory (bytes) snapshot=1455665152
14/08/15 11:27:46 INFO mapred.JobClient:     Map output records=444264
[wukong@bd11 guide]$ hadoop fs -ls ./ch02/out/ 
Warning: $HADOOP_HOME is deprecated.

Found 3 items
-rw-r--r--   1 wukong supergroup          0 2014-08-15 11:27 /user/wukong/ch02/out/_SUCCESS
drwxr-xr-x   - wukong supergroup          0 2014-08-15 11:27 /user/wukong/ch02/out/_logs
-rw-r--r--   1 wukong supergroup          9 2014-08-15 11:27 /user/wukong/ch02/out/part-r-00000
[wukong@bd11 guide]$ hadoop fs -cat ./ch02/out/part-r-00000
Warning: $HADOOP_HOME is deprecated.

1959    418



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