这里有一个简单的Map缩小作业。最初,这只是将输入目录中的文件复制到输出目录的一种简单方法。map阶段完成,但是reduce阶段挂起。我做错什么了?这是一个小的代码量,这里是整个工作:
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
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;
public class MapDemo {
public static class Map extends Mapper<Object, Text, Text, NullWritable> {
private Text word = new Text();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
String line = value.toString();
word.set(line);
context.write(word, NullWritable.get());
}
}
public static class Reduce extends Reducer<Text, NullWritable, Text, NullWritable> {
public void reduce(Text key, Iterable<NullWritable> values, Context context) throws IOException, InterruptedException {
context.write(key, NullWritable.get());
}
}
public static void main(String[] args) throws Exception {
Configuration configuration = new Configuration();
Job job = new Job(configuration, "MapDemo");
job.setJarByClass(WordCount.class);
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);
job.setNumReduceTasks(10);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(NullWritable.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
它执行到这里然后挂起:
$ hadoop jar target/map-demo.jar /Users/dwilliams/input /Users/dwilliams/output
2013-09-16 11:51:19.131 java[6041:1703] Unable to load realm info from SCDynamicStore
13/09/16 11:51:19 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
13/09/16 11:51:19 INFO input.FileInputFormat: Total input paths to process : 1
13/09/16 11:51:19 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
13/09/16 11:51:19 WARN snappy.LoadSnappy: Snappy native library not loaded
13/09/16 11:51:19 INFO mapred.JobClient: Running job: job_201309150844_0012
13/09/16 11:51:20 INFO mapred.JobClient: map 0% reduce 0%
13/09/16 11:51:25 INFO mapred.JobClient: map 100% reduce 0%
... then nothing
这里怎么了?我该怎么解决这个问题?
2条答案
按热度按时间92dk7w1h1#
我的问题是记忆力。我使用的是virtualbox,我使用的是默认的512m内存。内存增加到2g后,一切正常。
5vf7fwbs2#
需要重新格式化namenode并重新启动守护进程。这是在我的mac osx上,可能和睡觉有关。