MapReduce不产生输出 [英] MapReduce doesn't produce an output
问题描述
我想在文本文件上执行一个简单的MapReduce,但是它没有输出.这是我的代码:
I want to execute a simple MapReduce on textfile but it doesn't an output. This is my code:
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
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.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 WordCount {
public static class TokenizerMapper
extends Mapper<Object, Text, Text, IntWritable>{
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(Object key, Text value, Context context
) throws IOException, InterruptedException {
StringTokenizer itr = new StringTokenizer(value.toString());
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
context.write(word, one);
}
}
}
public static class IntSumReducer
extends Reducer<Text,IntWritable,Text,IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values,
Context context
) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum) ;
context.write(key, result);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "word count");
job.setJarByClass(WordCount.class);
job.setMapperClass(TokenizerMapper.class);
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
在执行jar文件的过程中,我收到以下错误消息:
I receive this errors during jar file execution:
17/05/07 23:10:53 WARN mapred.LocalJobRunner: job_local973452829_0001
java.lang.Exception: org.apache.hadoop.mapreduce.task.reduce.Shuffle$ShuffleError: error in shuffle in localfetcher#1
at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:529)
Caused by: org.apache.hadoop.mapreduce.task.reduce.Shuffle$ShuffleError: error in shuffle in localfetcher#1
at org.apache.hadoop.mapreduce.task.reduce.Shuffle.run(Shuffle.java:134)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:376)
at org.apache.hadoop.mapred.LocalJobRunner$Job$ReduceTaskRunnable.run(LocalJobRunner.java:319)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.FileNotFoundException: /app/hadoop/tmp%20/mapred/local/localRunner/hduser/jobcache/job_local973452829_0001/attempt_local973452829_0001_m_000000_0/output/file.out.index
at org.apache.hadoop.fs.RawLocalFileSystem.open(RawLocalFileSystem.java:193)
at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:764)
at org.apache.hadoop.io.SecureIOUtils.openFSDataInputStream(SecureIOUtils.java:156)
at org.apache.hadoop.mapred.SpillRecord.<init>(SpillRecord.java:70)
at org.apache.hadoop.mapred.SpillRecord.<init>(SpillRecord.java:62)
at org.apache.hadoop.mapred.SpillRecord.<init>(SpillRecord.java:57)
at org.apache.hadoop.mapreduce.task.reduce.LocalFetcher.copyMapOutput(LocalFetcher.java:123)
at org.apache.hadoop.mapreduce.task.reduce.LocalFetcher.doCopy(LocalFetcher.java:101)
at org.apache.hadoop.mapreduce.task.reduce.LocalFetcher.run(LocalFetcher
我的代码有什么问题?我在Hadoop 2.4和Hadoop 2.4下使用
What's the problem in my code? I'm under ubuntu 14.04 with hadoop 2.4
推荐答案
这是您的错误的一部分:
This is a part of your error:
原因:java.io.FileNotFoundException:/app/hadoop/tmp%20/mapred/local/localRunner/hduser/jobcache/job_local973452829_0001/attempt_local973452829_0001_m_000000_0/output/file.out.index
我猜测您的 core-site.xml
中的配置属性 hadoop.tmp.dir
有问题,因为Hadoop无法存储临时输出文件(从Mapper)到磁盘.
I'm guessing it's a problem with the configuration property hadoop.tmp.dir
in your core-site.xml
because Hadoop is unable to store the temporary output files (from Mapper) to your disk.
您可以删除该属性,以便hadoop创建它自己的临时目录来存储中间输出,或将其设置为具有适当权限的某个目录.
You can remove that property so that hadoop creates it's own temporary directory to store the intermediate output or set it to some directory with appropriate permissions.
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