Question

我不明白如何使作业使用相同的输出目录目录中写入不同的文件。我曾尝试过表彰和ucommenting这一行，但它仍然无法正常工作。我得到以下内容我发表评论的例外情况。无论如何在代码中我试图运行两个使用相同的reducer但使用不同的mapper分隔作业。

编辑：不，一个作业的输出不是另一个作业的输入，原因我希望它们在同一个文件夹中是因为它们是另一个地图的输入减少我想做的工作。

FileOutputFormat.setOutputPath(job, new Path(args[1]));

11/04/14 13:33:11 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same.
Exception in thread "main" org.apache.hadoop.mapred.InvalidJobConfException: Output directory not set.
    at org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:120)
    at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:770)
    at org.apache.hadoop.mapreduce.Job.submit(Job.java:432)
    at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:447)
    at org.myorg.WordCount.main(WordCount.java:123)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:156)

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        // String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        // if (otherArgs.length != 2) {
        //   System.err.println("Usage: wordcount <in> <out>");
        //   System.exit(2);
        // }
        Job job = new Job(conf, "Job1");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(Mapper1.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]));

        job.waitForCompletion(true);

        FileSystem hdfs = FileSystem.get(conf);
        Path fromPath = new Path("/user/hadoop/output/part-r-00000");
        Path toPath = new Path("/user/hadoop/output/output1");

        // renaming to output1
        boolean isRenamed = hdfs.rename(fromPath, toPath);
        if (isRenamed)
        {
            System.out.println("Renamed to /user/hadoop/output/output1!");
        }
        else
        {
            System.out.println("Not Renamed!");
        }

        job = new Job(conf, "Job2");
        job.setJarByClass(WordCount.class);
        job.setMapperClass(Mapper2.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);
    }

在我的代码中添加以下内容会导致其他错误：

    job.setInputFormatClass(FileInputFormat.class);
    job.setOutputFormatClass(FileOutputFormat.class);

    FileInputFormat.addInputPath(job, new Path(args[0]));
    FileOutputFormat.setOutputPath(job, new Path(args[1]));

System.exit（job.waitForCompletion（true）？0：1）;

Exception in thread "main" java.lang.RuntimeException: java.lang.InstantiationException
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:115)
    at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:768)
    at org.apache.hadoop.mapreduce.Job.submit(Job.java:432)
    at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:447)
    at org.myorg.WordCount.main(WordCount.java:135)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:156)
Caused by: java.lang.InstantiationException
    at sun.reflect.InstantiationExceptionConstructorAccessorImpl.newInstance(InstantiationExceptionConstructorAccessorImpl.java:30)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    at org.apache.hadoop.util.ReflectionUtils.newInstance(ReflectionUtils.java:113)
    ... 9 more

Answer 1

您必须为第二个作业提供新的Configuration对象。 BTW为什么不使用这些方法输出格式？

job.setInputFormatClass（FileInputFormat.class）; job.setOutputFormatClass（FileOutputFormat.class）;

这是一篇关于递归工作的博文，这与你正在做的事情完全相同 http://codingwiththomas.blogspot.com/2011/04/controlling-hadoop-job-recursion.html

编辑：顺便说一句，你打算写入一个文件夹是什么，它是前一个工作的输出，也就是新工作的输入？这只会导致另一个异常，例如：“输出路径已经存在”。

Answer 2

所有文件不需要位于同一目录中。您的第三个作业可以有多个输入路径（目录或文件）。

见

FileInputFormat.addInputPaths(JobConf conf, String commaSeparatedPaths)

和朋友们......

在hadoop经营另一份工作

System.exit（job.waitForCompletion（true）？0：1）;

2 个答案: