hadoop 2.2.0 wordcount prg 无法从远程运行

Question

我无法使用 eclipse 从远程计算机运行 hadoop 2.2.0 中的 wordcount 示例。我构建了可运行的 jar 并使用 >java -jar wordcount.jar 执行。我的驱动类代码如下

Configuration conf = new Configuration();      
Job job = new Job(conf, "wordcount");        
conf.set("fs.defaultFS", "hdfs://192.168.117.128:8020/");
conf.set("hadoop.job.ugi", "root");
conf.set("mapred.job.tracker", "192.168.117.128:8021"); 
Path inputPath = new Path("/input/FB_Bank_Comments_abi_required_original.txt");
Path outputPath = new Path("/output/wordcount"+System.currentTimeMillis());     
job.setJobName("wordcount_analysis");
job.setJarByClass(Map.class);       
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);        
job.setMapperClass(Map.class);
job.setReducerClass(Reduce.class);        
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);        
FileInputFormat.addInputPath(job, inputPath);
FileOutputFormat.setOutputPath(job, outputPath);        
job.waitForCompletion(true);

我收到以下错误

Exception in thread "main" java.lang.NullPointerException
    at java.lang.ProcessBuilder.start(Unknown Source)
    at org.apache.hadoop.util.Shell.runCommand(Shell.java:404)
    at org.apache.hadoop.util.Shell.run(Shell.java:379)
    at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:589)
    at org.apache.hadoop.util.Shell.execCommand(Shell.java:678)
    at org.apache.hadoop.util.Shell.execCommand(Shell.java:661)
    at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:639)
    at org.apache.hadoop.fs.RawLocalFileSystem.mkdirs(RawLocalFileSystem.java:435)
    at org.apache.hadoop.fs.FilterFileSystem.mkdirs(FilterFileSystem.java:277)
    at org.apache.hadoop.mapreduce.JobSubmissionFiles.getStagingDir(JobSubmissionFiles.java:125)
    at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:344)
    at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1268)
    at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1265)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Unknown Source)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1491)
    at org.apache.hadoop.mapreduce.Job.submit(Job.java:1265)
    at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:1286)
    at org.myorg.WordCount.main(WordCount.java:69)

我错过了什么？任何帮助将不胜感激

Answer 1

我遇到了同样的错误。最终我找到了原因。输出目录已经存在。我把输出目录删了再运行后就成功了。