Hadoop Eclipse plugin 提交作业异常探究

在配置好Hadoop Eclipse plugin 连接成功后，提交作业时会抛出下面异常:

2013-10-31 9:38:04 org.apache.hadoop.security.UserGroupInformation doAs
严重: PriviledgedActionException as:admin cause:java.io.IOException: Failed to set permissions of path: \home\hadoop\tmp\mapred\staging\admin-454528829\.staging to 0700
Exception in thread "main" java.io.IOException: Failed to set permissions of path: \home\hadoop\tmp\mapred\staging\admin-454528829\.staging to 0700
	at org.apache.hadoop.fs.FileUtil.checkReturnValue(FileUtil.java:689)
	at org.apache.hadoop.fs.FileUtil.setPermission(FileUtil.java:662)
	at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:509)
	at org.apache.hadoop.fs.RawLocalFileSystem.mkdirs(RawLocalFileSystem.java:344)
	at org.apache.hadoop.fs.FilterFileSystem.mkdirs(FilterFileSystem.java:189)
	at org.apache.hadoop.mapreduce.JobSubmissionFiles.getStagingDir(JobSubmissionFiles.java:116)
	at org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:918)
	at org.apache.hadoop.mapred.JobClient$2.run(JobClient.java:912)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:396)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1149)
	at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:912)
	at org.apache.hadoop.mapreduce.Job.submit(Job.java:500)
	at org.apache.hadoop.mapreduce.Job.waitForCompletion(Job.java:530)
	at com.chenzehe.hadoop.action.WordCount.main(WordCount.java:86)

 

网上有些人的解决方法是把该异常的代码注释掉，如下:

这个是Windows下文件权限问题，在Linux下可以正常运行，不存在这样的问题。

解决方法是，修改/hadoop-1.0.2/src/core/org/apache/hadoop/fs/FileUtil.java里面的checkReturnValue，注释掉即可（有些粗暴，在Window下，可以不用检查）：
......
private static void checkReturnValue(boolean rv, File p,
FsPermission permission
) throws IOException {
/**
if (!rv) {
throw new IOException("Failed to set permissions of path: " + p +
" to " +
String.format("%04o", permission.toShort()));
}
**/
}
......

 

该解决方法不尽美，通过跟踪Hadoop提交作业的代码可发现导致问题的原因，下面代码为在main方法中提交作业到hadoop中处理:

	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, "my word count");
		job.setJarByClass(WordCount.class);
		job.setMapperClass(MapClass.class);
		// job.setCombinerClass(ReduceClass.class);
		job.setReducerClass(ReduceClass.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(IntWritable.class);
		FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
		FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}

 提交作业的代码为job.waitForCompletion(true)，跟踪进去代码:

    public boolean waitForCompletion(boolean verbose)
        throws IOException, InterruptedException, ClassNotFoundException
    {
        if(state == JobState.DEFINE)
            submit();
        if(verbose)
            jobClient.monitorAndPrintJob(conf, info);
        else
            info.waitForCompletion();
        return isSuccessful();
    }

 submit()提交方法代码为:

    public void submit()
        throws IOException, InterruptedException, ClassNotFoundException
    {
        ensureState(JobState.DEFINE);
        setUseNewAPI();
        connect();
        info = jobClient.submitJobInternal(conf);
        super.setJobID(info.getID());
        state = JobState.RUNNING;
    }

 里面还是调用了jobClient的方法jobClient.submitJobInternal(conf)，在submitJobInternal()方法中使用status = jobSubmitClient.submitJob(jobId, submitJobDir.toString(), jobCopy.getCredentials())方法来提交job，jobSubmitClient有两个实现如下:

通过看JobClient中的init方法发现默认实例化的是LocalJobRunner对象:

    public void init(JobConf conf)
        throws IOException
    {
        String tracker = conf.get("mapred.job.tracker", "local");
        tasklogtimeout = conf.getInt("mapreduce.client.tasklog.timeout", 60000);
        ugi = UserGroupInformation.getCurrentUser();
        if("local".equals(tracker))
        {
            conf.setNumMapTasks(1);
            jobSubmitClient = new LocalJobRunner(conf);
        } else
        {
            rpcJobSubmitClient = createRPCProxy(JobTracker.getAddress(conf), conf);
            jobSubmitClient = createProxy(rpcJobSubmitClient, conf);
        }
    }

 所以job默认是提交到本地的job tracker，所以运行失败，可以在提交job时设置下conf的mapred.job.tracker属性为集群，如下:

	public static void main(String[] args) throws Exception { 
		Configuration conf = new Configuration();
		conf.set("mapred.job.tracker", "master-2:49001");
		......
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}