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From "zhihai xu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-6238) MR2 can't run local jobs with -libjars command options which is a regression from MR1
Date Sat, 31 Jan 2015 08:51:34 GMT
zhihai xu created MAPREDUCE-6238:
------------------------------------

             Summary: MR2 can't run local jobs with -libjars command options which is a regression
from MR1
                 Key: MAPREDUCE-6238
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6238
             Project: Hadoop Map/Reduce
          Issue Type: Bug
          Components: mrv2
            Reporter: zhihai xu
            Assignee: zhihai xu
            Priority: Critical


MR2 can't run local jobs with -libjars command options which is a regression from MR1. 
When run MR2 job with -jt local and -libjars, the job fails with java.io.FileNotFoundException:
File does not exist: hdfs://XXXXXXXXXXXXXXX.jar.
But the same command is working in MR1.
I find the problem is because when MR2 run local job using  LocalJobRunner
from JobSubmitter, the JobSubmitter#jtFs is local filesystem,
So copyRemoteFiles will return from [the middle of the function|
https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/JobSubmitter.java#L138]
because source and destination file system are same.
{code}
    if (compareFs(remoteFs, jtFs)) {
      return originalPath;
    }
{code}
The following code at [JobSubmitter.java|https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/JobSubmitter.java#L219]
try to add the destination file to DistributedCache which introduce a bug for local job.
{code}
        Path newPath = copyRemoteFiles(libjarsDir, tmp, conf, replication);
        DistributedCache.addFileToClassPath(
            new Path(newPath.toUri().getPath()), conf);
{code}
Because new Path(newPath.toUri().getPath()) will lose the filesystem information from newPath,
the file added to DistributedCache will use the default Uri filesystem hdfs based on the following
code. This causes the 
 FileNotFoundException when we access the file later at 
 [determineTimestampsAndCacheVisibilities|https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/JobSubmitter.java#L270]
{code}
  public static void addFileToClassPath(Path file, Configuration conf)
    throws IOException {
	  addFileToClassPath(file, conf, file.getFileSystem(conf));
  }
  public static void addFileToClassPath
           (Path file, Configuration conf, FileSystem fs)
        throws IOException {
    String classpath = conf.get(MRJobConfig.CLASSPATH_FILES);
    conf.set(MRJobConfig.CLASSPATH_FILES, classpath == null ? file.toString()
             : classpath + "," + file.toString());
    URI uri = fs.makeQualified(file).toUri();
    addCacheFile(uri, conf);
  }
{code}

Compare to the following [MR1 code|https://github.com/apache/hadoop/blob/branch-1/src/mapred/org/apache/hadoop/mapred/JobClient.java#L811]:
{code}
        Path newPath = copyRemoteFiles(fs, libjarsDir, tmp, job, replication);
        DistributedCache.addFileToClassPath(
          new Path(newPath.toUri().getPath()), job, fs);
{code}
You will see why MR1 doesn't have this issue.
because it passes the local filesystem into  DistributedCache#addFileToClassPath instead of
using the default Uri filesystem hdfs.
We should do the same in MR2.




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