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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