[jira] [Reopened] (HADOOP-13410) RunJar adds the content of the jar twice to the classpath

["Sangjin Lee (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-13410?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sangjin Lee reopened HADOOP-13410:
----------------------------------

The commit has been reverted.

It turns out that MR {{JobConf.setJarByClass()}} (by using {{ClassUtil.findContainingJar()}} ) looks for the jar that contains the class. If the class is not found in a jar, the job jar is not set.

[~yuanbo], I think we may want to remove the "/" entry rather than the jar. It would be great if we can add a small unit test to confirm the issue and the fix.

> RunJar adds the content of the jar twice to the classpath
> ---------------------------------------------------------
>
>                 Key: HADOOP-13410
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13410
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>            Reporter: Sangjin Lee
>            Assignee: Yuanbo Liu
>             Fix For: 3.0.0-alpha2
>
>         Attachments: HADOOP-13410.001.patch
>
>
> Today when you run a "hadoop jar" command, the jar is unzipped to a temporary location and gets added to the classloader.
> However, the original jar itself is still added to the classpath.
> {code}
>       List<URL> classPath = new ArrayList<>();
>       classPath.add(new File(workDir + "/").toURI().toURL());
>       classPath.add(file.toURI().toURL());
>       classPath.add(new File(workDir, "classes/").toURI().toURL());
>       File[] libs = new File(workDir, "lib").listFiles();
>       if (libs != null) {
>         for (File lib : libs) {
>           classPath.add(lib.toURI().toURL());
>         }
>       }
> {code}
> As a result, the contents of the jar are present in the classpath *twice* and are completely redundant. Although this does not necessarily cause correctness issues, some stricter code written to require a single presence of files may fail.
> I cannot think of a good reason why the jar should be added to the classpath if the unjarred content was added to it. I think we should remove the jar from the classpath.



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