[jira] [Commented] (HADOOP-9450) HADOOP_USER_CLASSPATH_FIRST is not honored; CLASSPATH is PREpended instead of APpended

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

    [ https://issues.apache.org/jira/browse/HADOOP-9450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14128753#comment-14128753 ] 

Sangjin Lee commented on HADOOP-9450:
-------------------------------------

This was borne out of an investigation of a hadoop issue at our company. It appears that prior to this the hadoop configuration directory (HADOOP_CONF_DIR) was always the first entry in the classpath, regardless of HADOOP_USER_CLASSPATH_FIRST or HADOOP_CLASSPATH. But after HADOOP-9450, if HADOOP_USER_CLASSPATH_FIRST is set and the user provides his/her version of *-site.xml through HADOOP_CLASSPATH, the user would end up trumping the hadoop configuration. And I believe it is still the case after Allen's changes (HADOOP-9902).

Is this an intended behavior? What I'm not sure of is whether we expect the client to be able to override the site.xml files the hadoop configuration provides. If that is true, then it is working as desired. If not, we'd need to fix this behavior.

Thoughts?


> HADOOP_USER_CLASSPATH_FIRST is not honored; CLASSPATH is PREpended instead of APpended
> --------------------------------------------------------------------------------------
>
>                 Key: HADOOP-9450
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9450
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: scripts
>            Reporter: Mitch Wyle
>            Assignee: Harsh J
>             Fix For: 1-win, 2.1.0-beta, 1.3.0
>
>         Attachments: HADOOP-9450-branch-1-win.patch, HADOOP-9450-branch-1.patch, HADOOP-9450-branch-2.patch, HADOOP-9450.patch, HADOOP-9450.patch
>
>
> On line 133 of the hadoop shell wrapper, CLASSPATH is set as:
> CLASSPATH=${CLASSPATH}:${HADOOP_CLASSPATH}
> Notice that the built-up CLASSPATH, along with all the libs and unwanted JARS are pre-pended BEFORE the user's HADOOP_CLASSPATH.  Therefore there is no way to put your own JARs in front of those that the hadoop wrapper script sets.
> We propose a patch that reverses this order.  Failing that, we would like to add a command line option to override this behavior and enable a user's JARs to be found before the wrong ones in the Hadoop library paths.
> We always welcome your opinions.



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