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https://issues.apache.org/jira/browse/HADOOP-9450?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13622847#comment-13622847
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Mitch Wyle commented on HADOOP-9450:
------------------------------------
Thanks for the detailed and quick reply, Chris!
The issue is that in all cases the HADOOP_CLASSPATH is appended to existing
CLASSPATH instead of prepended to pick up Users' JARS first. If some class in
a JAR is already there, users cannot put their own FIRST.
{noformat}
# add user-specified CLASSPATH last
if [ "$HADOOP_USER_CLASSPATH_FIRST" = "" ] && [ "$HADOOP_CLASSPATH" != "" ];
then
CLASSPATH=${CLASSPATH}:${HADOOP_CLASSPATH}
fi
{noformat}
...should be:
{noformat}
# add user-specified CLASSPATH last
if [ "$HADOOP_USER_CLASSPATH_FIRST" = "" ] && [ "$HADOOP_CLASSPATH" != "" ];
then
CLASSPATH=${HADOOP_CLASSPATH}:${CLASSPATH}
fi
{noformat}
> 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: Bug
> Reporter: Mitch Wyle
>
> 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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