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https://issues.apache.org/jira/browse/YARN-10607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17279810#comment-17279810
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Jim Brennan commented on YARN-10607:
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Thanks for the updates [~ebadger]. +1 This looks good to me.
I will commit today.
> User environment is unable to prepend PATH when mapreduce.admin.user.env also
> sets PATH
> ---------------------------------------------------------------------------------------
>
> Key: YARN-10607
> URL: https://issues.apache.org/jira/browse/YARN-10607
> Project: Hadoop YARN
> Issue Type: Bug
> Reporter: Eric Badger
> Assignee: Eric Badger
> Priority: Major
> Attachments: YARN-10607.001.patch, YARN-10607.002.patch,
> YARN-10607.003.patch, YARN-10607.004.patch, YARN-10607.004.patch
>
>
> When using the tarball approach to ship relevant Hadoop jars to containers,
> it is helpful to set {{mapreduce.admin.user.env}} to something like
> {{PATH=./hadoop-tarball:\{\{PATH\}\}}} to make sure that all of the Hadoop
> binaries are on the PATH. This way you can call {{hadoop}} instead of
> {{./hadoop-tarball/hadoop}}. The intention here is to force prepend
> {{./hadoop-tarball}} and then append the set {{PATH}} afterwards. But if a
> user would like to override the appended portion of {{PATH}} in their
> environment, they are unable to do so. This is because {{PATH}} ends up
> getting parsed twice. Initially it is set via {{mapreduce.admin.user.env}} to
> {{PATH=./hadoop-tarball:$SYS_PATH}}}. In this case {{SYS_PATH}} is what I'll
> refer to as the normal system path. E.g. {{/usr/local/bin:/usr/bin}}, etc.
> After this, the user env parsing happens. For example, let's say the user
> sets their {{PATH}} to {{PATH=.:$PATH}}. We have already parsed {{PATH}} from
> the admin.user.env. Then we go to parse the user environment and find the
> user also specified {{PATH}}. So {{$PATH}} ends up getting getting expanded
> to {{./hadoop-tarball:$SYS_PATH}}, which leads to the user's {{PATH}} being
> {{PATH=.:./hadoop-tarball:$SYS_PATH}}. We then append this to {{PATH}}, which
> has already been set in the environment map via the admin.user.env. So we
> finally end up with
> {{PATH=./hadoop-tarball:$SYS_PATH:.:./hadoop-tarball:$SYS_PATH}}.
> This normally isn't a huge deal, but if you want to ship a version of
> python/perl/etc. that clashes with the one that is already there in
> {{SYS_PATH}}, you will need to refer to it by its full path. Since in the
> above example, {{.}} doesn't appear until after {{$SYS_PATH}}. This is a pain
> and it should be possible to prepend its {{PATH}} to override the
> system/container {{SYS_PATH}}, even when also forcefully prepending to
> {{PATH}} with you hadoop tarball.
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