[jira] [Commented] (YARN-10607) User environment is unable to prepend PATH when mapreduce.admin.user.env also sets PATH

["Eric Badger (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-10607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17278356#comment-17278356 ] 

Eric Badger commented on YARN-10607:
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Patch 001 adds a new config parameter called {{yarn.nodemanager.force.path}}. The content of this config parameter will be force prepended to the PATH of all containers. 

Also not that it is imperative to use {{PATH}} instead of $PATH if you want to expand the path of the container environment and not the path of the client

> 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
>
>
> 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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