[jira] [Resolved] (YARN-4353) Provide short circuit user group mapping for NM/AM

["Daniel Templeton (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/YARN-4353?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daniel Templeton resolved YARN-4353.
------------------------------------
      Resolution: Won't Fix
    Hadoop Flags: Reviewed

I'm fine with closing this out.  I added {{NullGroupsMapping}} in order to resolve this JIRA, but I never felt confident enough to pull the trigger.

> Provide short circuit user group mapping for NM/AM
> --------------------------------------------------
>
>                 Key: YARN-4353
>                 URL: https://issues.apache.org/jira/browse/YARN-4353
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: nodemanager
>    Affects Versions: 2.7.1
>            Reporter: Daniel Templeton
>            Assignee: Daniel Templeton
>            Priority: Major
>         Attachments: YARN-4353.prelim.patch
>
>
> When the NM launches an AM, the {{ContainerLocalizer}} gets the current user from {{UserGroupInformation}}, which triggers user group mapping, even though the user groups are never accessed.  If secure LDAP is configured for group mapping, then there are some additional complications created by the unnecessary group resolution.  Additionally, it adds unnecessary latency to the container launch time.
> To address the issue, before getting the current user, the {{ContainerLocalizer}} should configure {{UserGroupInformation}} with a null group mapping service that quickly and quietly returns an empty group list for all users.



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