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https://issues.apache.org/jira/browse/IMPALA-11027?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Amogh Margoor resolved IMPALA-11027.
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Resolution: Fixed
> Support for ShellBasedUnixGroupMapping for Impala's user delegation via groups
> ------------------------------------------------------------------------------
>
> Key: IMPALA-11027
> URL: https://issues.apache.org/jira/browse/IMPALA-11027
> Project: IMPALA
> Issue Type: Improvement
> Reporter: Amogh Margoor
> Assignee: Amogh Margoor
> Priority: Major
>
> When impala.doAs.user is set for user delegation, Impala checks if the
> delegation is allowed or not based on either of the following:
> # user mapping: Specified using
> {code:java}
> authorized_proxy_user_config{code}
> # groups mapping: Specified using. authorized_proxy_group_config
>
>
> For checking group mapping currently JNIBasedUnixGroupMapping is supported
> and not ShellBasedUnixGroupMapping. Ref:
> [https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-common/GroupsMapping.html]
> This was done because of caveats that ShellBasedUnixGroupMapping spawns a new
> shell command to figure out groups for 'impala.doAs.user' when group mapping
> is specified. Many numerous shell commands could potentially cause issues
> like resource crunch, file descriptor issues and also zombie processes. Hence
> it is discouraged. However, we should support it for users that understand
> these caveats well and still want to use it. One reason could be that other
> components of impala might not have moved to JNI based group mapping and
> still be using Shell based.
> Regarding caveats few things help:
> # Chances are zombie process are very low.
> # Due to vfork being used we do not see too much of resource consumption
> during process spawning. On memory it takes around 8KB and duration of
> process is around 16-17ms.
> # immediate exec after vfork would ensure other resources that might get
> cloned via vfork are present for very short duration.
>
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