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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HADOOP-12930) [Umbrella] Dynamic subcommands for hadoop shell scripts
Date Thu, 05 May 2016 18:14:12 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12930?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15199481#comment-15199481
] 

Allen Wittenauer edited comment on HADOOP-12930 at 5/5/16 6:14 PM:
-------------------------------------------------------------------

It is extremely desirable to be able to add subcommands to the hadoop, etc, commands dynamically.
There are several reasons to do this:

* Enable local variants of subcommands without worrying about breaking existing scripts. 
For example, distcp has historically been replaced with local versions for various reasons.
* Allows for greater testing capabilities
* Possibility of 3rd party/external-to-hadoop being allowed to add capabilities and take advantage
of the rich shell environment

Enabling this is relatively trivial:
* look for a function defined with a given pattern that matches the subcommand passed via
the CLI
* if that function exists, execute it with passed parameters
* if that function doesn't exist, continue on with our normal processing

In order to accomplish this, a few things need to take place:
* re-arrange the existing commands a bit for legibility/flexibility
* make some shell-local globals to be 'safe' globals that can span past their borders
* define an API by which 3rd parties may add and override existing commands
* get HADOOP-12857 committed for some pre-work


was (Author: aw):
It is extremely desirable to be able to add subcommands to the hadoop, etc, commands dynamically.
There are several reasons to do this:

* Enable local variants of subcommands without worrying about breaking existing scripts. 
For example, distcp has historically been replaced with local versions for various reasons.
* Allows for greater testing capabilities
* Possibility of 3rd party/external-to-hadoop being allowed to add capabilities and take advantage
of the rich shell environment

In order to accomplish this, a few things need to take place:
* re-arrange the existing commands a bit for legibility/flexibility
* make some shell-local globals to be 'safe' globals that can span past their borders
* define an API by which 3rd parties may add and override existing commands
* get HADOOP-12857 committed for some pre-work

> [Umbrella] Dynamic subcommands for hadoop shell scripts
> -------------------------------------------------------
>
>                 Key: HADOOP-12930
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12930
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: scripts
>    Affects Versions: 3.0.0
>            Reporter: Allen Wittenauer
>            Assignee: Allen Wittenauer
>            Priority: Critical
>
> Umbrella for converting hadoop, hdfs, mapred, and yarn to allow for dynamic subcommands.
See first comment for more details.



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