Allen Wittenauer commented on YARN-2495:

bq. while modifying the script he will be able to configure the valid labels 

The script can be updated *independently* of changing the running configuration 
files.  Changing the xml comfigs will also require a *coordinated* reconfigure 
of the RM.  That isn't realistic, especially for things such as rolling 
upgrades. HARM, of course, makes the situation even worse. Additionally, I'm 
sure the label validation code will spam the RM logs every time it gets an 
invalid label, which is pretty much a "please fill the log directory" action.

The *only* scenario I can think of where label validation has a practical use 
is if AMs and/or containers are allowed to inject labels.  But that should be a 
different control structure altogether and have zero impact on administrator 
controlled labels.

bq. Seems like maintenance wise it might become difficult for example,

Label validation actually makes your example worse because now the labels 
disappear completely.  Is it a problem with the script or is it a problem with 
the label definition?

bq.  i feel centralized Label validation can be made configurable. Please 
provide opinion on this.

Just disable it completely.  I'm still waiting to hear what practical 
application this bug would have.

> Allow admin specify labels in each NM (Distributed configuration)
> -----------------------------------------------------------------
>                 Key: YARN-2495
>                 URL: https://issues.apache.org/jira/browse/YARN-2495
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: resourcemanager
>            Reporter: Wangda Tan
>            Assignee: Naganarasimha G R
> Target of this JIRA is to allow admin specify labels in each NM, this covers
> - User can set labels in each NM (by setting yarn-site.xml or using script 
> suggested by [~aw])
> - NM will send labels to RM via ResourceTracker API
> - RM will set labels in NodeLabelManager when NM register/update labels

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