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https://issues.apache.org/jira/browse/MAPREDUCE-3162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13124701#comment-13124701
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Todd Lipcon commented on MAPREDUCE-3162:
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bq. More of the init used to be per-application, before changing the 
localization to be per-container

The issue that got me looking at this code was MAPREDUCE-3159 -- a place where 
the per-application action of rming the appcachedir was actually being run on 
every container. But it makes sense that we can avoid the shell-out to the 
localizer on every container initialization - it's not super expensive but the 
fork isn't free either. In the case that a container has no new resources 
associated with it, we shouldn't need to spawn one, right?
                
> Separate application-init and container-init event types in NM's 
> ApplicationImpl FSM
> ------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-3162
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3162
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>    Affects Versions: 0.23.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>         Attachments: mr-3162.txt
>
>
> Currently, the ApplicationImpl receives an INIT_APPLICATION event on every 
> container initialization. Only on the first one does it really mean to init 
> the application, whereas all subsequent events are for specific containers. 
> This JIRA is to separate the events into INIT_APPLICATION, sent once and only 
> once per application, and INIT_CONTAINER, which is sent for every container. 
> The first container sends INIT_APPLICATION followed by INIT_CONTAINER.

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