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https://issues.apache.org/jira/browse/YARN-3049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14652206#comment-14652206
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Zhijie Shen commented on YARN-3049:
-----------------------------------

Hi Sangjin,


Thanks for your comments. The proposed method will work for now and can 
minimize the change we should make. In fact, I used to think of this method 
too. The reason why I abandoned it is that the method couple the business logic 
and data storage. It potentially increase the risk that the change in the 
business logic will break the storage layer. For example, we rename app_created 
as app_started. This may be still easy to fix, but the maintenance difficulty 
is likely to increase as logic grows more complex. That's why I think we should 
let app collector to tell the backend that it's the first request.


On the other side, I agree RM should be responsible for this too. Actually this 
is also what I did in the current patch. If you think my proposal of letting 
app collector to determine if it is the first request, the way we can do is to 
extend RM app collector and implement this logic there.


Thanks,

Zhijie



> [Storage Implementation] Implement storage reader interface to fetch raw data 
> from HBase backend
> ------------------------------------------------------------------------------------------------
>
>                 Key: YARN-3049
>                 URL: https://issues.apache.org/jira/browse/YARN-3049
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>            Reporter: Sangjin Lee
>            Assignee: Zhijie Shen
>         Attachments: YARN-3049-WIP.1.patch, YARN-3049-WIP.2.patch, 
> YARN-3049-WIP.3.patch, YARN-3049-YARN-2928.2.patch, 
> YARN-3049-YARN-2928.3.patch, YARN-3049-YARN-2928.4.patch
>
>
> Implement existing ATS queries with the new ATS reader design.



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