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https://issues.apache.org/jira/browse/YARN-3367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15070715#comment-15070715
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Sangjin Lee commented on YARN-3367:
-----------------------------------

I haven't fully digested the code so I might be off-base. But when I see 
variables such as stopped, waitForDrained, and drained along with the thread 
and the queue, it feels rather like reinventing the wheel. Also, I see two sets 
of wait-notify pairs. Using the executor service should take care of the need 
for using those, and hopefully we can wrap the code between taking the item off 
of the queue and looping back into a callable/runnable.

> Replace starting a separate thread for post entity with event loop in 
> TimelineClient
> ------------------------------------------------------------------------------------
>
>                 Key: YARN-3367
>                 URL: https://issues.apache.org/jira/browse/YARN-3367
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: timelineserver
>    Affects Versions: YARN-2928
>            Reporter: Junping Du
>            Assignee: Naganarasimha G R
>              Labels: yarn-2928-1st-milestone
>         Attachments: YARN-3367-feature-YARN-2928.003.patch, 
> YARN-3367-feature-YARN-2928.v1.002.patch, 
> YARN-3367-feature-YARN-2928.v1.004.patch, YARN-3367.YARN-2928.001.patch
>
>
> Since YARN-3039, we add loop in TimelineClient to wait for 
> collectorServiceAddress ready before posting any entity. In consumer of  
> TimelineClient (like AM), we are starting a new thread for each call to get 
> rid of potential deadlock in main thread. This way has at least 3 major 
> defects:
> 1. The consumer need some additional code to wrap a thread before calling 
> putEntities() in TimelineClient.
> 2. It cost many thread resources which is unnecessary.
> 3. The sequence of events could be out of order because each posting 
> operation thread get out of waiting loop randomly.
> We should have something like event loop in TimelineClient side, 
> putEntities() only put related entities into a queue of entities and a 
> separated thread handle to deliver entities in queue to collector via REST 
> call.



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