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From Xuan Gong <xg...@hortonworks.com>
Subject Re: question about when do resource matching in YARN
Date Fri, 20 Sep 2013 15:56:53 GMT
Hey, Wei:
      The nodeHeartBeat is used to let RM knows this NM is still alive. We
only assign containers from alive NM. Another thing is when scheduler
receives the nodeHeartBeat, the scheduler will get the container status
(such as completed, new launched) from NM, and it can use it to update the
resource.

       You can take a look those source codes, it can help you understand
better.
1. NodeStatusUpdaterImpl::startStatusUpdater(). it used to send out the
nodeheartbeat
2. ResourceTrackerService::nodeHeartbeat(). This one is used to get
heartbeat from NM, and send to RMNodeImpl
3. RMNodeImpl::StatusUpdateWhenHealthyTransition().  Get the heartBeat, and
do locally update.
4. CapacityScheduler::nodeUpdate(). Processing the heartbeat info, and
potentially assign containers.

Thanks

Xuan


On Fri, Sep 20, 2013 at 7:17 AM, wei yan @ Gmail <ywskycn@gmail.com> wrote:

> Hi, all,
>
> I have a simple question. Currently in YARN, the resource matching is
> triggered by the node manager heartbeat. That is, assignContainers() is
> only invoked when a new heartbeat comes in. Why we don't use resource
> request triggered mechanism? That is, when AM submits allocateRequest, we
> do the resource matching and assign containers.
>
> Does anybody have any idea about this?
>
> thanks,
> Wei

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