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From Lei Guo <lei...@huawei.com>
Subject RE: Node Label, partition or an attribute of node?
Date Thu, 25 Jun 2015 20:27:23 GMT
Hi, Wangda,

Actually, it's the two types of node label causing the confusion for me. For a scheduling
system, it's to find the best match between "resource" and "workload" via different "policies".
Both node partition and node constraints are scheduling policies. The node label should be
part of resource (as an attribute), and be used in two different policies. If we position
the node label this way, there is only one type of node label. This is related to how we define/abstract
"resource" in Yarn. Currently, only CPU/memory (extending with disk/network bandwidth) considered
as resource for a node. As you mentioned in Summit slides, GPU could also be a resource. These
are all consumable resources/attributes provided by node while node label is non-consumable
resource/attribute provided by a node. 

Lei

-----Original Message-----
From: Wangda Tan [mailto:wheeleast@gmail.com] 
Sent: Thursday, June 25, 2015 3:51 PM
To: yarn-dev@hadoop.apache.org
Subject: Re: Node Label, partition or an attribute of node?

Hi Lei,
To clarify, node label has two types, one is node partition, which is
supported already. Another is node constraint (you can also call it node
attribute), which is still under design. Both of them are string typed.

And node label (including partition and attribute), can be either
per-application level and per-container level, this is supported by API
already.

And you can take a look at my summit slides:
http://www.slideshare.net/Hadoop_Summit/node-labels-in-yarn-49792443. Which
may help you better understand partition / constraint and relationship
between them.

Thanks,
Wangda

On Thu, Jun 25, 2015 at 12:34 PM, Lei Guo <leiguo@huawei.com> wrote:

> The definition of label in YARN-796 is pretty clear,
>
> *         Node Label  label that describes a node. Node can have multiple
> labels
>
> *         Label expression  logical combination of labels (using &&  and,
> ||  or, !  not)
> With this definition (without considering the implementation), a node
> label could be treated as a Boolean type attribute of a node. Assuming the
> administrator define label1, label2, label3 in the system, and associate
> node1 with "label1, label2", this means the value of attribute label1 and
> label2 for node1 is true, while the value of attribute label3 will be false
> for node1.
>
> In current Yarn implementation, seems the resource partitioning has been
> treated as the primary use case for node label, and some
> design/implementation of node label mainly consider on the partitioning
> case, even the multiple label support has been disabled in  YARN-2694. To
> cover the workload resource request use case, YARN-3409 was proposed while
> the description/example of constraint node label in YARN-3409 seems more
> like a String type attribute for a node instead of Boolean type anymore. I
> got confused about node label.
>
> From my view, node label is one attribute of a node, and it could be used
> for different scheduling scenarios. No matter resource partitioning or job
> scheduling constraints, a node label is just a label on a node. For
> partitioning, we can have one object calling partition or resource group
> representing the group of nodes with certain label; for workload scheduling
> constraints purpose, we may want to extend the current application level
> constraint to be container level constraint, for one application, the
> master may request one type of resource while the slave request another
> type of resource.
>
> Comments?
>
> Lei Guo
> Senior Architect, Huawei Canada Research Centre
>
>
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