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From Arun C Murthy <...@hortonworks.com>
Subject Re: meaning or usage of reserved containers in YARN Capacity scheduler
Date Mon, 24 Feb 2014 22:56:27 GMT
Apologies for the late reply.

The concept of reservation is used to prevent starvation.

For e.g. let's say you have 2 machines with 8G each. Now each of those are running containers
which take up 6G on nodeA and 7G on nodeB.

Another application comes in and then asks for a single container of 4G, which can't be allocated
anywhere in the cluster. In this case (e.g.) 4G is reserved on nodeA and is given to the app
only when it's available… else, this application would be 'starved' if other apps came in
and asked for 1G or 2G and would hence, 4G would never be freed up.

Hope that helps.


On Feb 7, 2014, at 7:58 AM, ricky l <rickylee0815@gmail.com> wrote:

> Hi all,
> I have a question about reserved containers in the YARN capacity
> scheduler. After reading the source code and related document, it is
> not very clear. What is the purpose or practical usage of the reserved
> container? thx.

Arun C. Murthy
Hortonworks Inc.

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