[openstack-dev] Custom Nova scheduler based on CPU queue length

Clint Byrum clint at fewbar.com
Wed Oct 21 07:04:46 UTC 2015

Excerpts from Rahul Nair's message of 2015-10-20 18:53:09 -0700:
> ​Hi All,
> I am fairly new to the OpenStack community and is trying to create a custom
> scheduler for Nova. A scheduler based on CPU queue length. Kindly apologize
> if there are any inaccuracies in my statements.
> As I understand a weigher for the filter scheduler that weighs filtered
> host machines based on the host weight option, 'cpu.percent' can be
> configured to prioritize the hosts based on CPU percentage, but there are
> only limited options when it comes to filtering of machines in the first
> place, that too using the CPU queue length.
> Also, I understand that IBM has its platform resource scheduler that can be
> used to build custom plugins to get user defined metrics, is there a
> similar way in pure Openstack which can be used to get the CPU queue length.
> As of now, I am thinking of writing a custom script to be kept in all
> compute nodes to retrieve the CPU queue length and send it to the Nova
> controller, is this the way to go, or is there a defined approach that I
> can follow to implement a scheduler that uses CPU queue length to filter
> physical machines.
> Any pointers on this would be really helpful.

Rahul, I'm realy curious about what it is you're trying to accomplish

The CPU queue length is an extremely volatile statistic. Is this maybe
for a single-purpose cloud where you do have some idea what might be

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