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Boris
       I think you in fact covered two topic, one is if use db or rpc for communication. This has been discussed a lot. But I didn't find the conclusion. From the discussion,  seems the key thing is the fan out messages. I'd suggest you to bring this to scheduler sub meeting.

http://eavesdrop.openstack.org/meetings/scheduler/2013/scheduler.2013-06-11-14.59.log.html
http://www.mail-archive.com/openstack-dev@lists.openstack.org/msg00070.html
http://comments.gmane.org/gmane.comp.cloud.openstack.devel/23

       The second topic is adding extra tables to compute nodes. I think we need the lazy loading for the compute node, and also I think with object model, we can further improve it if we utilize the compute node object.

Thanks
--jyh


From: Boris Pavlovic [mailto:boris at pavlovic.me]
Sent: Friday, July 19, 2013 10:07 AM
To: OpenStack Development Mailing List
Subject: Re: [openstack-dev] [Nova] New DB column or new DB table?

Hi all,

We have to much different branches about scheduler (so I have to repeat here also).

I am against to add some extra tables that will be joined to compute_nodes table on each scheduler request (or adding large text columns).
Because it make our non scalable scheduler even less scalable.

Also if we just remove DB between scheduler and compute nodes we will get really good improvement in all aspects (performance, db load, network traffic, scalability )
And also it will be easily to use another resources provider (cinder, ceilometer e.g..) in Nova scheduler.

And one more thing this all could be really simple implement in current Nova, without big changes
 https://docs.google.com/document/d/1_DRv7it_mwalEZzLy5WO92TJcummpmWL4NWsWf0UWiQ/edit?usp=sharing


Best regards,
Boris Pavlovic

Mirantis Inc.

On Fri, Jul 19, 2013 at 8:44 PM, Dan Smith <dms at danplanet.com<mailto:dms at danplanet.com>> wrote:
> IIUC, Ceilometer is currently a downstream consumer of data from
> Nova, but no functionality in Nova is a consumer of data from
> Ceilometer. This is good split from a security separation point of
> view, since the security of Nova is self-contained in this
> architecture.
>
> If Nova schedular becomes dependant on data from ceilometer, then now
> the security of Nova depends on the security of Ceilometer, expanding
> the attack surface. This is not good architecture IMHO.
Agreed.

> At the same time, I hear your concerns about the potential for
> duplication of stats collection functionality between Nova &
> Ceilometer. I don't think we neccessarily need to remove 100% of
> duplication. IMHO probably the key thing is for the virt drivers to
> expose a standard API for exporting the stats, and make sure that
> both ceilometer & nova schedular use the same APIs and ideally the
> same data feed, so we're not invoking the same APIs twice to get the
> same data.
I imagine there's quite a bit that could be shared, without dependency
between the two. Interfaces out of the virt drivers may be one, and the
code that boils numbers into useful values, as well as perhaps the
format of the JSON blobs that are getting shoved into the database.
Perhaps a ceilo-core library with some very simple primitives and
definitions could be carved out, which both nova and ceilometer could
import for consistency, without a runtime dependency?

--Dan

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