[openstack-dev] [all] [nova] [placement] placement below or beside compute after extraction?

Jay Pipes jaypipes at gmail.com
Mon Aug 20 11:52:46 UTC 2018


On 08/18/2018 08:25 AM, Chris Dent wrote:
> So my hope is that (in no particular order) Jay Pipes, Eric Fried,
> Takashi Natsume, Tetsuro Nakamura, Matt Riedemann, Andrey Volkov,
> Alex Xu, Balazs Gibizer, Ed Leafe, and any other contributor to
> placement whom I'm forgetting [1] would express their preference on
> what they'd like to see happen.
> 
> At the same time, if people from neutron, cinder, blazar, zun,
> mogan, ironic, and cyborg could express their preferences, we can get
> through this by acclaim and get on with getting things done.

I am not opposed to extracting the placement service into its own repo. 
I also do not view it as a priority that should take precedence over the 
completion of other items, including the reshaper effort and the 
integration of placement calls into Nova (nested providers, sharing 
providers, etc).

The remaining items are Nova-centric. We need Nova-focused contributors 
to make placement more useful to Nova, and I fail to see how extracting 
the placement service will meet that goal. In fact, one might argue, as 
Melanie implies, that extracting placement outside of the Compute 
project would increase the velocity of the placement project *at the 
expense of* getting things done in the Nova project.

We've shown we can get many things done in placement. We've shown we can 
evolve the API fairly quickly. The velocity of the placement project 
isn't the problem. The problem is the lag between features being written 
into placement (sometimes too hastily IMHO) and actually *using* those 
features in Nova.

As for the argument about other projects being able (or being more 
willing to) use placement, I think that's not actually true. The 
projects that might want to ditch their own custom resource tracking and 
management code (Cyborg, Neutron, Cinder, Ironic) have either already 
done so or would require minimal changes to do that. There are no 
projects other than Ironic that I'm aware of that are interested in 
using the allocation candidates functionality (and the allocation claim 
process that entails) for the rough scheduling functionality that 
provides. I'm not sure placement being extracted would change that.

Would extracting placement out into its own repo result in a couple more 
people being added to the new placement core contributor team? Possibly. 
Will that result in Nova getting the integration pieces written that 
make use of placement? No, I don't believe so.

So, I'm on the fence. I understand the desire for separation, and I'm 
fully aware of my bias as a current Nova core contributor. I even 
support the process of extracting placement. But do I think it will do 
much other than provide some minor measure of independence? No, not really.

Consider me +0.

Best,
-jay



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