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This is great information, thanks Hongbin.

If I'm understanding correctly, it sounds like Zun ultimately wants to
be a peer of nova in terms of placement consumption. Using the resource
information reported by nova, neutron, etc., you wish to be able to
discover viable targets for a container deployment (GET
/allocation_candidates) and claim resources to schedule to them (PUT
/allocations/{uuid}). And you want to do it while Nova is doing the same
for VMs, in the same cloud. Do I have that right?

> * Is placement stable enough so that it won't break us often?

Yes.

> * If there is a breaking change in placement and we contribute a fix,
> how fast the fix will be merged?
> * If there is a feature request from our side and we contribute patches
> to placement, will the patches be accepted?

I believe this to be one of the main issues in the decision about
independent governance. If placement remains under nova, it is more
likely that fixes and features impacting the nova team would receive
higher priority than those impacting zun.

-efried

> I express the Zun's point of view.
> 
> Zun has a scheduler to schedule containers to nodes based on the
> demanded and available compute resources (i.e. cpu, memory). Right now,
> Zun's scheduler is independent of Nova so VMs and containers have to be
> separated into two set of resource pools. One of the most demanding
> features from our users (e.g. requested from Chinese UnionPay via
> OpenStack Financial WG) is to have VMs and containers share the same set
> of resource pool to maximize utilization. To satisfy this requirement,
> Zun needs to know the current resource allocation that are made by
> external services (i.e. Nova) so that we can take those information into
> account when scheduling the containers. Adopting placement is a
> straightforward and feasible approach to address that.
> 
> As a summary, below are high-level requirements from Zun's perspective:
> * Have VMs and containers multiplex into a pool of compute nodes.
> * Make optimal scheduling decisions for containers based on information
> (i.e. VM allocations) query from placement.
> * Report container allocations to placement and hope external schedulers
> can make optimal decisions.
> 
> We haven't figured out the technical details yet. However, to look
> forward, if Zun team decides to adopt placement, I would have the
> following concerns:
> * Is placement stable enough so that it won't break us often?
> * If there is a breaking change in placement and we contribute a fix,
> how fast the fix will be merged?
> * If there is a feature request from our side and we contribute patches
> to placement, will the patches be accepted?
> 
> Regardless of whether placement is extracted or not, above are the
> concerns that I mostly care about.
> 
> Best regards,
> Hongbin
> 
> 
> 
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