Open Stack

On Sat, Aug 18, 2018 at 8:25 AM Chris Dent <cdent+os at anticdent.org> wrote:

>
> 5. In OpenStack we have a tradition of the contributors having a
> strong degree of self-determination. If that tradition is to be
> upheld, then it would make sense that the people who designed and
> wrote the code that is being extracted would get to choose what
> happens with it. As much as Mel's and Dan's (only picking on them
> here because they are the dissenting voices that have showed up so
> far) input has been extremely important and helpful in the evolution
> of placement, they are not those people.
>
> 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.
>
> Thank you.
>

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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