[openstack-dev] [nova] [placement] experimenting with extracting placement

Eoghan Glynn eglynn at redhat.com
Mon Mar 13 14:02:26 UTC 2017

> > We are close to the first milestone in Pike, right ? We also have
> > priorities for Placement that we discussed at the PTG and we never
> > discussed about how to cut placement during the PTG.
> >
> > Also, we haven't discussed yet with operators about how they would like
> > to see Placement being cut. At least, we should wait for the Forum about
> > that.
> >
> > For the moment, only operators using Ocata are using the placement API
> > and we know that most of them had problems when using it. Running for
> > cutting Placement in Queens would then mean that they would only have
> > one stable cycle after Ocata for using it.
> > Also, discussing at the above would then mean that we could punt other
> > disucssions. For example, I'd prefer to discuss how we could fix the
> > main problem we have with the scheduler about scheduler claims *before*
> > trying to think on how to cut Placement.
> It's definitely good to figure out what challenges people were having in
> rolling things out and document them, to figure out if they've been
> addressed or not. One key thing seemed to be not understanding that
> services need to all be registered in the catalog before services beyond
> keystone are launched. There is also probably a keystoneauth1 fix for
> this make it a softer fail.
> The cut over can be pretty seamless. Yes, upgrade scenarios need to be
> looked at. But that's honestly not much different from deprecating
> config options or making new aliases. It should be much less user
> noticable than the newly required cells v2 support.
> The real question to ask, now that there is a well defined external
> interface, will evolution of the Placement service stack, and addressing
> bugs and shortcomings related to it's usage, work better as a dedicated
> core team, or inside of Nova. My gut says Queens is the right time to
> make that split, and to start planning for it now.

>From a downstream perspective, I'd prefer to see a concentration on
deriving *user-visible* benefits from placement before incurring more
churn with an extraction (given the proximity to the churn on
deployment tooling from the scheduler decision-making cutover to
placement at the end of ocata).

Just my $0.02 ...


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