Open Stack

> If feels like the right sequence is:
> 
> -          Deploy the new code in Nova and at the same time set
> vif_plugging_is-fatal=False, so that Nova will wait for Neutron, but
> will still continue if the event never turns up (which is kind of like
> the code was before, but with a wait)

Yes, but set the timeout=0. This will cause nova to gracefully accept
the events when they start showing up, but the computes will not wait
for them.

> -          Then update Neutron (with presumably some additional config)
> so that it starts sending events

Right, after that, set fatal=True and timeout=300 (or whatever) and
you're good to go.

> Is that right, and any reason why the default for vif_plugging_is_fatal
> shouldn’t be False insated of True to make this sequence less dependent
> on matching config changes ?

Yes, because the right approach to a new deployment is to have this
enabled. If it was disabled by default, most deployments would never
turn it on.

--Dan