[nova] review guide for the bandwidth patches

Matt Riedemann mriedemos at gmail.com
Sat Jan 19 02:21:52 UTC 2019

On 1/18/2019 12:40 PM, Dan Smith wrote:
> Having a microversion that allows move operations for an instance
> configured with one of these ports seems really terrible to me.

I agree with that sentiment.

> Can we not return 403 in Stein, since moving instances is disable-able
> anyway, and just make it work in Train? Having a new microversion with a
> description of "nothing changed except we finished a feature so you can
> do this very obscure thing now" seems like we're just using them as an
> experimental feature flag, which was definitely not the intent. I know
> returning 403 for "you can't do this right now" isn't*as*  discoverable,
> but you kinda have to handle 403 for operations that could be disabled
> anyway, so...

We didn't discuss it too much on the call, but in thinking about it 
afterward, I think I would be OK with treating this like a bug fix in 
Train. We can fail move operations until we support this, and then once 
we support it, we just do, without a microversion. As noted, clients 
have to deal with this kind of stuff already, and I don't remember 
saying when we support live migration with NUMA (which now fails unless 
configured otherwise) that we would add a microversion for that - it 
either just works or it doesn't.

So I'm OK with not adding a second microversion for move operation 
support later.




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