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On Fri, Feb 12, 2016, at 01:45 PM, John Garbutt wrote:
> On 12 February 2016 at 18:17, Andrew Laski <andrew at lascii.com> wrote:
> >
> >
> > On Fri, Feb 12, 2016, at 12:15 PM, Matt Riedemann wrote:
> >> Forgive me for thinking out loud, but I'm trying to sort out how nova
> >> would use a microversion in the nova API for the get-me-a-network
> >> feature recently added to neutron [1] and planned to be leveraged in
> >> nova (there isn't a spec yet for nova, I'm trying to sort this out for a
> >> draft).
> >>
> >> Originally I was thinking that a network is required for nova boot, so
> >> we'd simply check for a microversion and allow not specifying a network,
> >> easy peasy.
> >>
> >> Turns out you can boot an instance in nova (with neutron as the network
> >> backend) without a network. All you get is a measly debug log message in
> >> the compute logs [2]. That's kind of useless though and seems silly.
> >>
> >> I haven't tested this out yet to confirm, but I suspect that if you
> >> create a nova instance w/o a network, you can latter try to attach a
> >> network using the os-attach-interfaces API as long as you either provide
> >> a network ID *or* there is a public shared network or the tenant has a
> >> network at that point (nova looks those up if a specific network ID
> >> isn't provided).
> >>
> >> The high-level plan for get-me-a-network in nova was simply going to be
> >> if the user tries to boot an instance and doesn't provide a network, and
> >> there isn't a tenant network or public shared network to default to,
> >> then nova would call neutron's new auto-allocated-topology API to get a
> >> network. This, however, is a behavior change.
> >>
> >> So I guess the question now is how do we handle that behavior change in
> >> the nova API?
> >>
> >> We could add an auto-create-net boolean to the boot server request which
> >> would only be available in a microversion, then we could check that
> >> boolean in the compute API when we're doing network validation.
> >>
> >
> > I think a flag like this is the right approach. If it's currently valid
> > to boot an instance without a network than there needs to be something
> > to distinguish a request that wants a network created vs. a request that
> > doesn't want a network.
> >
> > This is still hugely useful if all that's required from a user is to
> > indicate that they would like a network, they still don't need to
> > understand/provide details of the network.
> 
> I was thinking a sort of opposite. Would this work?
> 
> We add a new micro-version that does this:
> * nothing specified: do the best we can to get a port created
> (get-me-a-network, etc,), or fail if not possible
> * --no-nics option (or similar) that says "please don't give me any nics"
> 
> This means folks that don't want a network, reliably have a way to do
> that. For everyone else, we do the same thing when using either
> neutron or nova-network VLAN manager.

I think this pushes our microversions meaning a bit further than
intended. I don't think the API should flip behaviors simply based on a
microversion.

What about requiring nic information with the microversion? Make users
indicate explicitly if they want a network or not and avoid changing a
default behavior.


> 
> Thanks,
> johnthetubaguy
> 
> PS
> I think we should focus on the horizon experience, CLI experience, and
> API experience separately, for a moment, to make sure each of those
> cases actually works out OK.
> 
> >> Today if you don't specify a network and don't have a network available,
> >> then the validation in the API is basically just quota checking that you
> >> can get at least one port in your tenant [3]. With a flag on a
> >> microversion, we could also validate some other things about
> >> auto-creating a network (if we know that's going to be the case once we
> >> hit the compute).
> >>
> >> Anyway, this is mostly me getting thoughts out of my head before the
> >> weekend so I don't forget it and am looking for other ideas here or
> >> things I might be missing.
> >>
> >> [1] https://blueprints.launchpad.net/neutron/+spec/get-me-a-network
> >> [2]
> >> https://github.com/openstack/nova/blob/30ba0c5eb19a9c9628957ac8e617ae78c0c1fa84/nova/network/neutronv2/api.py#L594-L595
> >> [3]
> >> https://github.com/openstack/nova/blob/30ba0c5eb19a9c9628957ac8e617ae78c0c1fa84/nova/network/neutronv2/api.py#L1107
> >>
> >> --
> >>
> >> Thanks,
> >>
> >> Matt Riedemann
> >>
> >>
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