[openstack-dev] [nova][neutron] How would nova microversion get-me-a-network in the API?
mriedem at linux.vnet.ibm.com
Fri Feb 12 17:15:14 UTC 2016
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  and planned to be leveraged in
nova (there isn't a spec yet for nova, I'm trying to sort this out for a
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,
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 . 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
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.
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 . 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.
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