Hi Sylvain,

Thanks for the clarification, I'd missed that it was where the public network 
belonged to the same tenant (it's not a use case we run with).

So I can see that option [1] would make the validation work by (presumably) not 
including the shared network in the list of networks,  but looking further into 
the code allocate_for_instance() uses the same call to decide which networks it 
needs to create ports for, and from what I can see it would attach the instance 
to both networks.

https://github.com/openstack/nova/blob/master/nova/network/neutronv2/api.py#L244

However that feels like the same problem that the patch was originally trying 
to fix, in that the network order isn't controlled by the user, and many Guest 
OS's will only configure the first NIC they are presented with.  The idea was 
that in this case the user needs to explicitly specify the networks in the 
order that they want them to be attached to.

Am I still missing something ?

Cheers,
Phil



From: Sylvain Bauza [mailto:[email protected]]
Sent: 24 January 2014 14:02
To: OpenStack Development Mailing List (not for usage questions)
Cc: Day, Phil
Subject: Re: [openstack-dev] [Nova] Why Nova should fail to boot if there are 
only one private network and one public network ?

Hi Phil,

Le 24/01/2014 14:13, Day, Phil a écrit :
HI Sylvain,

The change only makes the user have to supply a network ID if there is more 
than one private network available (and the issue there is that otherwise the 
assignment order in the Guest is random, which normally leads to all sorts of 
routing problems).

I'm sorry, but the query also includes shared (so, public) networks from the 
same tenant. See [1].



I'm running a standard Devstack with Neuron (built from trunk a couple of days 
ago), can see both a private and public network, and can boot VMs without 
having to supply any network info:


Indeed, that does work because Devstack is smart enough for creating the two 
networks with distinct tenant_ids. See [2] as a proof :-)
If someone is building a private and a public network *on the same tenant*, it 
will fail to boot. Apologies if I was unclear.

So, the question is : what shall I do for changing this ? There are 2 options 
for me:
 1. Add an extra param to _get_available_networks : shared=True and only return 
shared networks if the param is set to True (so we keep compatibility with all 
the calls)
 2. Parse the nets dict here [3] to expurge the shared networks when len(nets) 
> 1. That's simple but potentially a performance issue, as it's O(N).

I would personnally vote for #1 and I'm ready to patch. By the way, the test 
case needs also to be updated [4].

-Sylvain


[1] 
https://github.com/openstack/nova/blob/master/nova/network/neutronv2/api.py#L127
[2] : http://paste.openstack.org/show/61819/
[3] : 
https://github.com/openstack/nova/blob/master/nova/network/neutronv2/api.py#L528
[4] : 
https://github.com/openstack/nova/blob/master/nova/tests/network/test_neutronv2.py#L1028
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