[nova][neutron][cyborg] Bandwidth (and accel) providers are broken if CONF.host is set

Bal√°zs Gibizer balazs.gibizer at est.tech
Thu Nov 28 08:54:06 UTC 2019

On Wed, Nov 27, 2019 at 17:03, Sean Mooney <smooney at redhat.com> wrote:
> On Wed, 2019-11-27 at 16:20 +0100, Bence Romsics wrote:
>>  > > resource_provider_hypervisors = br-physnet0:hypervisor0,...
>>  >
>>  > this also wont work as the same bridge name will exists on 
>> multipel hosts
>>  Of course the same bridge/nic name can exist on multiple hosts. And
>>  each report_state message is clearly belonging to a single agent and
>>  the configurations field is persisted per agent, so there won't be a
>>  collision ever.
> that is in the non iroinc smart nic case. in the ironic smart nic 
> case with the ovs super agent
> which is the only case where there would be multiple hypervisor 
> managed by the same
> agent the agent will be remote.

When you say "ironic smart nic case with the ovs super agent", do you 
refer to this abandoned spec [1]?

> so in the non ironic case it does not need to be a list.
> in the smartnic case it might need to be a list

In that spec the author proposes [2] not to break the 1-1 mapping 
between OVS agent and remote OVS. So as far as I see there is no need 
for a list in this case either.

> but a mapping of bridge or pyshnet wont be unique
> and a agent hostname (CONF.host) to hypervior host would be 1:N so 
> its not clear how you would select
> form the N RPs if all you know form nova is the binding host which is 
> the service host not hypervior hostname.

Are we talking about a problem during binding here? As this feels to be 
a different problem than from creating device RPs under the proper 
compute node RP.

Anyhow my simple understanding is the following:
* a physical NIC or an OVS integration bridge always belongs to one 
single hypervisor. While a hypervisor might have more than on physical 
NIC or an OVS bridge
* the identity (e.g. hypervisor hostname) of such hypervisor is known 
at deployment time
* the neutron agent config can have a mapping between the device (NIC 
or OVS bridge) and the hypervisor identity and this mapping can be sent 
up to the neutron server via RPC
* the neutron agent already sends up the service host name where the 
agent runs to the neutron server via RPC.
* the neutron server knowing the service host and the device -> 
hypervisor identity mapping can find the compute node RP under which 
the device RP needs to be created.

@Sean: Where does my list of reasoning breaks from your perspective?



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