[neutron] OVS OpenFlow L3 DVR / dvr_bridge agent_mode

Sean Mooney smooney at redhat.com
Tue Jan 29 12:14:38 UTC 2019

On Tue, 2019-01-29 at 08:52 +0100, Slawomir Kaplonski wrote:
> Hi,
> > Wiadomość napisana przez Duarte Cardoso, Igor <igor.duarte.cardoso at intel.com> w dniu 29.01.2019, o godz. 08:25:
> > 
> > Hi Neutron,
> >  
> > I've been internally collaborating on the ``dvr_bridge`` L3 agent mode [1][2][3] work (David Shaughnessy, Xubo
> > Zhang), which allows the L3 agent to make use of Open vSwitch / OpenFlow to implement ``distributed`` IPv4 Routers
> > thus bypassing kernel namespaces and iptables and opening the door for higher performance by keeping packets in OVS
> > for longer.
> >  
> > I want to share a few questions in order to gather feedback from you. I understand parts of these questions may have
> > been answered in the past before my involvement, but I believe it's still important to revisit and clarify them.
> > This can impact how long it's going to take to complete the work and whether it can make it to stein-3.
> >  
> > 1. Should OVS support also be added to the legacy router?
> > And if so, would it make more sense to have a new variable (not ``agent_mode``) to specify what backend to use (OVS
> > or kernel) instead of creating more combinations?
> IMHO new config option could be better. Than You can have agent_mode like it is now and new „switch” to change between
> OVS and kernel backend for it. We can of course forbid some combinations at the beginning and add support for them
> later if that would be necessary.
i would like to see it implement in the legacy router case too.
there will be little extra code required to do so and it will make testing the shared code simpler.
when this feature was first concived for icehose it was targeting repalceing the legacy router and later
extended to be an alternitve to dvr. but as suggested above a new config option sound like a good way to go.
> >  
> > 2. What is expected in terms of CI for this? Regarding testing, what should this first patch include apart from the
> > unit tests? (since the l3_agent.ini needs to be configured differently).
> I think that we should propose new neutron-tempest-plugin scenario job (based on neutron-tempest-plugin-dvr-multinode-
> scenario probably) but with configured DVR mode in this new way. That should be enough for the beginning IMO.
> Of course some unit/functional tests should be added also to Your patch :)
when this was proposed a few cycles ago the expection in testing was fullstack tests + unit and functional.
the intent being to not need another job in the gate for a different routing mod however if the neutron team are open
to adding a tempest job for this configuration then that is obviously better. from my understanding of the feautre
this can be tested entirly upstream but it may be nice to add testing with dpdk via intel nfv ci which i belive still
runs on neutron changes. it should relitivly simple to change the agent mode to dvr_bridge or whatever the new option is
for the exisiting job. i am creating a personal replacement for the nfv ci for nova that will be doing some ovs-dpdk
testing also so i can look into enabling this feature to get indirect testing depending on capasity also.
> >  
> > 3. What problems can be anticipated by having the same agent managing both kernel and OVS powered routers (depending
> > on whether they were created as ``distributed``)?
> > We are experimenting with different ways of decoupling RouterInfo (mainly as part of the L3 agent refactor patch)
> > and haven't been able to find the right balance yet. On one end we have an agent that is still coupled with kernel-
> > based RouterInfo, and on the other end we have an agent that either only accepts OVS-based RouterInfos or only
> > kernel-based RouterInfos depending on the ``agent_mode``.
> Please keep in mind that there is spec about refactor RouterInfo to make it less coupled with L3 agent’s code. It’s in
> [1]. Maybe You can work on this together :)
> >  
> > We'd also appreciate reviews on the 2 patches [4][5]. The L3 refactor one should be able to pass Zuul after a
> > recheck.
> >  
> > [1] Spec: https://blueprints.launchpad.net/neutron/+spec/openflow-based-dvr
> > [2] RFE: https://bugs.launchpad.net/neutron/+bug/1705536
> > [3] Gerrit topic: https://review.openstack.org/#/q/topic:dvr_bridge+(status:open+OR+status:merged)
> > [4] L3 agent refactor patch: https://review.openstack.org/#/c/528336/29
> > [5] dvr_bridge patch: https://review.openstack.org/#/c/472289/17
> >  
> > Thank you!
> >  
> > Best regards,
> > Igor D.C.
> [1] https://review.openstack.org/#/c/625647/
>> Slawek Kaplonski
> Senior software engineer
> Red Hat

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