"I'm partial to an "agent_mode" flag which will toggle the router..."

In my previous email I mention being in favor of not overloading agent_mode, I realized I had a typo that might be confusing. I'm partial to introducing something like "agent_backend" for toggling OVS vs. namespace routers, not "agent_mode". Sorry for the typo.

-Ryan

On 1/29/19 1:25 AM, Duarte Cardoso, Igor wrote:

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?

Personally, I would like to see all routers implemented completely in the OVS data path. We can't do everything at once, so the DVR-first approach here seems reasonable to me. As to the question of config flags, agent_mode has a specific meaning. It effectively tells the agent what role it's playing (SNAT, SNAT_HA, etc.), not how to do it. dvr_bridge isn't a new mode, it's really a change to the backend implementation of the router (ie the "how"). Because of that, I'm partial to an "agent_mode" flag which will toggle the router implementation between OVS and namespace implementations.

 

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).

 

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``.

 

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.

 

-Ryan