[ovs-dev] [PATCH v2 0/3] OVN: add Controller Events

Han Zhou zhouhan at gmail.com
Fri Jul 12 19:36:39 UTC 2019

On Fri, Jul 12, 2019 at 11:46 AM Lorenzo Bianconi <
lorenzo.bianconi at redhat.com> wrote:
> > On Thu, Jul 11, 2019 at 05:48:42PM +0200, Lorenzo Bianconi wrote:
> > > There are situations where arrival of certain types of traffic into
> > > does not warrant a "typical" action, such as output to a specific port
> > > or dropping. Rather, the decision about what to do needs to be left
to a
> > > CMS.
> > >
> > > The series here introduces a new table, Controller_Event, for this
> > > purpose. Traffic into OVS can raise a 'controller' event that results
> > > a Controller_Event being written to the southbound database. The
> > > intention is for a CMS to see the events and take some sort of action.
> > > When the CMS has seen the event and taken appropriate action, then it
> > > can remove the correponding row in Controller_Event table.
> >
> > The series seems OK to me.  However: do we need to do something to
> > rate-limit sending messages to ovn-controller?  It seems like a flood of
> > packets could trigger a flood of OpenFlow messages to ovn-controller,
> > which could result in poor service.
> >
> > I suspect the answer is "yes", but maybe it is "yes, but it's OK for
> > 2.12 and we can add rate-limiting in the next release".
> >
> > What do you think?
> Hi Ben,
> in pinctrl_handle_empty_lb_backends_opts() I added a limit to event_table
> size. If we overcame this limit, ovn-controller discards the received
> and it does not notify main thread. Do you think we need some more
> If so, and if you agree, I think we can work on it after 2.12 release.
> Regards,
> Lorenzo
> >
> > Thanks,
> >
> > Ben.
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Hi Lorenzo,

I am worried about the flooding, too. Thanks for adding the limit for
event_table. It is good that it won't notify the main thread and update SB
DB continuously. However, pinctrl thread would still get overloaded if
controller messages keep flooding to ovn-controller. Would it be better to
use meter action in the flow to ratelimit the messages to ovn-controller,
something like what ACL log ratelimit does?

I think it is ok for the ratelimit improvement to be in next release, since
the feature is not enabled by default (i.e. controller_event opt in NB
global is not set).


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