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

Ben Pfaff blp at ovn.org
Fri Jul 12 20:31:57 UTC 2019


On Fri, Jul 12, 2019 at 12:36:39PM -0700, Han Zhou wrote:
> 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
> OVS
> > > > 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
> in
> > > > 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
> event
> > and it does not notify main thread. Do you think we need some more
> sophisticated?
> > If so, and if you agree, I think we can work on it after 2.12 release.
> >
> > Regards,
> > Lorenzo
> >
> > >
> > > Thanks,
> > >
> > > Ben.
> > _______________________________________________
> > dev mailing list
> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> 
> 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?

That's the kind of overloading I was concerned about too.

> 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).

Good point.  Let's consider this a to-do item then.


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