[ovs-dev] [PATCH] ovn: Avoid nb_cfg update notification flooding

[Han Zhou]

On Fri, Mar 16, 2018 at 3:36 PM, Ben Pfaff <blp at ovn.org> wrote:
>
> On Fri, Mar 16, 2018 at 02:31:49PM -0700, Han Zhou wrote:
> > nb_cfg as a mechanism to "ping" OVN control plane is very useful
> > in many ways. However, the current implementation will trigger
> > update notifications flooding in the whole control plane. Each
> > HV updates to SB the nb_cfg number and all these updates are
> > notified to all the other HVs, which is O(n^2). Although updates
> > are batched in fewers notifications than n^2, it still generates
> > significant load on SB DB and also on ovn-controllers.
> >
> > To solve this problem and make the mechanism more useful in large
> > scale producation deployment, this patch separates the per HV
> > nb_cfg data in SB from the Chassis table to a separate table, so
> > that each HV can conditionally monitor and get updates only for
> > its own record.
> >
> > Signed-off-by: Han Zhou <hzhou8 at ebay.com>
>
> By removing columns this will break upgrades.  Do you have another idea?

Can we just keep the old nb_cfg column in the schema but don't use it, just
for ovsdb upgrade to work?