[ovs-dev] Question on ovsdb_idl_omit_alert()

[Han Zhou]

On Thu, Jan 2, 2020 at 11:51 AM Numan Siddique <numans at ovn.org> wrote:
>
> On Fri, Jan 3, 2020 at 1:00 AM Ben Pfaff <blp at ovn.org> wrote:
> >
> > On Fri, Jan 03, 2020 at 12:45:06AM +0530, Numan Siddique wrote:
> > > Hi Ben,
> > >
> > > ovn-controller.c has the below code here [1]
> > >
> > > ovsdb_idl_omit_alert(ovnsb_idl_loop.idl, &sbrec_chassis_col_nb_cfg);
> > >
> > > From what I understand from this comment [2], when ovn-controller
> > > updates this column, SB ovsdb-server shouldn't send the
> > > update2/update3 message back to the ovn-controller and to all the
> > > other ovn-controllers right ?
> > >
> > > But I don't see it working as expected. I can see that ovsdb-server
> > > sends the update2/update3 message to all the connected clients.
> > >
> > > Is this a bug ? Or is my understanding wrong ?
> >
> > I think that is a misunderstanding.  "Omit alert" does not suppress
> > messages from ovsdb-server.  Instead, it keeps the ovsdb IDL from
> > incrementing the sequence number that indicates that something has
> > changed in the database, that is, it keeps from alerting the IDL's
> > client that something has changed.
>
> Thanks for the reply and clearing the misunderstanding.
>
> Numan
>

Hi Numan,

I had sent a patch to improve this [0], and the last discussion was [1].

Ben, if you remember, you suggested about improving the conditional monitor
in ovsdb to avoid this problem [1]. However, after checking the conditional
monitor code I feel the change is not trivial and in fact I didn't find a
proper way to do it without sacrificing ovsdb performance. So I think the
simple change in the DB schema [0] would worth it. Please let me know if
you would like to revisit it.

[0] https://patchwork.ozlabs.org/patch/899608/
[1]
https://lists.linuxfoundation.org/pipermail/ovs-dev/2018-April/346206.html

Thanks,
Han