On Thu, Nov 19, 2020 at 09:59:04AM -0800, Ben Pfaff wrote:
> On Thu, Nov 19, 2020 at 11:50:57AM +0100, Dumitru Ceara wrote:
> > On 11/19/20 5:15 AM, Ben Pfaff wrote:
> > > On Tue, Nov 17, 2020 at 05:50:20PM +0100, Dumitru Ceara wrote:
> > >> It is not correct for ovn-controller to pass the current SB_Global.nb_cfg
> > >> value to ofctrl_put() if there are pending changes to conditional
> > >> monitoring clauses (local or in flight).  It might be that after the
> > >> monitor condition is acked by the SB, records that were added to the SB
> > >> before SB_Global.nb_cfg was set are now sent as updates to
> > >> ovn-controller.  These should be first installed in OVS before
> > >> ovn-controller reports that it caught up with the current
> > >> SB_Global.nb_cfg value.
> > >>
> > >> Also, ofctrl_put should not advance cur_cfg if there are flow updates in
> > >> flight.
> 
> ...
> 
> > > ovn-controller has changed (advanced?) to the point that I have trouble
> > > understanding the code now.  I'm going to assume that you understand it
> > > pretty well, but please allow me to ask a question here.  Will this
> > 
> > I'm doing my best but there are so many dependencies and side effects in
> > the code..
> 
> DDlog might actually help with that, eventually.  It should allow us to
> program in the problem domain, rather than writing a lot of code to
> manage dependencies.
> 
> > > always manage to come up to date with some version of the sb, or is
> > > there a chance that it never will report a consistent value if the sb
> > > keeps changing quickly?  I wasn't able to figure that out with a quick
> > > look.
> > > 
> > 
> > Now, back to your question:
> > 
> > TLDR: If ovn-controller has to continuously change its monitor
> > conditions I *think* there is a chance that it will never report that is
> > caught up with a specific SB seqno.  However, I tried various scenarios
> > (with quick SB updates or claiming/releasing OVS interfaces in quick
> > succession) and I didn't manage to make "ovn-nbctl --wait=hv sync" block
> > indefinitely.
> 
> That's good, empirically.
> 
> > Moreover, I think the question is if it's correct for ovn-controller to
> > report it has caught up if there are unseen SB flows that correspond to
> > its currently requested but not acked monitor condition?
> 
> I think the answer is "no", which means that the next question is, how
> do we implement it properly?  I don't have an immediate answer.  The
> database interfacing code is rather complex these days.

Oh, let me give this patch a conditional "ack".   If you are pretty
confident that it makes things better, then it has my blessing:
Acked-by: Ben Pfaff <[email protected]>
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