> On Mon, Dec 20, 2021 at 11:50 AM Lorenzo Bianconi <
> [email protected]> wrote:
> >
> > On Dec 20, Han Zhou wrote:
> > > On Mon, Dec 20, 2021 at 10:32 AM Lorenzo Bianconi <
> > > [email protected]> wrote:
> > > >
> > > > > On Mon, Dec 20, 2021 at 5:53 AM Lorenzo Bianconi <
> > > > > [email protected]> wrote:
> > > > > >
> > > > > > Remove global state variable and move move inc-proc code in an
> > > isolated
> > > > > > strucuture. This is a preliminary patch to add the capability to
> run
> > > > > > multiple inc-proc engines.
> > > > > >
> > > > >
> > > > > Thanks Lorenzo! Could you tell more about the use case when multiple
> > > > > inc-proc engines are required?
> > > >
> > > > Hi Han,
> > > >
> > > > I will rely on this patch to add an incremental processing engine for
> ovn
> > > > meters since in the current codebase ovs meters are updated when an
> ovn
> > > meter
> > > > is added or deleted but when it is updated.
> > >
> > > Ok, thanks for the information. For meters, there are different types,
> ones
> > > directly specified in lflows, and ones referencing SB meter table
> records.
> > > Are you talking about the SB meter records handling? For either case, it
> > > seems that we need to handle lflow together. Are we sure it is better to
> > > have a separate engine than handling in the existing engine? What would
> be
> > > the engine nodes and dependencies for the new engine?
> >
> > I guess this patch is orthogonal to the ovn-meter case, it would be useful
> > even for northd incremental processing started by Mark Gray. What do you
> think?
> 
> Maybe, but not necessary yet. I am not sure if northd would need multiple
> inc-proc instances. In general, unless two engine instances have completely
> separate nodes, there would be repeated processing for the overlapping
> nodes when we use separate inc-proc engine instances.

Since IP is managed as a library it would be nice to run it multiple times 
without
introduce any dependency (e.g. global variable or symbols).
Moreover, I think, removing the global symbols, the code would be even easier to
maintain and/or debug.

> 
> >
> > Regarding the ovn-meter use case I am referencing to the SB meter table
> but we
> > want to just update the meter bands w/o any change to the flow using the
> meter
> > (the lflow just refers to the meter UUID, not to the bands).
> 
> Ok, if it is just to reflect SB meter table change to the desired meter
> table (so that it is installed to OVS), and has nothing to do with logical
> flows, then why do we need inc-proc engine for this purpose? Would it be
> straightforward to use a FOR_EACH_TRACKED loop to handle and update? The
> inc-proc engine is required when there are multiple input dependencies.
> 
> > If we use a single engine we would be stopped by a force recompute before
> > processing the SB meter table, losing in this case the new band info.
> 
> Sorry that I didn't understand this. If the dependency is added to the
> proper place in I-P engine, it should not lose any update processing. But
> perhaps I missed your point here. Would it be better to list the dependency
> you are thinking about and then it is easier to discuss?

I think we can defer this discussion when I will post the series (I do not think
it is related to this patch). Agree?

Regards,
Lorenzo

> 
> Thanks,
> Han
> 
> > Am I missing something?
> >
> > Regards,
> > Lorenzo
> >
> > >
> > > Thanks,
> > > Han
> > >
> > > >
> > > > Regards,
> > > > Lorenzo
> > > >
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