[ovs-discuss] [OVN] Support non-sharable meters for acl logs

Flaviof flavio at flaviof.com
Sat Oct 24 04:12:52 UTC 2020


Hello, my OVN gurus!

I've been looking at ACLs with logging.
Using Meters is a great way to keep the ovn-controllers from getting
overwhelmed with ACL log events.
Since multiple ACL rows with logging enabled can refer to the same Meter, I
ran a little experiment
to better understand how that behaves [1].

My findings were not ideal. A 'noisy' ACL match can consume all the events
allowed by the
meter, shadowing logs for other ACL(s) that also use the same meter. The
thought of maintaining
a meter row per ACL at the NB side seems like overkill. A much better
approach would be to
leverage northd to take care of this on behalf of the ACL.

Following the same line of thought that Dumitru/Numan had when splitting
the SB port group per
datapath [2], I would like to pursue a change where a single meter on the
NB may represent
multiple meters at the SB side.

In summary, I would love to hear your opinion on this. I can't imagine a
case where ACLs
sharing the same meter would benefit from getting smothered by a noisy
neighbor. But maybe
I'm not being creative enough. ;) Adding a boolean in the ACL to explicitly
say "protect my log
events from other users of the same Meter" would allow for both cases and
that is what I'm
thinking of [3] at the moment.

What do you think?

Thanks,

-- flaviof

[1]:
https://github.com/flavio-fernandes/ovsdbapp_playground/blob/acl_meter_issue/scripts/acl_meter.sh
[2]:
https://github.com/ovn-org/ovn/commit/0db5cbf65283fb41a7d28e5d0ad2f8ac14725d73
[3]:
https://github.com/flavio-fernandes/ovn/commit/f265b01fcb7866bdc697eccc151b7dedebd0085b
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