Unnecessary network flapping while update floatingip without port or fixed ip changed

[Taoyunxiang]

While updating a FIP without port or fixed ip changed. For example, updating its description via neutron API, or associate same floatingip and fixed ip more than once, it will delete the old one ,than add a new one[0]. It will make network flap.

Because we don't change fip and fiexd ip , so we don't need to do update in NBDB table, and the network flap should be avoided.

[0]https://github.com/openstack/neutron/blob/master/neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/ovn_client.py#L1089

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/712641

[Maciej Jozefczyk (maciejjozefczyk)]

I know that actual implementation is wrong, but we have a use-case when we need to 'empty-update' the Floating IP to make it decentralized (when it was previously centralized because of some conditions - please check [1]).

To solve this issue I think we should verify if a 'produced' by ovn_client NAT entry is different that the one existing already in the OVN DB. If its not different - we shouldn't commit.

[1] https://bugs.launchpad.net/neutron/+bug/1860662

[Maciej Jozefczyk (maciejjozefczyk)]

I cannot reproduce this issue. I was updating several times the FIP in Neutron API that leads to this delete/create in NBDB.

In meantime I had a ping:

ping 172.24.5.196 -i 0.2
--- 172.24.5.196 ping statistics ---
77 packets transmitted, 77 received, 0% packet loss, time 15419ms
rtt min/avg/max/mdev = 0.556/0.811/2.155/0.266 ms
stack@mjozefcz-devstack-qos-2:~$

Is this network flap smaller than 200 ms?

[Taoyunxiang (taoyunxiang)]

I did not test it with traffic. It must be very short, but the delete and add action actully happened. And,we should not do meaningless push/pop to DB. What do you think?

[OpenStack Infra (hudson-openstack)]

Change abandoned by Slawek Kaplonski (<email address hidden>) on branch: master
Review: https://review.opendev.org/712641
Reason: This review is > 4 weeks without comment, and failed Zuul jobs the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.