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Jian Wen <wenjianhn at gmail.com> wrote:

> Hello,
>
> If we restart OvS/ovs-agent when one or more of Neutron, MySQL and
> RabbitMQ is not available, the flow rules in OvS will be gone. If
> Neutron/MySQL/RabbitMQ doesn't become available in time, the VMs
> will lose their network connections. It's not easy for an
> operations engineer to manually restore the flow rules. An
> operations engineer working under pressure at 2 a.m. will make
> mistakes.
>
> We can backup the ports info to a local file. In case of emergency
> the ovs-agent can use it to restore the flow rules. What do you
> think of this feature?
>
> Related bugs:
>     Restarting neutron openvswitch agent causes network hiccup by throwing away all flows
>     https://bugs.launchpad.net/neutron/+bug/1383674
>
>     Restarting OVS agent drops VMs traffic when using VLAN provider bridges
>     https://bugs.launchpad.net/neutron/+bug/1514056
>
>     After restarting an ovs agent, it still drops useful flows if the neutron server is busy/down
>     https://bugs.launchpad.net/neutron/+bug/1515075
>
>     Ovs agent loses OpenFlow rules if OVS gets restarted while Neutron is disconnected from SQL
>     https://bugs.launchpad.net/neutron/+bug/1531210
>

Most of those bugs are fixed (at least for stable/liberty+). Isn’t it  
enough to avoid data plane reset when the agent fails to fetch new port  
data from its controller? Why do we need another mechanism here?

Ihar