Comment 4 for bug 1910209

Hi Yi Yang,
TBH that isn't surprising.
This is like saying "I have a server here, and after I pulled the power plug no one can connect to it anymore".

The important bit for this to read into IMHO is vhost-user vs. vhost-user-client
=> https://docs.openvswitch.org/en/latest/topics/dpdk/vhost-user/#vhost-user-vs-vhost-user-client

From there you'll see: " ... if OVS dies, all VMs must be restarted." that is effectively the scenario you are in when you stop the service.

But Recent versions fully support vhostuserclient in DPDK and OVS.
Using that allows you to restart the OVS without loosing the guests.
They might see a short network outage thou (which is reasonable and ok).

Now your config already states type: dpdkvhostuserclient which means you started to do the right thing. But you haven't mentioned it at all.

While OVS is down it is ok/expected that nothing works.
But when OVS is back up, then the VMs should re-connect to the sockets and networking should get up again.

Note I'm not 100% certain if the DPDK/OVS in 18.04 already had all it needed - you might consider using https://launchpad.net/~canonical-server/+archive/ubuntu/server-backports to try if that version suddenly makes you happy. If it does consider upgrading to 20.04 for a long term setup.

If I missed some detail in your report please explain and let me know.
Kind Regards
Christian