[kolla] Updating libvirt container images without VM downtime

J-P Methot jp.methot at planethoster.info
Fri Jan 7 21:22:30 UTC 2022

This is interesting, because it's the exact opposite of what I'm seeing 
in my test infrastructure.

If I do sudo docker restart 5b737dc80fc5 (the libvirt container), I lose 
ssh access, web console access and the dashboard's log window becomes 
empty. When the libvirt container comes back up, if I go inside the 
container and do virsh list, the return list is empty. As far as I can 
tell, the VM is effectively shutdown. The openstack dashboard still 
reports it as up, but any attempt at operations on the VM will force the 
dashboard to update and show the VM as shut off.

As far as I can tell, restarting the docker container for libvirt did 
kill off my VM here. From what you tell me, this is not the expected 
behaviour. So, I must ask, why is it acting differently in my environment?

Additionally, someone else said that the VMs were running on the host 
with the process /usr/libexec/qemu-kvm running the VM. On my compute 
host, qemu-kvm is not present in /usr/libexec. I understand that this 
could be due to an OS difference, but I thought it would be an important 
information to add.

This is kolla 12.0 on ubuntu 20.04.3 with the openstack wallaby 
container installed.

On 1/5/22 4:30 AM, Danny Webb wrote:
> If working properly the restart of the libvirtd container is a 
> non-impacting action for running VMs.  The only containers on the 
> hypervisors that have an actual impact on the VMs in the standard 
> setups are the restart of the ovs-vswitchd / ovn-controller / ovsdb 
> containers which result in a small blip of the VM neworks that we've 
> noticed.
> ------------------------------------------------------------------------
> *From:* J-P Methot <jp.methot at planethoster.info>
> *Sent:* 04 January 2022 19:17
> *To:* openstack-discuss <openstack-discuss at lists.openstack.org>
> *Subject:* [kolla] Updating libvirt container images without VM downtime
> CAUTION: This email originates from outside THG
> Hi,
> I'm looking for validation regarding the way Kolla and containers work
> in regard to upgrading the libvirt containers. Essentially, when you
> upgrade the libvirt container to a new container image, the container
> needs to be restarted, thus creating downtime for the VMs. There is no
> way to avoid this downtime, unless you migrate the VMs to another node
> and then move them back once the container has restarted, right?
> -- 
> Jean-Philippe Méthot
> Senior Openstack system administrator
> Administrateur système Openstack sénior
> PlanetHoster inc.
> Danny Webb
> Senior Linux Systems Administrator
> The Hut Group <http://www.thehutgroup.com/>
> Tel:
> Email: Danny.Webb at thehutgroup.com <mailto:Danny.Webb at thehutgroup.com>
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Jean-Philippe Méthot
Senior Openstack system administrator
Administrateur système Openstack sénior
PlanetHoster inc.

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