[libvirt] sending openvswitch "port db" info during libvirt migration

[Daniel P. Berrange]

On Tue, Aug 07, 2012 at 03:50:20PM -0400, Laine Stump wrote:
> Someone asked on IRC the other day about sending openvswitch per-port
> data (normally stored in the switch) to the destination host during a
> migration. I suggested maybe this could be handled by encoding the
> information into the interface's <virtualport> prior to migration, and
> then writing it back out to openvswitch on the destination when the
> interface was reconnected there.
> 
> I think there's a problem with that, though - they don't want to save
> the port data on the source until the instant that the interface is
> disconnected (since it is constantly changing), but by then the domain
> XML has already long ago been formatted and sent to the destination.
> 
> So is there some other way within the confines of the current migration
> protocol that this information can be sent from migration source to
> destination?

I'd be interested to know more about just what sort of data it is that
needs to be passed around. From what you describe though, the only
way to pass that info would be to store it in the migration cookie
when the 'Perform' step completes (ie QEMU now paused, no network
I/O taking place), whereupon it will be passed into the 'Finish'
step on the dest (which can set it and then resume QEMU)


Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|