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

On Aug 8, 2012, at 9:49 AM, Daniel P. Berrange wrote: > 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) > This is per-port data, tied to the specific virtual port associated with the VM itself. This data is stored in the OVS DB, and is used/could be used by an entity controlling Open vSwitch on the host. For example, stats may be kept here. >From what you indicate above, can you point me at the code which handles the migration cookie?