[Spice-devel] changing the timing of spice client linking in migration (RHBZ #725009)

[Daniel P. Berrange]

On Thu, Aug 25, 2011 at 02:13:01PM +0300, Yonit Halperin wrote:
> On 08/25/2011 01:53 PM, Gerd Hoffmann wrote:
> >I've played with a approach simliar to (2) long ago.  Actually did it by
> >registering a "live" migration handler.  Didn't work that well too.
> >spice client will stay connected to both source and target for a long
> >time, and the spice code base simply couldn't handle that very well. One
> >problem was a timeout somewhere which was *way* to short.  Second was
> >that some stuff such as new connects are blocked in that "migration"
> >state.  Doesn't hurt much if that lasts a second or two, but for a few
> >minutes it isn't acceptable.  Maybe there was more which I don't remember.
> 
> If we can't connect to the target during migration, this means the
> "not seamless" solution is problematic as well, and we may need ==>
> a libvirt change <== :
> We need to connect to the target before migration starts. We can
> either do it upon client_migrate_info, under the assumption that the
> target is already up and that it is called just before migration.
> Or otherwise, we need to introduce a new command from libvirt, just
> before migration, with the same assumptions.

Yes, the target QEMU is neccessarily up by the time client_migrate_info
is run, because we need to know the SPICE port number for the running
target QEMU. We run client_migrate_info, immediately before running
migrate monitor command.

If you're wanting to ensure the client connects to target QEMU before
migrate starts, then this implies that the libspice-server.so would
block in client_migrate_info, until it knows the client has succesfully
connected to the target ? 

Daniel
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