On Sun, Mar 11, 2012 at 09:18:17AM -0500, Anthony Liguori wrote: > On 03/11/2012 08:16 AM, Yonit Halperin wrote: > >Hi, > > > >We would like to implement seamless migration for Spice, i.e., keeping the > >currently opened spice client session valid after migration. > >Today, the spice client establishes the connection to the destination before > >migration starts, and when migration completes, the client's session is > >moved to > >the destination, but all the session data is being reset. > > > >We face 2 main challenges when coming to implement seamless migration: > > > >(1) Spice client must establish the connection to the destination before the > >spice password expires. However, during migration, qemu main loop is not > >processed, and when migration completes, the password might have already > >expired. > > > >Today we solve this by the async command client_migrate_info, which is > >expected > >to be called before migration starts. The command is completed > >once spice client has connected to the destination (or a timeout). > > > >Since async monitor commands are no longer supported, we are looking for a > >new > >solution. > > We need to fix async monitor commands. Luiz sent a note our to > qemu-devel recently on this topic. > > I'm not sure we'll get there for 1.1 but if we do a 3 month release > cycle for 1.2, then that's a pretty reasonable target IMHO.
What about the second part? it's independant of the async issue. > > Regards, > > Anthony Liguori > > >The straightforward solution would be to process the main loop on the > >destination side during migration. > > > >(2) In order to restore the source-client spice session in the destination, > >we > >need to pass data from the source to the destination. > >Example for such data: in flight copy paste data, in flight usb data > >We want to pass the data from the source spice server to the destination, via > >Spice client. This introduces a possible race: after migration completes, the > >source qemu can be killed before the spice-server completes transferring the > >migration data to the client. > > > >Possible solutions: > >- Have an async migration state notifiers. The migration state will change > >after > >all the notifiers complete callbacks are called. > >- libvirt will wait for qmp event corresponding to spice completing its > >migration, and only then will kill the source qemu process. > > > >Any thoughts? > > > >Thanks, > >Yonit. > > > >
