[Spice-devel] seamless migration with spice
yhalperi at redhat.com
Sun Mar 11 06:16:00 PDT 2012
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
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
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.
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.
- 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.
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