[libvirt] qemu_driver migrateuri handling broken?

[Gregor Schaffrath]

Hi all.

Short summary on DV's request ;)

I ran into a problem migrating kvm machines with libvirt-0.6.5:

1) At first, using the same syntax for the migrateuri as with xen (just the
IP) did not work... looking into the source code (! ;) ), I found a
different syntax for qemu.

2) using tcp://<ip>:<port> just produced an 'unknown failure' on the
receiving side:
root at loadgen137:~> virsh -c qemu:///system migrate --live kvm-testnode-vnode3 qemu+tcp://10.192.11.136/system?no_verify=1 tcp://10.192.11.136:12345
error: Unknown failure
(Note: it was working like a charm when I eliminated the migrateuri
altogether, but this was not an option in all my work environments,
since one of them doesn't feature DNS, breaking migration on the
hostname alone (and keeping /etc/hosts in sync on n machines is
something I'd like to avoid, if possible ;) ))

3) removing the case distinction and the handling of the migrateuri in
the qemudDomainMigratePrepare2 function in qemu_driver.c entirely
(if-statement, and full else-part) solved both my issues.

---

The issue seems to be current with 0.7.1 as well (at least I did receive
the same error message - I did not investigate further)

---

My 2ct: ;)

I think that a wrapper like libvirt should consequently abstract
lower level details (such as 'qemu', or 'xen') as much as possible
(that's what libvirt is for, I guess :) ). 
Since the removal of the URI handling solves both the issue _and_
eliminates a case distinction between xen and qemu (painlessly, as
far as I can see), I'd suggest perhaps considering the removal. :)

As to the sending side specification of transfer ports: I think there
should always be a possiblity to leave port selection up to libvirt, as
the sending side does not necessarily an oversight over the free ports
on the receiving side. (I feel that the reason for the different syntax
including mandatory :port part was motivated by the wish to allow users
to specify ports on the sending side)

Cheers,
	Gregor Schaffrath.