Comment 1 for bug 755666

Requesting Gamma Freeze exemption...

Benefit: Without this, instance reboot on libvirt backed instances will not work (because it deletes the domain and recreates it - it probably shouldn't do that anyway, but we can't fix that in Cactus). Any function that involves deleting a domain is likely to be broken without it (e.g. recovery), and in addition delete domains accumulate in libvirt (visible in virsh list --all).

Risk of regression: Moderate. This is not a trivial fix, but it's not super complicated either - it is just adding one extra call to "undefine". That one call expands into lots of lines of code because it has to cope if the domain is shutoff but not deleted, so we can't just keep the naive error handling. Mitigating factors:
1) Testing against my own install using KVM, including with instances in the 'stuck' state (shut down but still defined)
2) Very careful error handling code (which we probably should have throughout the libvirt code anyway)
3) Making the new behaviour as close as possible to the old behaviour (e.g. I would like to see restart reuse the domain definition, because then I think e.g. volume attachments would persist; however that would put a much higher workload on QA)