Comment 27 for bug 1177830

In my folsom deployment, commit 6740c4141ea1152529b82cbf6e5b808eaba912e7 prevents new images being downloaded from Glance. Commenting the size check fixes the behaviour. As far as I can tell, this is because it is trying to get the size of an image that doesn't yet exist on disk, so the call to disk.get_disk_size(base) fails.

Tracing it through, the calls are:

 - image('disk').cache(.....) in nova.virt.libvirt.driver.LibVirtDriver._create_image() is called to start the process
 - this calls nova.virt.libvirt.imagebackend.Image.cache() with filename=<intended filename>
 - this then calls create_image() on Qcow2, with prepare_template=create_if_missing
 - create_image() then tries to check the base disk size *before* calling prepare_template (i.e. fetching the image from Glance)

Do you need any more information to help debug this? I believe the change should simply be to call prepare_template() before the disk size checks.