Comment 1 for bug 1727855

The other thing is, this code in the conductor is wrong anyway since it's using the "new" image_ref requested for the rebuild:

https://github.com/openstack/nova/blob/d36dcd52c24c32418fd358d245688c86664025d5/nova/conductor/manager.py#L830

But if we're trying to reconstruct a request_spec for the instance, we should be using the orig_image_ref parameter since that's coming off the instance:

https://github.com/openstack/nova/blob/d36dcd52c24c32418fd358d245688c86664025d5/nova/compute/api.py#L2866

Before the instance.image_ref is updated from the API request:

https://github.com/openstack/nova/blob/d36dcd52c24c32418fd358d245688c86664025d5/nova/compute/api.py#L2918

Note that if we're getting here because of evacuate, the image_ref parameter isn't even passed:

https://github.com/openstack/nova/blob/d36dcd52c24c32418fd358d245688c86664025d5/nova/compute/api.py#L3978

So maybe conductor's rebuild_instance method should be passing None to scheduler_utils.build_request_spec and if image is not provided, build_request_spec can get the image from the instance using instance.image_meta.

Anyway, as noted, rebuild doesn't even care about the RequestSpec.image field so I might be overthinking this.