https://github.com/openstack/nova/blob/master/nova/compute/api.py#L3290 we will reserve a device ,this is a 'call' ,not a 'cast'
then call https://github.com/openstack/nova/blob/master/nova/compute/manager.py#L1493
and then here will raise Exception https://github.com/openstack/nova/blob/master/nova/compute/utils.py#L190
https:/ /github. com/openstack/ nova/blob/ master/ nova/compute/ api.py# L3290
we will reserve a device ,this is a 'call' ,not a 'cast'
then call /github. com/openstack/ nova/blob/ master/ nova/compute/ manager. py#L1493
https:/
and then here will raise Exception /github. com/openstack/ nova/blob/ master/ nova/compute/ utils.py# L190
https:/