nova-compute cannot be restarted with active Ironic instances

[Adam Gandelman]

Attempting to restart the nova-compute service with ACTIVE nova instance provisioned on an Ironic node causes the following exception:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/eventlet/hubs/poll.py", line 97, in wait
    readers.get(fileno, noop).cb(fileno)
  File "/usr/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    result = function(*args, **kwargs)
  File "/opt/stack/nova/nova/openstack/common/service.py", line 490, in run_service
    service.start()
  File "/opt/stack/nova/nova/service.py", line 179, in start
    self.manager.pre_start_hook()
  File "/opt/stack/nova/nova/compute/manager.py", line 1074, in pre_start_hook
    self.update_available_resource(nova.context.get_admin_context())
  File "/opt/stack/nova/nova/compute/manager.py", line 5457, in update_available_resource
    rt = self._get_resource_tracker(nodename)
  File "/opt/stack/nova/nova/compute/manager.py", line 609, in _get_resource_tracker
    "compute host.") % nodename)
NovaException: 5c68cb65-0c85-4fc2-8446-51a329944c97 is not a valid node managed by this compute host.

It looks like the nova driver's get_available_nodes() will return a list off all nodes /w power state (off or on), but its node_is_available() will only mark nodes available if:

        return not node.instance_uuid and not node.maintenance \
            and node.power_state == ironic_states.POWER_OFF