# If there is an instance.host the instance has been scheduled and
        # sent to a cell/compute which means it was pulled from the cell db.
        # Normal delete should be attempted.
        if not instance.host:
            try:
                if self._delete_while_booting(context, instance):
                    return
                # If instance.host was not set it's possible that the Instance
                # object here was pulled from a BuildRequest object and is not
                # fully populated. Notably it will be missing an 'id' field
                # which will prevent instance.destroy from functioning
                # properly. A lookup is attempted which will either return a
                # full Instance or None if not found. If not found then it's
                # acceptable to skip the rest of the delete processing.
                cell, instance = self._lookup_instance(context, instance.uuid)
                if cell and instance:
                    with nova_context.target_cell(context, cell):
                        instance.destroy()
                        return
                if not instance:
                    # Instance is already deleted.
                    return
            except exception.ObjectActionError:
                # NOTE(melwitt): This means the instance.host changed
                # under us indicating the instance became scheduled
                # during the destroy(). Refresh the instance from the DB and
                # continue on with the delete logic for a scheduled instance.
                # NOTE(danms): If instance.host is set, we should be able to
                # do the following lookup. If not, there's not much we can
                # do to recover.
                cell, instance = self._lookup_instance(context, instance.uuid)
                if not instance:
                    # Instance is already deleted
                    return