nova/doc/notification_samples/instance-rebuild-start.json

{
    "priority": "INFO",
    "event_type": "instance.rebuild.start",
    "publisher_id": "nova-compute:compute",
    "payload": {
        "$ref": "common_payloads/InstanceActionRebuildPayload.json#",
        "nova_object.data": {
            "task_state": "rebuilding"
        }
    }
}