nova/doc/notification_samples/instance-lock-with-reason.json

{
    "event_type":"instance.lock",
    "payload":{
        "$ref": "common_payloads/InstanceActionPayload.json#",
        "nova_object.data":{
            "locked":true,
            "locked_reason":"global warming"
        }
    },
    "priority":"INFO",
    "publisher_id":"nova-api:fake-mini"
}