nRF Cloud delivery guarantees with QoS > 0

Hi!

I use nRF Cloud Lib of NCS v3.1.1. I couldn't find detailed info on how nrf_cloud_send() works with QoS > 0.

If I set QoS > 0 and get a 0 error code returned from nrf_cloud_send(), does that mean the data was successfully delivered to the cloud? I suppose no, but want to make sure.

If the 0 code doesn't actually mean that data was delivered, I would like to know the best/simplest way to implement a guaranteed data delivery.

Thank you!

0 Øyvind 1 month ago

Hello, from nrf_cloud.h we can see nrf_cloud_send() is defined:

/**
 * @brief Send data to nRF Cloud.
 *
 * This API is used for sending data to nRF Cloud.
 *
 * @param[in] msg Pointer to a structure containing data and topic
 *                information.
 *
 * @retval 0       If successful.
 * @retval -EACCES Cloud connection is not established; wait for @ref NRF_CLOUD_EVT_READY.
 * @retval -EIO Error; failed to encode data.
 * @return A negative value indicates an error.
 */
int nrf_cloud_send(const struct nrf_cloud_tx_data *msg);

Where return value = 0 means successful.

And here we also see that it uses the following structure to send data were mqtt_qos uses the same as Zephyr MQTT (zephyr/include/zephyr/net/mqtt.h)

/** @brief Structure used to send data to nRF Cloud. */
struct nrf_cloud_tx_data {
	/** Object containing data to be published */
	struct nrf_cloud_obj *obj;
	/** Pre-encoded data that is to be published if an object is not provided */
	struct nrf_cloud_data data;

	/** Endpoint topic type published to. */
	enum nrf_cloud_topic_type topic_type;
	/** Quality of Service of the message. */
	enum mqtt_qos qos;
	/** Message ID */
	uint32_t id;
};

Have a look at the sample Cellular: nRF Cloud MQTT device message (tag 3.2.4) on how they handle this.

Kind regards,
Øyvind