Configure the Quality of Service for MQTT Connector

The MQTT protocol enables you to specify levels of delivery assurance for inbound or outbound messages. These levels are referred to as quality of service (QoS).

The available QoS levels to configure for MQTT Connector are:

  • AT_MOST_ONCE

    Messages are delivered at most one time ("fire and forget") and delivery is not guaranteed.

  • AT_LEAST_ONCE

    Messages are delivered correctly at least one time. The message could be delivered more than once.

  • EXACTLY_ONCE

    Messages are sent once and delivery is ensured.

The quality of service is sometimes different between message publishing and message subscribing, even if the published message and the subscription have a common topic. For example, a message published with QoS 1 or 2 might not be successfully delivered to the On New Message source, if that listener source is subscribed with QoS AT_MOST_ONCE (QoS=0).