Subscription State

Associated with: MQTT Sparkplug™ B Groups

This status attribute indicates the state of the subscription to the MQTT Sparkplug B Group that publishes the topic to which Geo SCADA Expert has subscribed.

The possible states are:

• Disconnected—The MQTT Sparkplug B Group is not In Service (see Configure the Properties on the Group Tab). This state can occur, for example, due to the Disable Group pick action being used to put the Group item out of service.

  (If the connection to the broker has failed, the state of the MQTT Sparkplug B Group will also be Failed (see below), rather than Disconnected.)

• Starting—This state indicates that Geo SCADA Expert has sent a subscribe request to the broker, but has not yet received a response from the broker. The MQTT Sparkplug B Group should only be in this state briefly, before its state changes to either Healthy or Failed (see below).

  This state relates to subscription activity, rather than Geo SCADA Expert attempting to connect to the broker.

• Failed—This state indicates one of the following:
  • The broker has rejected a subscription request. This might happen, for example, if the topic is badly formed, or if the broker deems that Geo SCADA Expert does not have permission to subscribe to the topic.
  • The connection between Geo SCADA Expert and the broker has failed. This might be due, for example, to a network issue. Refer to the Event Journal (Events List), Alarms List, and/or MQTT driver log files for more information.
• Healthy—Geo SCADA Expert is subscribed to the topic for which the MQTT Sparkplug B Group publishes data. Geo SCADA Expert is connected to the broker to which the MQTT Sparkplug B Group publishes its data, and so is capable of retrieving that published data.
• Stopping—This state indicates that Geo SCADA Expert has sent an unsubscribe request to the broker, but has not yet received a response from the broker. This state occurs, for example, when the Disable Group pick action is used on the MQTT Sparkplug B Group. The MQTT Sparkplug B Group should only be in this state briefly, before changing to the Disconnected state (see above).

  This state relates to unsubscribing activity, rather than Geo SCADA Expert attempting to disconnect from the broker.

Also see Subscription State Alarm, and Connection State.