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Customizing MQTT Events

RPS and MPS microservices can publish event messages through an MQTT Broker. The following instructions demonstrate how to add, remove, or edit the events published by the server. To learn more about subscribing to these events, see Viewing MQTT Events.

Three main components can be manipulated within the MQTT event flow:

  • Individual events throughout MPS and RPS
  • MqttProvider class
  • MQTT broker

Individual Events

Add Events

To add an event:

  1. Import MqttProvider class.
  2. Use the publishEvent method to add RPS or MPS events.

Example:

import { MqttProvider } from '../../utils/mqttProvider'

MqttProvider.publishEvent('success', ['Example'], 'Hello World', guid)
The publishEvent method parameters:

Parameter Description
message type string designating the message type
array of methods methods associated with the message
message string message to be published by the event broker
GUID device GUID (optional)

Note

Learn more about publishEvent in the MqttProvider Class.

Edit or Delete Events

A number of default events have been added to RPS and MPS, such as API calls and action events. Edit or delete any events that are unnecessary or irrelevant for your deployment.

Note

Event publishing operates independently of the microservices. It will function normally with the addition, adaptation, or deletion of any individual events.

MqttProvider Class

Connect

The MqttProvider class handles the interactions with the MQTT Broker.

To establish a connection with the broker:

  1. Open the index.ts file of RPS or MPS.
  2. Add the following:

  const mqtt: MqttProvider = new MqttProvider(config)
  mqtt.connectBroker()
The connectBroker method creates the connection between a client, stored in the class, and the mosquitto docker container, which acts as the MQTT Broker. The instance of the class, after it has been created and connected, is stored as a static object within the class. This storage enables access to the methods in the class with a simple import rather than passing the instance to MPS or RPS.

The config parameter contains the config types of MPS and RPS. MqttProvider uses the MQTT_ADDRESS environment variable to establish a connection.

Important

The MQTT_ADDRESS environment variables for MPS and RPS are left blank in the .env.template file. This corresponds to the OFF state. To turn event logging with mosquitto ON provide the address of the MQTT Broker, mqtt://mosquitto:8883, to the MPS_MQTT_ADDRESS and RPS_MQTT_ADDRESS environment variables.

Usage

The publishEvent method publishes events to the MQTT Broker where subscribers can access event data. The method accepts information about an event, organizes it, adds a timestamp, and sends it to the MQTT Broker.

Expand the setup by changing the parameters and the elements within OpenAMTEvent, the interface used to organize the message, or by adding new methods. Indicate information you'd like to receive by subscribing to Topics, which are organized in a directory-like structure. Topics enable administrators to narrow eventing to subjects of interest.

Example

message type 'success'

message: 'CarStarted'

topic: cars/ford

Subscribers of #, cars or cars/ford receive the above message while subscribers of trucks or cars/ferrari will not.

Use publish to send a message to the MQTT Broker and supply a topic as the first argument. Currently, the topic is hard-coded to a default value. Alter this value by adding a parameter, tying the topic to existing parameters, or create different publishEvent methods that correspond to different topics.

MQTT Broker

The Broker for MQTT messages runs as the Docker* container mosquitto with the image eclipse-mosquitto:latest. Make changes to the functionality of the Broker through mosquitto.conf. Most of the Broker setup has been left in its default state but more information about customizing the broker can be found here.