MQTT

Lightweight messaging protocol ideal for IoT use cases

Overview

MQTT is a lightweight, publish-subscribe, machine to machine network protocol for Message queue/Message queuing service. Joule provides the ability to subscribe to events using MQTT source consumer

Example

mqttConsumer:
  broker: tcp://127.0.0.1:1883
  topic: mydevice/leaf

  clientId: myClientId
  username: lyndon
  tenant: uk
  qos: 1

  deserializer:
    transform: com.fractalworks.streams.transport.mqtt.CustomerToStreamEventTranslator
    compressed: false
    batch: false

This basic example leverages the default setting resulting in events consumed from the mydevice/leaf topic as a Customer object. This object is then transformed in to a Joule StreamEvent object to ready for platform processing.

Attributes schema

Available configuration parameters

Attribute	Description	Data Type	Required
name	Name of source stream	String
broker	Broker server address	http://<ip-address>:port
topic	Message topic to subscribe too	Strings
clientId	A unique client identifier on the server being connected too	String
username	Username	String
password	password	String
tenant	Namespace for created topics	String
qos	Quality of service	Integer Default: 0
auto reconnect	Automatically reconnect to broker on disconnection	Boolean Default: true
clean restart	This means that if a client disconnects and reconnects within 5 minutes with clean start= false,qos>1 then session state data ( e.g subscribed topics, queued messages) are retained	Boolean Default: true
sessionExpiry interval	Maximum time that the broker will maintain the session for once the client disconnects	Long Default: 300 (seconds) 5 minutes
registration message	Message to send to broker when a Joule process registers	String
user properties	Sets the user properties	Map<String, String>
connection timeout	This value, measured in seconds, defines the maximum time interval the client will wait for the network connection to the MQTT server to be established.	Integer Default: 30 (Seconds)
keepalive interval	This value, measured in seconds, defines the maximum time interval between messages sent or received. It enables the client to detect if the server is no longer available, without having to wait for the TCP/IP timeout.	Integer Default: 30 (Seconds)
deserializer	Deserialization configuration	See Deserialization Attributes section
security	Security configuration	See Security documentation

Deserialization Attributes

This topic provides configuration parameters available object deserialization process.

Attribute	Description	Data Type	Required
transform	User provided implementation	Implementation of StreamEventParser
compressed	Uncompress payload using Snappy	Boolean Default: false
batch	Flag to inform process multiple messages have been sent in payload	Boolean Default: false

Deserializer example

deserializer:
  transform: com.fractalworks.streams.transport.mqtt.CustomerToStreamEventTranslator
  compressed: false
  batch: false

Client library

org.eclipse.paho:org.eclipse.paho.mqttv5.client:1.2.5

Additional Resources

• Official Mosquitto documentation

• Good user documentation

• MQTT X UI for testing