MQTT Event Publisher

MQTT event publisher is used to send events to a MQTT broker based on the configurations you provide. You can configure it with XML, JSON, and text output mapping types.

Prerequisites

Follow the steps below before starting the output MQTT event adapter configuration.

Configure WSO2 CEP by adding relevant jars to support MQTT transport.
Start the MQTT-supported server.

Creating a MQTT event publisher

For instructions on creating a MQTT event publisher, see Publishing Events .

Configuring adapter properties

Specify the Static and Dynamic Adapter Properties, when creating a MQTT event publisher using the management console as shown below.

MQTT event publisher

After entering the above adapter properties, select the Message Format which you want to apply on the published events . Also, click Advanced to define custom output mappings based on the Message Format you selected. For more information on custom output mapping types, see Publishing Events in Various Event Formats .

You can also d efine the respective adapter properties of the event publisher based on the transport type within the <to> element of the event publisher configuration in the <PRODUCT_HOME>/repository/deployment/server/eventpublishers/ directory as follows.

<eventPublisher name="MQTTOutputEventAdapter" statistics="disable" trace="disable" xmlns="http://wso2.org/carbon/eventpublisher">
  ......................
  <to eventAdapterType="mqtt">
    <property name="topic">sensordata</property>
    <property name="username">mqtt-user</property>
    <property name="qos">1</property>
    <property name="password">mqtt-password</property>
    <property name="clientId">test-client</property>
    <property name="url">tcp://localhost:1883</property>
    <property name="cleanSession">true</property>
  </to>
</eventPublisher>

The above adapter properties are described below.

Static adapter properties

Adapter Property	Description	Configuration file property	Example
Client Id	Client identifier is used by the server to identify a client when it reconnects, It used for durable subscriptions or reliable delivery of messages is required	clientId	test-client
Broker Url	MQTT broker URL. The same URL can be used f or WSO2 MB when offset=0	url	tcp://localhost:1883
Username	Username of the broker	username	mqtt-user
Password	Password of the broker	password	mqtt-password
Clean Session	Whether to persist topic subscriptions and acknowledge positions across client sessions	cleanSession	true/false
Quality of Service	Quality of service for delivering messages between clients and servers. There are three QoS levels in MQTT are as follows. At most once (0) At least once (1) Exactly once (2)	qos	0,1,2

Dynamic adapter properties

Adapter Property	Description	Configuration file property	Example
Topic	The topic that will be used to send messages to MQTT broker.	topic	sensordata