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 MQTT event publisher configuration.

Download MQTT client library (mqtt-client-0.4.0.jar).
Add the file to <PRODUCT_HOME>/repository/components/lib/ directory.

Creating a MQTT event publisher

For instructions on creating a MQTT event publisher, see Creating Alerts.

Configuring global properties

The following global properties can be set for the MQTT event publisher type in the <DAS_HOME>/repository/conf/input-event-adapters.xml file. These properties apply to all the publishers of the mqtt type. If a global property available by default is removed, the default value of the property is considered.

Custom properties cannot be added as global properties.

Property Key	Description	Data Type	Default Value
`minThread`	The minimum number of threads (including idle threads) that should be available in the thread pool at a given time.	Integer	`8`
`maxThread`	The maximum number of threads (including idle threads) that should be available in the thread pool at a given time.	Integer	`100`
`keepAliveTimeInMillis`	The maximum number of milliseconds that idle threads should be kept alive when the total number of threads in the pool exceeds the number of cores in the machine.	Integer	`20000`
`jobQueueSize`	The maximum number of milliseconds that idle threads should be kept alive when the total number of threads in the pool exceeds the number of cores in the machine.	Integer	`10000`
`connectionKeepAliveInterval`	The time interval in milliseconds at which a check should be carried out to identify inactive threads.	Integer	`60`

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 Output Mapping Types .

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

Related samples

For more information on mqtt event publisher type, see the following sample in WSO2 CEP Documentation.

Sample 0066 - Publishing JSON Events via MQTT Transport