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 libraries 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 global properties
The following global properties can be set for the MQTT event publisher type in the <CEP_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.
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.
| 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.