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Create an MQTT sink connector

The MQTT sink connector copies messages from an Apache Kafka® topic to an MQTT queue.

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The connector can be used to sink messages to RabbitMQ® where RabbitMQ MQTT plugin is enabled.

Prerequisites​

To set up an MQTT sink connector, you need an Aiven for Apache Kafka service with Kafka Connect enabled or a dedicated Aiven for Apache Kafka Connect cluster.

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The connector will write to a topic defined in the "connect.mqtt.kcql" configuration, so either create the topic in your Kafka service, or enable the auto_create_topic parameter so that the topic will be created automatically.

Also collect the following information about the sink MQTT server upfront:

  • USERNAME: The MQTT username to connect

  • PASSWORD: The password for the username selected

  • HOST: The MQTT hostname

  • PORT: MQTT port (usually 1883)

  • KCQL_STATEMENT: The KCQL statement to be used in the following format:

    INSERT INTO <mqtt-topic> SELECT FIELD, ... FROM <kafka-topic>

  • APACHE_KAFKA_HOST: The hostname of the Apache Kafka service, only needed when using Avro as data format

  • SCHEMA_REGISTRY_PORT: The Apache Kafka's schema registry port, only needed when using Avro as data format

  • SCHEMA_REGISTRY_USER: The Apache Kafka's schema registry username, only needed when using Avro as data format

  • SCHEMA_REGISTRY_PASSWORD: The Apache Kafka's schema registry user password, only needed when using Avro as data format

Setup an MQTT sink connector with Aiven Console​

The following example demonstrates how to setup an Apache Kafka MQTT sink connector using the Aiven Console.

Define a Kafka Connect configuration file​

Define the connector configurations in a file (we'll refer to it with the name mqtt_sink.json) with the following content. Creating a file is not strictly necessary but allows to have all the information in one place before copy/pasting them in the Aiven Console:

{
    "name": "CONNECTOR_NAME",
    "connect.mqtt.hosts": "tcp://<HOST>:<PORT>",
    "connect.mqtt.kcql": "KCQL_STATEMENT",
    "connector.class": "com.datamountaineer.streamreactor.connect.mqtt.sink.MqttSinkConnector",
    "connect.mqtt.username": "USERNAME",
    "connect.mqtt.password": "PASSWORD",
    "key.converter": "org.apache.kafka.connect.json.JsonConverter",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter"
}

The configuration file contains the following entries:

  • name: the connector name, replace CONNECTOR_NAME with the name to give to the connector.
  • connect.mqtt.hosts, connect.mqtt.kcql, connect.mqtt.username and connect.mqtt.password: sink MQTT parameters collected in the prerequisite phase.
  • key.converter and value.converter: The data converter used for this example JSON converter is used.

See the dedicated documentation for the full list of parameters.

Create a Kafka Connect connector with the Aiven Console​

To create an Apache Kafka Connect connector:

  1. Log in to the Aiven Console and select the Aiven for Apache Kafka® or Aiven for Apache Kafka Connect® service where the connector needs to be defined.

  2. Select Connectors from the left sidebar.

  3. Select Create New Connector, it is enabled only for services with Kafka Connect enabled.

  4. Select Stream Reactor MQTT Sink Connector.

  5. In the Common tab, locate the Connector configuration text box and select on Edit.

  6. Paste the connector configuration (stored in the mqtt_sink.json file) in the form.

  7. Select Apply.

    To create the connector, access the Aiven Console and select the Aiven for Apache Kafka® or Aiven for Apache Kafka® Connect service where the connector needs to be defined, then:

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    The Aiven Console parses the configuration file and fills the relevant UI fields. You can review the UI fields across the various tabs and change them if necessary. The changes will be reflected in JSON format in the Connector configuration text box.

  8. After all the settings are correctly configured, select Create connector.

  9. Verify the connector status under the Connectors screen.

  10. Verify the presence of the data in the target Apache Kafka topic, the topic name is the one defined in the KCQL_STATEMENT.

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You can also create connectors using the Aiven CLI command.