Cloudera Docs

MQTT Source connector

The MQTT Source connector is a Stateless NiFi dataflow developed by Cloudera that is running in the Kafka Connect framework. Learn about the connector, its properties, and configuration.

The MQTT Source connector consumes messages from an MQTT broker and transfers them to Kafka. The Kafka topic this connector transfers messages to is determined by the value of the topics property in the configuration. This connector does not perform record processing. The messages are transferred to Kafka as they are consumed from the MQTT broker. TLS can be used to establish a secure connection between the connector and the MQTT broker. The keystore and truststore files necessary for securing the connection must be present on the cluster node that the connector runs on.

Properties and configuration

Configuration is passed to the connector in a JSON file during creation. The properties of the connector can be categorized into three groups. These are as follows:

Common connector properties
These are the properties of the Kafka Connect framework that are accepted by all connectors. For a comprehensive list of these properties, see the Apache Kafka documentation.
Stateless NiFi Source properties
These are the properties that are specific to the Stateless NiFi Source connector. All Stateless NiFi Source connectors share and accept these properties. For a comprehensive list of these properties, see the Stateless NiFi Source property reference.
Connector/dataflow-specific properties
These properties are unique to this specific connector. Or to be more precise, unique to the dataflow running within the connector. These properties use the following prefix:
parameter.[***CONNECTOR NAME***] Parameters:
For a comprehensive list of these properties, see the MQTT Source properties reference.

Notes and limitations

  • Required properties must be assigned a valid value even if they are not used in the particular configuration. If a required property is not used, either leave its default value, or completely remove the property from the configuration JSON.
  • If a property that has a default value is completely removed from the configuration JSON, the system uses the default value.
  • Properties not marked as required must be completely removed from the configuration JSON if not set.
  • If the keystore-related properties are removed and an empty truststore is provided, the connector does not use TLS for connecting to the MQTT broker. TLS is used if a truststore is provided that has a key in it.
  • When the connector is deployed in a cluster environment, the system might move it from one cluster node to another. During this process, the connector is stopped, deployed to the target node, and started there. The time between the connector stopping and starting again might be several minutes. To avoid losing the messages that arrived to the MQTT broker during this time, set the following properties:
    • Set MQTT Clean Session to false.
    • Specify the MQTT Client ID.
    • Set MQTT Quality of Service to 1 or 2.

Configuration example

In this example, the connector fetches messages from an MQTT broker and transfers them to a Kafka topic.
{
 "connector.class": "org.apache.nifi.kafka.connect.StatelessNiFiSourceConnector",
 "meta.smm.predefined.flow.name": "MQTT Source",
 "meta.smm.predefined.flow.version": "1.0.0",
 "key.converter": "org.apache.kafka.connect.storage.StringConverter",
 "value.converter": "org.apache.kafka.connect.converters.ByteArrayConverter",
 "tasks.max": "1",
 "nexus.url": "https://repository.cloudera.com/artifactory/repo",
 "extensions.directory": "/tmp/nifi-stateless-extensions",
 "working.directory": "/tmp/nifi-stateless-working",
 "topics": "[***KAFKA TOPIC NAME***]",
 "parameter.MQTT Source Parameters:MQTT Broker URI": "tcp://[***HOST***]:[***PORT***]",
 "parameter.MQTT Source Parameters:MQTT Quality of Service": "0",
 "parameter.MQTT Source Parameters:MQTT Topics": "[***MQTT TOPIC NAME***]"
}
The following list collects the properties from the configuration example that must be customized for this use case:
topics
The name of the Kafka topic that the connector sends messages to.
MQTT Broker URI
The URI of the MQTT broker. In this example, the connection is not secure. As a result, the URI starts with tcp://. The port number you typically use in a case like this is 1883. If TLS is used, the URI should start with ssl://, and typically you use port number 88883.
MQTT Topics
The comma-separated list of MQTT topics that the connector fetches messages from.