MQTT Source Connector for Confluent Cloud

The fully-managed MQTT Source connector for Confluent Cloud attaches to an MQTT broker, subscribes to specified topics, and streams data from these topics into Apache Kafka®.

Note

Features

The MQTT Source connector provides the following features:

  • Topics created automatically: The connector can automatically create the Kafka topic.
  • Multiple tasks: The connector supports multiple tasks. More tasks may improve performance.
  • SSL support: Supports two-way SSL.
  • MQTT client version: The connector uses paho mqttv3 client.

For more information and examples to use with the Confluent Cloud API for Connect, see the Confluent Cloud API for Connect Usage Examples section.

Limitations

Be sure to review the following information.

At least once delivery

To support at-least-once semantics, you should run the connector with mqtt.clean.session.enabled set to false. Under this mode, the connector will assign each task a unique client ID, which will be used for a persistent connection.

The topics are distributed across tasks. Confluent recommends you do not change the topic assignments–that is, do not alter the task count, or change the topic listing once the connector is up and running. This can potentially lead to data loss as the connector will be restarted with a different topic to task assignments, and hence, a different client ID.

Others

Quick Start

Use this quick start to get up and running with the Confluent Cloud MQTT source connector. The quick start shows how to attach the connector to an MQTT broker, subscribe to the specified topics, and stream data into Apache Kafka®.

Prerequisites
  • Kafka cluster credentials. The following lists the different ways you can provide credentials.
    • Enter an existing service account resource ID.
    • Create a Confluent Cloud service account for the connector. Make sure to review the ACL entries required in the service account documentation. Some connectors have specific ACL requirements.
    • Create a Confluent Cloud API key and secret. To create a key and secret, you can use confluent api-key create or you can autogenerate the API key and secret directly in the Cloud Console when setting up the connector.

Using the Confluent Cloud Console

Step 1: Launch your Confluent Cloud cluster

To create and launch a Kafka cluster in Confluent Cloud, see Create a kafka cluster in Confluent Cloud.

Step 2: Add a connector

In the left navigation menu, click Connectors. If you already have connectors in your cluster, click + Add connector.

Step 3: Select your connector

Click the MQTT Source connector card.

MQTT Source Connector Card

Step 4: Enter the connector details

Note

  • Make sure you have all your prerequisites completed.
  • An asterisk ( * ) designates a required entry.

At the Add MQTT Source Connector screen, complete the following:

Select the topic you want to send data to from the Topics list. To create a new topic, click +Add new topic.

Step 5: Check the Kafka topic

After the connector is running, verify that messages are populating your Kafka topic.

For more information and examples to use with the Confluent Cloud API for Connect, see the Confluent Cloud API for Connect Usage Examples section.

Using the Confluent CLI

Complete the following steps to set up and run the connector using the Confluent CLI.

Note

Make sure you have all your prerequisites completed.

Step 1: List the available connectors

Enter the following command to list available connectors:

confluent connect plugin list

Step 2: List the connector configuration properties

Enter the following command to show the connector configuration properties:

confluent connect plugin describe <connector-plugin-name>

The command output shows the required and optional configuration properties.

Step 3: Create the connector configuration file

Create a JSON file that contains the connector configuration properties. The following example shows the required connector properties.

{
  "connector.class": "MqttSource",
  "name": "MqttSource_0",
  "kafka.auth.mode": "KAFKA_API_KEY",
  "kafka.api.key": "<my-kafka-api-key>",
  "kafka.api.secret": "<my-kafka-api-secret>",
  "kafka.topic" : "data_topic_0",
  "mqtt.server.uri" : "tcp://192.0.0.1:1881",
  "mqtt.topics" : "broker_topic_0",
  "tasks.max" : "1"
}

Note the following property definitions:

  • "name": Sets a name for your new connector.
  • "connector.class": Identifies the connector plugin name.

  • "kafka.auth.mode": Identifies the connector authentication mode you want to use. There are two options: SERVICE_ACCOUNT or KAFKA_API_KEY (the default). To use an API key and secret, specify the configuration properties kafka.api.key and kafka.api.secret, as shown in the example configuration (above). To use a service account, specify the Resource ID in the property kafka.service.account.id=<service-account-resource-ID>. To list the available service account resource IDs, use the following command:

    confluent iam service-account list

    For example:

    confluent iam service-account list

   Id     | Resource ID |       Name        |    Description
+---------+-------------+-------------------+-------------------
   123456 | sa-l1r23m   | sa-1              | Service account 1
   789101 | sa-l4d56p   | sa-2              | Service account 2

  • "kafka.topic": The Kafka topic name where you want data sent. If not used, the default topic name created is mqtt.

  • "mqtt.server.uri": The MQTT broker URI. Must be in the format <PROTOCOL>//:URI. If the MQTT broker does not support anonymous mode, you must add the following two additional properties:

    • "mqtt.username": "<mqtt_broker_username>"
    • "mqtt.password": "<user_password>"

    The supported protocols are TCP, SSL, WS, and WSS.

    For TLS connections, you must supply the keystore and/or truststore file contents and the file passwords creating the connector configuration JSON. The truststore and keystore files are binary files. For the mqtt.ssl.trust.store.file and the mqtt.ssl.key.store.file properties, you encode the truststore or keystore file in base64, take the encoded string, add the data:text/plain:base64 prefix, and then use the entire string as the property entry. For example:

    "mqtt.ssl.key.store.file" : "data:text/plain;base64,/u3+7QAAAAIAAAACAAAAAQAGY2xpZ...omitted...=="

In addition to adding the file contents, you must also supply the passwords using the properties mqtt.ssl.key.password, mqtt.ssl.key.store.password and mqtt.ssl.trust.store.password. These are the passwords you used while creating the jks and pkcs12 keystore and truststore. For all property values and definitions, see Configuration Properties.

  • "mqtt.topics": The broker topic (or comma-separated broker topics) to subscribe to.
  • "tasks.max": Enter the number of tasks in use by the connector. The connector supports multiple tasks. More tasks may improve performance.

Single Message Transforms: See the Single Message Transforms (SMT) documentation for details about adding SMTs. See Unsupported transformations for a list of SMTs that are not supported with this connector.

Step 4: Load the properties file and create the connector

Enter the following command to load the configuration and start the connector:

confluent connect cluster create --config-file <file-name>.json

For example:

confluent connect cluster create --config-file mqtt-source.json

Example output:

Created connector MqttSource_0 lcc-ix4dl

Step 5: Check the connector status

Enter the following command to check the connector status:

confluent connect plugin list

Example output:

ID          |    Name         | Status  |  Type
+-----------+-----------------+---------+-------+
lcc-ix4dl   | MqttSource_0    | RUNNING | source

Step 6: Check the results on the broker.

After the connector is running, verify that messages are populating your Kafka topic.

For more information and examples to use with the Confluent Cloud API for Connect, see the Confluent Cloud API for Connect Usage Examples section.

Configuration Properties

Use the following configuration properties with the fully-managed connector. For self-managed connector property definitions and other details, see the connector docs in Self-managed connectors for Confluent Platform.

How should we connect to your data?

name

Sets a name for your connector.

  • Type: string
  • Valid Values: A string at most 64 characters long
  • Importance: high

Kafka Cluster credentials

kafka.auth.mode

Kafka Authentication mode. It can be one of KAFKA_API_KEY or SERVICE_ACCOUNT. It defaults to KAFKA_API_KEY mode.

  • Type: string
  • Default: KAFKA_API_KEY
  • Valid Values: KAFKA_API_KEY, SERVICE_ACCOUNT
  • Importance: high
kafka.api.key

Kafka API Key. Required when kafka.auth.mode==KAFKA_API_KEY.

  • Type: password
  • Importance: high
kafka.service.account.id

The Service Account that will be used to generate the API keys to communicate with Kafka Cluster.

  • Type: string
  • Importance: high
kafka.api.secret

Secret associated with Kafka API key. Required when kafka.auth.mode==KAFKA_API_KEY.

  • Type: password
  • Importance: high

Which topic do you want to send data to?

kafka.topic

Identifies the topic name to write the data to.

  • Type: string
  • Importance: high

How should we connect to MQTT Broker?

mqtt.server.uri

The URI of the MQTT broker. This must be given in the format <PROTOCOL>//:URI. The supported protocols are tcp, ssl, ws, wss. Note that for a connection that uses TLS, you must provide the required key stores and trust stores.

  • Type: list
  • Importance: high
mqtt.username

Username to connect with, or blank if a username is not required. Note: username field is masked as it may contain sensitive information

  • Type: password
  • Importance: high
mqtt.password

Password to connect with, or blank if a password is not required.

  • Type: password
  • Default: [hidden]
  • Importance: high

MQTT secure connection

mqtt.ssl.key.store.file

The location of the Java KeyStore file containing the private key to use for authenticating with the server.

  • Type: password
  • Default: [hidden]
  • Importance: low
mqtt.ssl.key.store.password

Password used to open the Java KeyStore file.

  • Type: password
  • Default: [hidden]
  • Importance: medium
mqtt.ssl.key.password

Password for the client certificate contained in the Java KeyStore.

  • Type: password
  • Default: [hidden]
  • Importance: high
mqtt.ssl.trust.store.file

The location of the Java TrustStore file containing the certificates required to validate the SSL connection to the server.

  • Type: password
  • Default: [hidden]
  • Importance: medium
mqtt.ssl.trust.store.password

Password used to open the Java TrustStore file.

  • Type: password
  • Default: [hidden]
  • Importance: medium

Connection Details

mqtt.clean.session.enabled

Sets whether the client and server should remember state across restarts and reconnects. Note that for unreceived messages to be received after reconnect you should set the QOS to 1 or above.

  • Type: boolean
  • Default: false
  • Importance: medium
mqtt.connect.timeout.seconds

Sets the connection timeout value in seconds.

  • Type: int
  • Default: 30
  • Importance: medium
mqtt.keepalive.interval.seconds

This value, measured in seconds, defines the maximum time interval between messages sent or received. In the absence of a data-related message during the time period, the client sends a very small “ping” message, which the server will acknowledge.

  • Type: int
  • Default: 60
  • Importance: medium
max.retry.time.ms

The maximum time in milliseconds (ms) the connector will spend backing off and retrying failed operations (connecting to the MQTT broker and publishing records).

  • Type: int
  • Default: 30000 (30 seconds)
  • Importance: medium
mqtt.topics

The MQTT topics to subscribe to.

  • Type: list
  • Importance: high
mqtt.qos

The MQTT QOS level to subscribe to. Valid values are 0, 1 and 2.

  • Type: int
  • Default: 0
  • Importance: low
records.buffer.queue.size

The capacity of the buffer queue that stores the data before sending it to the Kafka Topic.

  • Type: int
  • Default: 50000
  • Valid Values: [10000,…,100000]
  • Importance: low
records.buffer.queue.max.batch.size

The maximum size of the batch to send to Kafka topic in a single request.

  • Type: int
  • Default: 4096
  • Valid Values: [100,…,4096]
  • Importance: low
records.buffer.queue.empty.timeout

Timeout to wait on an empty buffer queue for extracting records.

  • Type: int
  • Default: 100
  • Valid Values: [10,…,10000]
  • Importance: low
records.buffer.queue.full.timeout

Timeout to wait on a full buffer queue for inserting new records.

  • Type: int
  • Default: 60000
  • Valid Values: [30000,…,300000]
  • Importance: low

Number of tasks for this connector

tasks.max

Maximum number of tasks for the connector.

  • Type: int
  • Valid Values: [1,…]
  • Importance: high

Auto-restart policy

auto.restart.on.user.error

Enable connector to automatically restart on user-actionable errors.

  • Type: boolean
  • Default: true
  • Importance: medium

Additional Configs

header.converter

The converter class for the headers. This is used to serialize and deserialize the headers of the messages.

  • Type: string
  • Importance: low
producer.override.compression.type

The compression type for all data generated by the producer.

  • Type: string
  • Importance: low
value.converter.allow.optional.map.keys

Allow optional string map key when converting from Connect Schema to Avro Schema. Applicable for Avro Converters.

  • Type: boolean
  • Importance: low
value.converter.auto.register.schemas

Specify if the Serializer should attempt to register the Schema.

  • Type: boolean
  • Importance: low
value.converter.connect.meta.data

Allow the Connect converter to add its metadata to the output schema. Applicable for Avro Converters.

  • Type: boolean
  • Importance: low
value.converter.enhanced.avro.schema.support

Enable enhanced schema support to preserve package information and Enums. Applicable for Avro Converters.

  • Type: boolean
  • Importance: low
value.converter.enhanced.protobuf.schema.support

Enable enhanced schema support to preserve package information. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.flatten.unions

Whether to flatten unions (oneofs). Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.generate.index.for.unions

Whether to generate an index suffix for unions. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.generate.struct.for.nulls

Whether to generate a struct variable for null values. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.int.for.enums

Whether to represent enums as integers. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.latest.compatibility.strict

Verify latest subject version is backward compatible when use.latest.version is true.

  • Type: boolean
  • Importance: low
value.converter.object.additional.properties

Whether to allow additional properties for object schemas. Applicable for JSON_SR Converters.

  • Type: boolean
  • Importance: low
value.converter.optional.for.nullables

Whether nullable fields should be specified with an optional label. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.optional.for.proto2

Whether proto2 optionals are supported. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.use.latest.version

Use latest version of schema in subject for serialization when auto.register.schemas is false.

  • Type: boolean
  • Importance: low
value.converter.use.optional.for.nonrequired

Whether to set non-required properties to be optional. Applicable for JSON_SR Converters.

  • Type: boolean
  • Importance: low
value.converter.wrapper.for.nullables

Whether nullable fields should use primitive wrapper messages. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
value.converter.wrapper.for.raw.primitives

Whether a wrapper message should be interpreted as a raw primitive at root level. Applicable for Protobuf Converters.

  • Type: boolean
  • Importance: low
key.converter.key.subject.name.strategy

How to construct the subject name for key schema registration.

  • Type: string
  • Default: TopicNameStrategy
  • Importance: low
value.converter.decimal.format

Specify the JSON/JSON_SR serialization format for Connect DECIMAL logical type values with two allowed literals:

BASE64 to serialize DECIMAL logical types as base64 encoded binary data and

NUMERIC to serialize Connect DECIMAL logical type values in JSON/JSON_SR as a number representing the decimal value.

  • Type: string
  • Default: BASE64
  • Importance: low
value.converter.flatten.singleton.unions

Whether to flatten singleton unions. Applicable for Avro and JSON_SR Converters.

  • Type: boolean
  • Default: false
  • Importance: low
value.converter.reference.subject.name.strategy

Set the subject reference name strategy for value. Valid entries are DefaultReferenceSubjectNameStrategy or QualifiedReferenceSubjectNameStrategy. Note that the subject reference name strategy can be selected only for PROTOBUF format with the default strategy being DefaultReferenceSubjectNameStrategy.

  • Type: string
  • Default: DefaultReferenceSubjectNameStrategy
  • Importance: low
value.converter.value.subject.name.strategy

Determines how to construct the subject name under which the value schema is registered with Schema Registry.

  • Type: string
  • Default: TopicNameStrategy
  • Importance: low

Next Steps

For an example that shows fully-managed Confluent Cloud connectors in action with Confluent Cloud ksqlDB, see the Cloud ETL Demo. This example also shows how to use Confluent CLI to manage your resources in Confluent Cloud.

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