How to Configure MQTT in Quarkus Using application.properties

June 25, 2025

Setting up MQTT in Quarkus can be straightforward when leveraging Docker for development and Kubernetes for production. This guide walks you through configuring MQTT using application.properties, ensuring a smooth transition from local development to a production environment.

1. Adding Necessary Dependencies

To begin, include the required dependencies in your pom.xml:

<dependencies>
  <!--MQTT Connector-->
  <dependency>
    <groupid>io.smallrye.reactivelt;/groupid>
    <artifactid>smallrye-reactive-messaging-mqttlt;/artifactid>
  </dependency>

  <!--Kubernetes Config Extension-->
  <dependency>
    <groupid>io.quarkuslt;/groupid>
    <artifactid>quarkus-kubernetes-configlt;/artifactid>
  </dependency>
</dependencies>

The MQTT connector facilitates communication with the MQTT broker, while the Kubernetes Config extension allows your application to read configurations from Kubernetes ConfigMaps and Secrets. quarkus.io

2. Development Environment Configuration (`application-dev.properties`)

For local development, you can run an MQTT broker using Docker. Here's how to set up Eclipse Mosquitto:

docker run -d --name mqtt-dev \
  -p 1883:1883 \
  eclipse-mosquitto

In your application-dev.properties, configure the MQTT connection:

%dev.mp.messaging.incoming.mqtt-channel.connector=smallrye-mqtt
%dev.mp.messaging.incoming.mqtt-channel.host=localhost
%dev.mp.messaging.incoming.mqtt-channel.port=1883
%dev.mp.messaging.incoming.mqtt-channel.topic=dev/topic
%dev.mp.messaging.incoming.mqtt-channel.client-id=quarkus-dev-client

This setup connects your Quarkus application to the locally running MQTT broker.

3. Production Environment Configuration (`application-prod.properties`)

In a production environment, especially when deploying to Kubernetes, it's best to externalize configurations using ConfigMaps and Secrets.

Create a ConfigMap for MQTT settings:

apiVersion: v1
kind: ConfigMap
metadata:
  name: mqtt-config
data:
  mqtt.host: mqtt-broker
  mqtt.port: "1883"
  mqtt.topic: prod/topic

Create a Secret for sensitive information:

apiVersion: v1
kind: Secret
metadata:
  name: mqtt-secret
type: Opaque
data:
  mqtt.username: cHJvZHVzZXI=  # base64 for 'produser'
  mqtt.password: cHJvZHBhc3M=  # base64 for 'prodpass'

Configure your `application-prod.properties`:

%prod.mp.messaging.incoming.mqtt-channel.connector=smallrye-mqtt
%prod.mp.messaging.incoming.mqtt-channel.host=${mqtt.host}
%prod.mp.messaging.incoming.mqtt-channel.port=${mqtt.port}
%prod.mp.messaging.incoming.mqtt-channel.topic=${mqtt.topic}
%prod.mp.messaging.incoming.mqtt-channel.username=${mqtt.username}
%prod.mp.messaging.incoming.mqtt-channel.password=${mqtt.password}
%prod.mp.messaging.incoming.mqtt-channel.client-id=quarkus-prod-client

Enable Kubernetes Config in your application:

%prod.quarkus.kubernetes-config.enabled=true
%prod.quarkus.kubernetes-config.config-maps=mqtt-config
%prod.quarkus.kubernetes-config.secrets=mqtt-secret

This configuration allows your Quarkus application to retrieve MQTT settings from Kubernetes resources.

4. Switching Between Profiles

Quarkus supports configuration profiles, enabling you to switch between different environments seamlessly.

Activate the development profile:

./mvnw quarkus:dev -Dquarkus.profile=dev

For production, set the profile accordingly:

java -Dquarkus.profile=prod -jar target/quarkus-app/quarkus-run.jar

By specifying the profile, Quarkus loads the corresponding configurations from application.properties.