MQTT

Detailed documentation on the MQTT pubsub component

Component format

To setup MQTT pubsub create a component of type pubsub.mqtt. See this guide on how to create and apply a pubsub configuration

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: mqtt-pubsub
  namespace: default
spec:
  type: pubsub.mqtt
  version: v1
  metadata:
  - name: url
    value: "tcp://[username][:password]@host.domain[:port]"
  - name: qos
    value: 1
  - name: retain
    value: "false"
  - name: cleanSession
    value: "false"

Spec metadata fields

Communication using TLS

To configure communication using TLS, ensure mosquitto broker is configured to support certificates. Pre-requisite includes certficate authority certificate, ca issued client certificate, client private key. Here is an example.

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: mqtt-pubsub
  namespace: default
spec:
  type: pubsub.mqtt
  version: v1
  metadata:
  - name: url
    value: "tcps://host.domain[:port]"
  - name: qos
    value: 1
  - name: retain
    value: "false"
  - name: cleanSession
    value: "false"
  - name: caCert
    value: ''
  - name: clientCert
    value: ''
  - name: clientKey
    value: ''

Consuming a shared topic

When consuming a shared topic, each consumer must have a unique identifier. By default, the application Id is used to uniquely identify each consumer and publisher. In self-hosted mode, running each Dapr run with a different application Id is sufficient to have them consume from the same shared topic. However on Kubernetes, a pod with multiple application instances shares the same application Id, prohibiting all instances from consuming the same topic. To overcome this, configure the component’s ConsumerID metadata with a {uuid} tag, making each instance to have a randomly generated ConsumerID value on start up. For example:

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: messagebus
  namespace: default
spec:
  type: pubsub.mqtt
  version: v1
  metadata:
    - name: consumerID
      value: "{uuid}"
    - name: url
      value: "tcp://admin:public@localhost:1883"
    - name: qos
      value: 1
    - name: retain
      value: "false"
    - name: cleanSession
      value: "false"

Warning

The above example uses secrets as plain strings. It is recommended to use a secret store for the secrets as described here.

Create a MQTT broker

• Self-Hosted
• Kubernetes

You can run a MQTT broker locally using Docker:

docker run -d -p 1883:1883 -p 9001:9001 --name mqtt eclipse-mosquitto:1.6.9

You can then interact with the server using the client port: mqtt://localhost:1883

You can run a MQTT broker in kubernetes using following yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mqtt-broker
  labels:
    app-name: mqtt-broker
spec:
  replicas: 1
  selector:
    matchLabels:
      app-name: mqtt-broker
  template:
    metadata:
      labels:
        app-name: mqtt-broker
    spec:
      containers:
        - name: mqtt
          image: eclipse-mosquitto:1.6.9
          imagePullPolicy: IfNotPresent
          ports:
            - name: default
              containerPort: 1883
              protocol: TCP
            - name: websocket
              containerPort: 9001
              protocol: TCP
---
apiVersion: v1
kind: Service
metadata:
  name: mqtt-broker
  labels:
    app-name: mqtt-broker
spec:
  type: ClusterIP
  selector:
    app-name: mqtt-broker
  ports:
    - port: 1883
      targetPort: default
      name: default
      protocol: TCP
    - port: 9001
      targetPort: websocket
      name: websocket
      protocol: TCP

You can then interact with the server using the client port: tcp://mqtt-broker.default.svc.cluster.local:1883

Related links

• Basic schema for a Dapr component
• Read this guide for instructions on configuring pub/sub components
• Pub/Sub building block

Last modified March 18, 2021: Merge pull request #1321 from dapr/aacrawfi/logos (9a399d5)