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

  1. apiVersion: dapr.io/v1alpha1
  2. kind: Component
  3. metadata:
  4. name: mqtt-pubsub
  5. namespace: default
  6. spec:
  7. type: pubsub.mqtt
  8. version: v1
  9. metadata:
  10. - name: url
  11. value: "tcp://[username][:password]@host.domain[:port]"
  12. - name: qos
  13. value: 1
  14. - name: retain
  15. value: "false"
  16. - name: cleanSession
  17. value: "true"
  18. - name: backOffMaxRetries
  19. value: "0"

Warning

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

Spec metadata fields

FieldRequiredDetailsExample
urlYAddress of the MQTT broker. Can be secretKeyRef to use a secret reference.
Use the tcp:// URI scheme for non-TLS communication.
Use the ssl:// URI scheme for TLS communication.
“tcp://[username][:password]@host.domain[:port]”
consumerIDNThe client ID used to connect to the MQTT broker. Defaults to the Dapr app ID.“myMqttClientApp”
qosNIndicates the Quality of Service Level (QoS) of the message. Defaults to 0.1
retainNDefines whether the message is saved by the broker as the last known good value for a specified topic. Defaults to “false”.“true”, “false”
cleanSessionNSets the clean_session flag in the connection message to the MQTT broker if “true”. Defaults to “true”.“true”, “false”
caCertRequired for using TLSCertificate Authority (CA) certificate in PEM format for verifying server TLS certificates.“——-BEGIN CERTIFICATE——-\n<base64-encoded DER>\n——-END CERTIFICATE——-“
clientCertRequired for using TLSTLS client certificate in PEM format. Must be used with clientKey.“——-BEGIN CERTIFICATE——-\n<base64-encoded DER>\n——-END CERTIFICATE——-“
clientKeyRequired for using TLSTLS client key in PEM format. Must be used with clientCert. Can be secretKeyRef to use a secret reference.“——-BEGIN RSA PRIVATE KEY——-\n<base64-encoded PKCS8>\n——-END RSA PRIVATE KEY——-“
backOffMaxRetriesNThe maximum number of retries to process the message before returning an error. Defaults to “0”, which means that no retries will be attempted. “-1” can be specified to indicate that messages should be retried indefinitely until they are successfully processed or the application is shutdown. The component will wait 5 seconds between retries.“3”

Communication using TLS

To configure communication using TLS, ensure that the MQTT broker (e.g. mosquitto) is configured to support certificates and provide the caCert, clientCert, clientKey metadata in the component configuration. For example:

  1. apiVersion: dapr.io/v1alpha1
  2. kind: Component
  3. metadata:
  4. name: mqtt-pubsub
  5. namespace: default
  6. spec:
  7. type: pubsub.mqtt
  8. version: v1
  9. metadata:
  10. - name: url
  11. value: "ssl://host.domain[:port]"
  12. - name: qos
  13. value: 1
  14. - name: retain
  15. value: "false"
  16. - name: cleanSession
  17. value: "false"
  18. - name: backoffMaxRetries
  19. value: "0"
  20. - name: caCert
  21. value: ${{ myLoadedCACert }}
  22. - name: clientCert
  23. value: ${{ myLoadedClientCert }}
  24. - name: clientKey
  25. secretKeyRef:
  26. name: myMqttClientKey
  27. key: myMqttClientKey
  28. auth:
  29. secretStore: <SECRET_STORE_NAME>

Note that while the caCert and clientCert values may not be secrets, they can be referenced from a Dapr secret store as well for convenience.

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, invoking each dapr run with a different application ID is sufficient to have them consume from the same shared topic. However, on Kubernetes, multiple instances of an application pod will share 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, which will give each instance a randomly generated consumerID value on start up. For example:

  1. apiVersion: dapr.io/v1alpha1
  2. kind: Component
  3. metadata:
  4. name: mqtt-pubsub
  5. namespace: default
  6. spec:
  7. type: pubsub.mqtt
  8. version: v1
  9. metadata:
  10. - name: consumerID
  11. value: "{uuid}"
  12. - name: url
  13. value: "tcp://admin:public@localhost:1883"
  14. - name: qos
  15. value: 1
  16. - name: retain
  17. value: "false"
  18. - name: cleanSession
  19. value: "false"
  20. - name: backoffMaxRetries
  21. value: "0"

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

You can run a MQTT broker locally using Docker:

  1. 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:

  1. apiVersion: apps/v1
  2. kind: Deployment
  3. metadata:
  4. name: mqtt-broker
  5. labels:
  6. app-name: mqtt-broker
  7. spec:
  8. replicas: 1
  9. selector:
  10. matchLabels:
  11. app-name: mqtt-broker
  12. template:
  13. metadata:
  14. labels:
  15. app-name: mqtt-broker
  16. spec:
  17. containers:
  18. - name: mqtt
  19. image: eclipse-mosquitto:1.6.9
  20. imagePullPolicy: IfNotPresent
  21. ports:
  22. - name: default
  23. containerPort: 1883
  24. protocol: TCP
  25. - name: websocket
  26. containerPort: 9001
  27. protocol: TCP
  28. ---
  29. apiVersion: v1
  30. kind: Service
  31. metadata:
  32. name: mqtt-broker
  33. labels:
  34. app-name: mqtt-broker
  35. spec:
  36. type: ClusterIP
  37. selector:
  38. app-name: mqtt-broker
  39. ports:
  40. - port: 1883
  41. targetPort: default
  42. name: default
  43. protocol: TCP
  44. - port: 9001
  45. targetPort: websocket
  46. name: websocket
  47. protocol: TCP

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

Last modified June 23, 2022: Merge pull request #2550 from ItalyPaleAle/cosmosdb-harcoded-dapr-version (cf03237)