Use Dapr to develop distributed application workloads that talk with MQTT broker

Artikel
19/11/2024

To use the MQTT broker Dapr pluggable components, deploy both the pub/sub and state store components in your application deployment along with your Dapr application. This guide shows you how to deploy an application using the Dapr SDK and MQTT broker pluggable components.

Prerequisites

Azure IoT Operations deployed - Quickstart: Run Azure IoT Operations in GitHub Codespaces with K3s
MQTT broker Dapr Components deployed - Deploy MQTT broker Dapr Components

Creating a Dapr application

Building the application

The first step is to write an application that uses a Dapr SDK to publish/subscribe or do state management.

Dapr Publish and Subscribe quickstart
Dapr State Management quickstart

Package the application

After you finish writing the Dapr application, build the container:

Package the application into a container with the following command:

Bash
```
docker build . -t my-dapr-app
```
Push it to your Container Registry of your choice, such as:

Deploy a Dapr application

The following Deployment definition contains volumes for SAT authentication and TLS certificate chain, and utilizes Dapr sidecar injection to automatically add the pluggable components to the Pod.

The following definition components might require customization to your specific application:

Component Description

template:metadata:annotations:dapr.io/inject-pluggable-components Allows the IoT Operations pluggable components to be automatically injected into the pod

template:metadata:annotations:dapr.io/app-port Tells Dapr which port your application is listening on. If your application us not using this feature (such as a pubsub subscription), then remove this line

volumes:mqtt-client-token The System Authentication Token used for authenticating the Dapr pluggable components with the MQTT broker

volumes:aio-ca-trust-bundle The chain of trust to validate the MQTT broker TLS cert. This defaults to the test certificate deployed with Azure IoT Operations

containers:name A name given to your application container

containers:image The application container you want to deploy

Component	Description
`template:metadata:annotations:dapr.io/inject-pluggable-components`	Allows the IoT Operations pluggable components to be automatically injected into the pod
`template:metadata:annotations:dapr.io/app-port`	Tells Dapr which port your application is listening on. If your application us not using this feature (such as a pubsub subscription), then remove this line
`volumes:mqtt-client-token`	The System Authentication Token used for authenticating the Dapr pluggable components with the MQTT broker
`volumes:aio-ca-trust-bundle`	The chain of trust to validate the MQTT broker TLS cert. This defaults to the test certificate deployed with Azure IoT Operations
`containers:name`	A name given to your application container
`containers:image`	The application container you want to deploy

Awas

If your Dapr application is not listening for traffic from the Dapr sidecar, then remove the dapr.io/app-port and dapr.io/app-protocol annotations otherwise the Dapr sidecar will fail to initialize.

Save the following yaml to a file named dapr-app.yaml:

yml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: dapr-client
  namespace: azure-iot-operations
  annotations:
    aio-broker-auth/group: dapr-workload
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-dapr-app
  namespace: azure-iot-operations
spec:
  selector:
    matchLabels:
      app: my-dapr-app
  template:
    metadata:
      labels:
        app: my-dapr-app
      annotations:
        dapr.io/enabled: "true"
        dapr.io/inject-pluggable-components: "true"
        dapr.io/app-id: "my-dapr-app"
        dapr.io/app-port: "6001"
        dapr.io/app-protocol: "grpc"
    spec:
      serviceAccountName: dapr-client

      volumes:
      # SAT used to authenticate between Dapr and the MQTT broker
      - name: mqtt-client-token
        projected:
          sources:
            - serviceAccountToken:
                path: mqtt-client-token
                audience: aio-internal
                expirationSeconds: 86400

      # Certificate chain for Dapr to validate the MQTT broker
      - name: aio-ca-trust-bundle
        configMap:
          name: azure-iot-operations-aio-ca-trust-bundle

      containers:
      # Container for the Dapr application 
      - name: mq-dapr-app
        image: <YOUR_DAPR_APPLICATION>

Deploy the component by running the following command:

Bash

kubectl apply -f dapr-app.yaml
kubectl get pods -w

The pod should report three containers running after a short interval, as shown in the following example output:

Output

NAME                          READY   STATUS              RESTARTS   AGE
...
my-dapr-app                   3/3     Running             0          30s

Troubleshooting

If the application doesn't start or you see the containers in CrashLoopBackoff state, the log for the daprd container often contains useful information.

Run the following command to view the logs for the daprd component:

Bash

kubectl logs -l app=my-dapr-app -c daprd

Next steps

Now that you know how to develop a Dapr application, you can run through the tutorial to Build an event-driven app with Dapr.

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