Dapr Subscriptions Example

Overview

This project demonstrates the use of Dapr for pub/sub messaging with multiple subscribers using different ways to subscribe and different programming languages.

Prerequisites

• Docker
• Kubernetes
• Dapr
• Skaffold
• Redis
• Diagrid Conductor

Project Structure

• publisher/: Java publisher application
• declarative-subscriber/: JavaScript subscriber using declarative subscriptions
• programmatic-subscriber/: Python subscriber using programmatic subscriptions
• streaming-subscriber/: Go subscriber using streaming subscriptions
• common/: Common resources and configurations
• dapr.yaml: Dapr multi-app run configuration
• skaffold.yaml: Skaffold configuration for deployment

Building the Applications

Publisher (Java)

cd publisher
mvn clean package

Declarative Subscriber (JavaScript)

cd declarative-subscriber
npm install

Programmatic Subscriber (Python)

cd programmatic-subscriber
pip install -r requirements.txt

Streaming Subscriber (Go)

cd streaming-subscriber
go mod download
go build

Running with Kubernetes, Skaffold, and Diagrid Conductor

Install Kubernetes, Dapr 1.14 and Diagrid Conductor (optional)

Follow the steps in the quickstart guide to install Kubernetes and Conductor.

Install Redis

Install Redis using Helm:

helm repo add bitnami https://charts.bitnami.com/bitnami && helm repo update && helm install redis bitnami/redis --set cluster.enabled=false --set replica.replicaCount=0 --set fullnameOverride=dapr-dev-redis

Install Skaffold (optional)

To install Skaffold, use the following command:

brew install skaffold

Deploy the application

To deploy the applications to a Kubernetes cluster:

skaffold dev

This command will build the Docker images, deploy the applications, and watch for changes.

Running with Dapr Multi-App Run CLI

To run all applications using Dapr multi-app run:

dapr run -f dapr.yaml

Testing the Application

You can test the publisher by sending a POST request:

curl -X POST http://localhost:5001/pubsub/orders \
-H "Content-Type: application/json" \
-d @order.json

Or use the Dapr CLI to publish a message:

dapr publish --publish-app-id publisher --pubsub pubsub --topic orders --data '{"orderId": "123"}'

Or use test.rest file from your IDE.

Monitoring the App with Diagrid Conductor

1. Subscription Overview: View all subscription types (declarative, programmatic, and streaming) in one consolidated dashboard in Conductor

2. Component Metrics: Analyze detailed metrics for each subscriber application:

   • Message processing and error rates
   • Latency statistics

3. Application Networking: Examine networking metrics for each application:

   • Incoming and outgoing traffic rates
   • Network latency

4. To view received messages and application behavior: check the logs from skaffold or dapr CLI.

Local Development Workflow

1. Make changes to the application code or Dapr configurations (for Java, you must rebuild the Jar files).
2. If using skaffold dev, changes will be automatically detected and redeployed.
3. If using dapr run approach, restart the Dapr multi-app run after making changes.

Additional Resources

• Blog Post on Dapr Subscriptions