Notification Service with Kafka, Redis, and Spring Boot

This project implements a notification service as part of a microservices architecture. It leverages Kafka for asynchronous messaging, Redis for caching templates, and Spring Boot for service orchestration. The service ensures efficient delivery of notifications, scalability, and reliability.

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Features

• Template Management: Cache notification templates in Redis to reduce database load.
• Contact Management: Consume contact data through Kafka and deliver notifications.
• Rebalancer Service: Ensures all contacts are processed, even in case of failures.
• Asynchronous Messaging: Utilizes Kafka for at-least-once delivery of messages.
• Microservices Design: Decoupled architecture with separate services for templates, contacts, and rebalancing.

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Tech Stack

• Java 17
• Spring Boot 3.0
• Apache Kafka
• Redis
• PostgreSQL
• Docker & Docker Compose

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Prerequisites

1. Java 17+
2. Docker and Docker Compose
3. Kafka CLI Tools (optional for manual operations)
4. Postman or cURL (for testing APIs)

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Setup Instructions

1. Clone the Repository

git clone https://github.com/your-repo/notification-service.git
cd notification-service

2. Set Up Environment Variables

Create a .env file in the root directory and configure the following:

SPRING_DATASOURCE_URL=jdbc:postgresql://localhost:5432/notificationdb
SPRING_DATASOURCE_USERNAME=your_db_username
SPRING_DATASOURCE_PASSWORD=your_db_password
KAFKA_BOOTSTRAP_SERVERS=localhost:9092
REDIS_HOST=localhost
REDIS_PORT=6379

3. Build and Run Services

Use Docker Compose to start the services, including Kafka, Redis, and PostgreSQL:

docker-compose up --build

4. Create Kafka Topics

Run the following commands to create required topics:

docker exec -it kafka /bin/bash

# Inside Kafka container
kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 3 --topic templates-topic
kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 3 --topic contacts-topic
kafka-topics.sh --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 3 --topic notifications-topic

5. Start the Application

Run the application locally (if needed):

./mvnw spring-boot:run

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API Endpoints

Template APIs

1. Cache Template

   • POST /templates
   • Request Body:

     {
       "id": 1,
       "name": "Welcome Template",
       "content": "Hello {{name}}, welcome to our service!"
     }

2. Fetch Template by ID

   • GET /templates/{id}

3. Delete Template

   • DELETE /templates/{id}

Contact APIs

1. Consume Contacts

   • Contacts are consumed from the Kafka contacts-topic.

2. Send Notifications

   • Notifications are processed and delivered based on the template and contact data.

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Rebalancer Service

The rebalancer ensures reliable processing of contacts by:

• Identifying unprocessed contacts in Kafka or Redis.
• Retrying delivery or marking contacts as failed for manual intervention.

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Project Structure

src/main/java/com/azimsh3r/notificationservice/
├── config/          # Kafka and Redis configuration files
├── controller/      # REST controllers for APIs
├── dto/             # Data Transfer Objects (DTOs)
├── service/         # Business logic for templates, contacts, and notifications
├── repository/      # Data access layer
└── utils/           # Utility classes for common operations

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How It Works

1. API Service:
   • Publishes templates and contacts to Kafka topics (templates-topic and contacts-topic).
2. Notification Service:
   • Consumes messages from Kafka.
   • Caches templates in Redis for fast access.
   • Processes contacts and delivers notifications.
3. Rebalancer Service:
   • Verifies all contacts were processed and reattempts delivery when needed.

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Scaling

• Kafka: Add more partitions for topics to scale horizontally.
• Redis: Use Redis clusters for distributed caching.
• Kubernetes: Deploy services in Kubernetes for auto-scaling and fault tolerance.

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Contributing

Contributions are welcome! Please follow these steps:

1. Fork the repository.
2. Create a new branch (feature/your-feature).
3. Commit your changes.
4. Push to your branch and create a pull request.

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License

This project is licensed under the MIT License. See LICENSE for more details.

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Contact

For queries or issues, reach out to:

• Author: azimsh3r
• Email: azimjon.works@gmail.com