📨 User Registration & Email Notification Microservices with Kafka, Docker, and MySQL

📖 Overview

This project demonstrates a microservices-based architecture built using Spring Boot, where two services — User Service and Email Notification Service — communicate asynchronously using Apache Kafka.

When a user registers through the User Service, the service:

1. Saves the user data into MySQL database.
2. Publishes a message to a Kafka topic.

The Email Notification Service listens to that Kafka topic as a consumer and sends an email notification to the registered user.

Both services are containerized using Docker and integrated with:

• Kafka (via Confluent Kafka image)
• Zookeeper
• MySQL

All services communicate within a single Docker network.

---

🧱 Project Architecture

                 ┌───────────────────────────┐
                 │        User Service        │
                 │  (Spring Boot + MySQL)     │
                 └──────────────┬─────────────┘
                                │
                     Kafka Producer (topic: user_registration)
                                │
                                ▼
                 ┌───────────────────────────┐
                 │  Kafka Broker + Zookeeper │
                 └──────────────┬─────────────┘
                                │
                      Kafka Consumer (topic: user_registration)
                                │
                                ▼
                 ┌───────────────────────────┐
                 │ Email Notification Service │
                 │ (Spring Boot + Mail)       │
                 └────────────────────────────┘

---

🧩 Tech Stack

• Backend: Spring Boot (Java 17)
• Message Broker: Apache Kafka
• Database: MySQL
• Containerization: Docker, Docker Compose
• Mailing: Spring Boot Starter Mail
• ORM: Spring Data JPA, Hibernate
• Build Tool: Maven

---

📁 Project Structure

---

⚙️ Configuration Details

🗄️ MySQL Configuration (Docker)

In your docker-compose.yml:

  mysql-db:
    image: mysql:8
    container_name: mysql-db
    environment:
      MYSQL_ROOT_PASSWORD: root
      MYSQL_DATABASE: userdb
    ports:
      - "3307:3306"
    networks:
      - microservice-network
  zookeeper:
    image: confluentinc/cp-zookeeper:7.4.0
    container_name: zookeeper
    environment:
      ZOOKEEPER_CLIENT_PORT: 2181
    ports:
      - "2181:2181"
    networks:
      - microservice-network

  kafka:
    image: confluentinc/cp-kafka:7.4.0
    container_name: kafka
    depends_on:
      - zookeeper
    ports:
      - "9092:9092"
    environment:
      KAFKA_BROKER_ID: 1
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092
      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
    networks:
      - microservice-network
server.port=8081
spring.application.name=user-service

# Database Configuration
spring.datasource.url=jdbc:mysql://mysql-db:3306/userdb?useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

# Kafka Configuration
spring.kafka.bootstrap-servers=kafka:9092
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer
spring.kafka.topic.name=user_registration
# Use OpenJDK 17 base image
FROM openjdk:17-jdk-alpine

# Set working directory
WORKDIR /app

# Copy Maven jar file
COPY target/*.jar app.jar

# Expose port
EXPOSE 8080

# Run the application
ENTRYPOINT ["java", "-jar", "app.jar"]


mvn clean package -DskipTests


docker-compose build --no-cache


docker-compose up