Microservices Architecture with Spring Boot

🚀 **Overview**: Microservices architecture allows us to build scalable, flexible, and independently deployable services. Instead of a single monolithic system, microservices split the application into smaller components that can scale and evolve independently. In this blog, we'll walk through a complete microservices workflow using Spring Boot — from creating services to config management, service discovery, API gateway routing, and resilience using Resilience4j.

📌 **What Are Microservices?**

- Independently deployable smaller services - Each service handles a specific business capability - Each service has its own database - Loose coupling and high scalability - Ideal for cloud-native and distributed applications

1️⃣ **Create Individual Microservices**

This is the first foundational step. You create services such as User Service, Order Service, Product Service, Payment Service, etc. Each of these services contains its own logic and database, ensuring independence and high scalability.

2️⃣ **Setting Up Spring Cloud Config Server (Centralized Configuration)**

Managing configuration for multiple services can get complex. Spring Cloud Config Server centralizes all configurations and loads them from GitHub or a remote repository. This helps maintain environment-level configs cleanly without duplication.

1@SpringBootApplication
2@EnableConfigServer
3public class ConfigServerApplication {
4    public static void main(String[] args) {
5        SpringApplication.run(ConfigServerApplication.class, args);
6    }
7}

📍 Example of config file in GitHub:

1user-service-dev.properties
2order-service-dev.properties
3product-service-dev.properties

3️⃣ **Service Discovery with Eureka Server**

Eureka solves the biggest challenge in microservices: **How do services find each other?** Instead of hardcoding URLs, each service registers with Eureka. Other services communicate using their registered service name.

1@SpringBootApplication
2@EnableEurekaServer
3public class DiscoveryServerApplication {
4    public static void main(String[] args) {
5        SpringApplication.run(DiscoveryServerApplication.class, args);
6    }
7}

4️⃣ **API Gateway with Spring Cloud Gateway + Security**

The API Gateway acts as the entry point for all client requests. It handles routing, authentication, cross-cutting concerns, filters, and load balancing. You can secure it using **Spring Security + JWT**, and route internal requests using service names via Eureka.

1spring.cloud.gateway.routes[0].id=user-service
2spring.cloud.gateway.routes[0].uri=lb://USER-SERVICE
3spring.cloud.gateway.routes[0].predicates=Path=/users/**

5️⃣ **Resilience with Resilience4j (Circuit Breaker)**

Distributed systems must handle failures gracefully. Resilience4j protects services from cascading failures using Circuit Breakers, Retries, TimeLimiters, and Bulkheads.

1@CircuitBreaker(name = "orderService", fallbackMethod = "orderFallback")
2public OrderResponse getOrders(String userId) {
3    return restTemplate.getForObject("http://ORDER-SERVICE/orders/" + userId, OrderResponse.class);
4}

📌 **Circuit Breaker Workflow:** - Tries calling a service - If failures exceed threshold → opens the circuit - Traffic is stopped to the failing service - After waitDuration → half-open state tests the service again - If healthy → circuit closes and resumes normally

6️⃣ **Final Architecture Flow**

**Client → API Gateway → Eureka Discovery → Microservices → Config Server → Databases → Resilience Layer (Resilience4j)**

✨ **Benefits of Microservices Architecture**

- Independent deployment of each service - Easy to scale only the required service - Technology flexibility (Java, Node, Go, etc.) - Better fault isolation - Increased developer productivity - Ideal for cloud and DevOps

🎯 **Conclusion**: Microservices architecture enables us to build scalable, flexible, and resilient systems. With Spring Boot, setting up services, config server, Eureka, API gateway, and Resilience4j becomes easier and production-ready. This architecture is a solid foundation for large-scale applications and cloud-native deployments.