Spring Microservices

Spring Microservices Skill

Master building cloud-native microservices with Spring Cloud including service discovery, centralized configuration, API gateway, and resilience patterns.

Overview

This skill covers the complete Spring Cloud ecosystem for production-grade microservices architecture.

Parameters

Topics Covered

Core (Must Know)

• Service Discovery: Eureka Server/Client, service registration
• API Gateway: Spring Cloud Gateway, routing, filters
• Configuration: Spring Cloud Config Server/Client
• Load Balancing: Spring Cloud LoadBalancer

Intermediate

• Resilience: Circuit breaker, retry, timeout, bulkhead
• Distributed Tracing: Micrometer Tracing, Zipkin
• Inter-Service Communication: RestClient, Feign

Advanced

• Event-Driven: Spring Cloud Stream, Kafka, RabbitMQ
• Service Mesh: Kubernetes integration
• Multi-Region: Cross-region deployment patterns

Code Examples

Eureka Server

@SpringBootApplication
@EnableEurekaServer
public class DiscoveryServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(DiscoveryServerApplication.class, args);
    }
}

# application.yml
server:
  port: 8761
eureka:
  client:
    register-with-eureka: false
    fetch-registry: false

Spring Cloud Gateway

@Configuration
public class GatewayConfig {

    @Bean
    public RouteLocator routes(RouteLocatorBuilder builder) {
        return builder.routes()
            .route("user-service", r -> r
                .path("/api/users/**")
                .filters(f -> f
                    .stripPrefix(1)
                    .circuitBreaker(c -> c.setName("userCB").setFallbackUri("forward:/fallback"))
                    .retry(retryConfig -> retryConfig.setRetries(3)))
                .uri("lb://USER-SERVICE"))
            .build();
    }
}

Resilience4j Circuit Breaker

@Service
public class OrderClient {

    @CircuitBreaker(name = "orderService", fallbackMethod = "fallback")
    @Retry(name = "orderService")
    public List<Order> getOrders(Long userId) {
        return restClient.get()
            .uri("/orders?userId={userId}", userId)
            .retrieve()
            .body(new ParameterizedTypeReference<>() {});
    }

    public List<Order> fallback(Long userId, Throwable t) {
        log.warn("Fallback for userId: {}", userId);
        return Collections.emptyList();
    }
}

# resilience4j configuration
resilience4j:
  circuitbreaker:
    instances:
      orderService:
        failure-rate-threshold: 50
        wait-duration-in-open-state: 30s
        sliding-window-size: 10
  retry:
    instances:
      orderService:
        max-attempts: 3
        wait-duration: 1s

Distributed Tracing

management:
  tracing:
    sampling:
      probability: 1.0
  zipkin:
    tracing:
      endpoint: http://localhost:9411/api/v2/spans

logging:
  pattern:
    level: "%5p [${spring.application.name},%X{traceId:-},%X{spanId:-}]"

Troubleshooting

Failure Modes

Debug Checklist

□ Check Eureka dashboard: http://localhost:8761
□ Verify gateway routes: /actuator/gateway/routes
□ Check circuit breaker state: /actuator/circuitbreakers
□ Test config refresh: POST /actuator/refresh

Unit Test Template

@SpringBootTest
@WireMockTest(httpPort = 8089)
class OrderClientTest {

    @Autowired
    private OrderClient orderClient;

    @Test
    void shouldReturnOrdersWhenServiceAvailable() {
        stubFor(get(urlPathEqualTo("/orders"))
            .willReturn(aResponse()
                .withStatus(200)
                .withBody("[]")));

        List<Order> orders = orderClient.getOrders(1L);
        assertThat(orders).isEmpty();
    }

    @Test
    void shouldUseFallbackWhenServiceDown() {
        stubFor(get(urlPathEqualTo("/orders"))
            .willReturn(aResponse().withStatus(503)));

        List<Order> orders = orderClient.getOrders(1L);
        assertThat(orders).isEmpty(); // fallback
    }
}

Usage

Skill("spring-microservices")

Version History