Java Microservices Skill

Build production microservices with Spring Cloud and distributed system patterns.

Overview

This skill covers microservices architecture with Spring Cloud including service discovery, API gateway, circuit breakers, event-driven communication, and distributed tracing.

When to Use This Skill

Use when you need to:

• Design microservices architecture
• Implement service-to-service communication
• Configure resilience patterns
• Set up event-driven messaging
• Add distributed tracing

Topics Covered

Spring Cloud Components

• Config Server (centralized config)
• Service Discovery (Eureka, Consul)
• API Gateway (Spring Cloud Gateway)
• Load Balancing (Spring Cloud LoadBalancer)

Resilience Patterns

• Circuit Breaker (Resilience4j)
• Retry with backoff
• Bulkhead isolation
• Rate limiting

Event-Driven Architecture

• Apache Kafka integration
• Spring Cloud Stream
• Saga pattern
• Event sourcing basics

Observability

• Distributed tracing (Micrometer)
• Metrics (Prometheus)
• Log correlation

Quick Reference

// Saga with Choreography
@Component
public class OrderSagaListener {

    @KafkaListener(topics = "order.created")
    public void handleOrderCreated(OrderCreatedEvent event) {
        inventoryService.reserve(event.getItems());
    }

    @KafkaListener(topics = "payment.failed")
    public void handlePaymentFailed(PaymentFailedEvent event) {
        // Compensating transaction
        inventoryService.release(event.getOrderId());
        orderService.cancel(event.getOrderId());
    }
}

// Circuit Breaker Configuration
@Configuration
public class ResilienceConfig {

    @Bean
    public Customizer<Resilience4JCircuitBreakerFactory> cbCustomizer() {
        return factory -> factory.configureDefault(id ->
            new Resilience4JConfigBuilder(id)
                .circuitBreakerConfig(CircuitBreakerConfig.custom()
                    .failureRateThreshold(50)
                    .waitDurationInOpenState(Duration.ofSeconds(30))
                    .slidingWindowSize(10)
                    .build())
                .build());
    }
}

// API Gateway Routes
@Configuration
public class GatewayConfig {

    @Bean
    public RouteLocator routes(RouteLocatorBuilder builder) {
        return builder.routes()
            .route("orders", r -> r
                .path("/api/orders/**")
                .filters(f -> f
                    .stripPrefix(1)
                    .circuitBreaker(c -> c.setName("order-cb"))
                    .retry(retry -> retry.setRetries(3)))
                .uri("lb://order-service"))
            .build();
    }
}

Observability Configuration

management:
  tracing:
    sampling:
      probability: 1.0
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus

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

Common Patterns

Saga Pattern

Order → Inventory → Payment → (Success | Compensate)

Circuit Breaker States

CLOSED → (failures exceed threshold) → OPEN
OPEN → (wait duration) → HALF_OPEN
HALF_OPEN → (success) → CLOSED
HALF_OPEN → (failure) → OPEN

Troubleshooting

Common Issues

Debug Checklist

□ Trace request (traceId)
□ Check circuit breaker state
□ Verify Kafka consumer lag
□ Review gateway routes
□ Monitor retry counts

Usage

Skill("java-microservices")

Related Skills

• java-spring-boot - Spring Cloud
• java-docker - Containerization