Java Microservices Skill Skill

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

| Problem | Cause | Solution | |---------|-------|----------| | Cascade failure | No circuit breaker | Add Resilience4j | | Message lost | No ack | Enable manual ack | | Inconsistent data | No compensation | Implement saga | | Service not found | Discovery delay | Tune heartbeat |

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

Agent Skills: Java Microservices Skill

Skill Files