// 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();
    }
}

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:-}]"

Order → Inventory → Payment → (Success | Compensate)

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

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

Skill("java-microservices")