SpringCloud使用CircuitBreaker实现熔断器的详细步骤

<!-- Spring Cloud Circuit Breaker Starter -->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-circuitbreaker-resilience4j</artifactId>
</dependency>
 
<!-- Actuator（可选，用于监控） -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

resilience4j:
  circuitbreaker:
    configs:
      default:
        failureRateThreshold: 50     # 触发熔断的失败率阈值（%）
        minimumNumberOfCalls: 5       # 计算失败率的最小调用次数
        slidingWindowType: COUNT_BASED # 滑动窗口类型（基于调用次数）
        slidingWindowSize: 10         # 滑动窗口大小
        waitDurationInOpenState: 5s   # 熔断器打开后的等待时间
        permittedNumberOfCallsInHalfOpenState: 3 # 半开状态允许的调用次数
        automaticTransitionFromOpenToHalfOpenEnabled: true # 自动切换到半开状态

import org.springframework.cloud.client.circuitbreaker.CircuitBreakerFactory;
 
@Service
public class UserService {
 
    @Autowired
    private CircuitBreakerFactory circuitBreakerFactory;
 
    public String getUserInfo(String userId) {
        return circuitBreakerFactory.create("userServiceCircuitBreaker")
            .run(
                () -> {
                    // 实际业务逻辑，如远程调用
                    return remoteService.getUser(userId);
                },
                throwable -> {
                    // 降级处理
                    return "Fallback User Info";
                }
            );
    }
}

@CircuitBreaker(name = "userService", fallbackMethod = "getUserFallback")
public User getUser(String userId) {
    // 调用远程服务
}
 
// 方法签名需与原方法一致，最后添加Throwable参数
private User getUserFallback(String userId, Throwable t) {
    return new User("fallback-user", "Service Unavailable");
}

@Bean
public CircuitBreakerConfigCustomizer defaultConfig() {
    return config -> config
        .failureRateThreshold(60)
        .waitDurationInOpenState(Duration.ofSeconds(10));
}

resilience4j:
  retry:
    configs:
      default:
        maxAttempts: 3
        waitDuration: 500ms

@Bulkhead(name = "userService", type = Type.SEMAPHORE)
@CircuitBreaker(name = "userService")
public User getUser(String userId) { ... }