Java微服务韧性设计模式：熔断、限流与降级实战

// 示例：使用Resilience4j配置一个熔断器 CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom()     .failureRateThreshold(50) // 失败率达到50%时熔断     .waitDurationInOpenState(Duration.ofSeconds(60)) // 熔断打开后等待60秒     .slidingWindowType(CircuitBreakerConfig.SlidingWindowType.COUNT_BASED) // 基于请求数统计     .slidingWindowSize(100) // 统计最近100个请求     .minimumNumberOfCalls(10) // 至少10个请求后才开始计算失败率     .build();  CircuitBreakerRegistry circuitBreakerRegistry = CircuitBreakerRegistry.of(circuitBreakerConfig); CircuitBreaker circuitBreaker = circuitBreakerRegistry.circuitBreaker("myService");  // 包装你的服务调用 Supplier<String> decoratedSupplier = CircuitBreaker.decorateSupplier(circuitBreaker, () -> myService.callExternalApi());  // 执行调用 try {     String result = decoratedSupplier.get();     System.out.println("Service call successful: " + result); } catch (CallNotPermittedException e) {     // 熔断器打开，请求被拒绝     System.err.println("Circuit Breaker is OPEN, call not permitted."); } catch (Exception e) {     // 其他异常处理     System.err.println("Service call failed: " + e.getMessage()); }

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// 示例：使用Resilience4j配置一个限流器 RateLimiterConfig config = RateLimiterConfig.custom()     .limitRefreshPeriod(Duration.ofSeconds(1)) // 每秒刷新一次令牌     .limitForPeriod(10) // 每秒允许10个请求     .timeoutDuration(Duration.ofSeconds(0)) // 获取令牌的等待时间，0表示不等待     .build();  RateLimiterRegistry rateLimiterRegistry = RateLimiterRegistry.of(config); RateLimiter rateLimiter = rateLimiterRegistry.rateLimiter("myApiRateLimiter");  // 包装你的服务调用 Supplier<String> decoratedSupplier = RateLimiter.decorateSupplier(rateLimiter, () -> myService.processRequest());  for (int i = 0; i < 20; i++) {     try {         String result = decoratedSupplier.get();         System.out.println("Request " + i + " processed: " + result);     } catch (RequestNotPermitted e) {         System.err.println("Request " + i + " rejected by Rate Limiter.");     } catch (Exception e) {         System.err.println("Request " + i + " failed: " + e.getMessage());     }     // 模拟请求间隔     try {         Thread.sleep(50);     } catch (InterruptedException ex) {         Thread.currentThread().interrupt();     } }

fallbackMethod

import io.resilience4j.circuitbreaker.annotation.CircuitBreaker; import io.resilience4j.ratelimiter.annotation.RateLimiter; import org.springframework.stereotype.Service;  @Service public class ProductService {      // 模拟一个外部api调用     public String getProductDetails(String productId) {         // 模拟调用失败或超时         if (Math.random() > 0.7) { // 30%的概率失败             throw new RuntimeException("External service unavailable!");         }         return "Details for product " + productId + " from external API.";     }      // 结合熔断和降级     @CircuitBreaker(name = "productService", fallbackMethod = "getProductDetailsFallback")     public String getProductDetailsWithCircuitBreaker(String productId) {         return getProductDetails(productId);     }      // 结合限流和降级     @RateLimiter(name = "productServiceRateLimiter", fallbackMethod = "getProductDetailsFallback")     public String getProductDetailsWithRateLimiter(String productId) {         return getProductDetails(productId);     }      // 降级方法     public String getProductDetailsFallback(String productId, Throwable t) {         System.err.println("Falling back for product " + productId + " due to: " + t.getMessage());         // 返回默认值或缓存数据         return "Default details for product " + productId + " (cached or simplified).";     }      // 另一个降级方法，可以处理特定异常     public String getProductDetailsFallback(String productId, RuntimeException e) {         System.err.println("Specific fallback for RuntimeException for product " + productId + ": " + e.getMessage());         return "Simplified details for product " + productId + " due to runtime error.";     } }