[Spring-Cloud-Alibaba] Sentinel 整合RestTemplate & Feign

Sentinel API

Github : WIKI

• Sphu （指明要保護的資源名稱）
• Tracer （指明調用來源,異常統計接口）
• ContextUtil（標示進入調用鏈入口）

• 流控規則(針對來源屬性)

  @GetMapping("/test-sentinel-api")
      public String testSentinelAPI(@RequestParam(required = false) String a) {
          String resourceName = "test-sentinel-api";
          
          ContextUtil.enter(resourceName, "user-center-service");
          // 定義一個sentinel 保護的資源，名稱是test-sentinel-api
          Entry entry = null;
          try {
  
              entry = SphU.entry(resourceName);
              // ...被保護的業務邏輯處理
              if (StringUtils.isEmpty(a)) {
                  // Sentinel 默認只會統計BlockException & BlockException的子類，若是想統計其餘異常信息，添加Tracer
                  throw new IllegalArgumentException("A is not empty.");
              }
              return a;
              // block Exception: 若是被保護的資源被限流或者降級了，就會拋異常出去
          } catch (BlockException e) {
              log.error("我被限流啦！！{}", e);
              return "我被限流啦！！";
          } catch (IllegalArgumentException argEx) {
              // 統計當前異常發生次數 / 佔比
              Tracer.trace(argEx);
              return "非法參數信息";
          } finally {
              if (entry != null) {
                  entry.exit();
              }
              ContextUtil.exit();
          }
      }

• 降級規則

  @GetMapping("/test-sentinel-api")
      public String testSentinelAPI(@RequestParam(required = false) String a) {
  
          // 定義一個sentinel 保護的資源，名稱是test-sentinel-api
          Entry entry = null;
          try {
              entry = SphU.entry("test-sentinel-api");
              // ...被保護的業務邏輯處理
              if (StringUtils.isEmpty(a)) {
                  // Sentinel 默認只會統計BlockException & BlockException的子類，若是想統計其餘異常信息，添加Tracer
                  throw new IllegalArgumentException("A is not empty.");
              }
              return a;
              // block Exception: 若是被保護的資源被限流或者降級了，就會拋異常出去
          } catch (BlockException e) {
              log.error("我被限流啦！！{}", e);
              return "我被限流啦！！";
          } catch (IllegalArgumentException argEx) {
              // 統計當前異常發生次數 / 佔比
              Tracer.trace(argEx);
              return "非法參數信息";
          } finally {
              if (entry != null) {
                  entry.exit();
              }
          }
  
      }

Sentinel Annotation

源碼：com.alibaba.csp.sentinel.annotation.aspectj.SentinelResourceAspect & com.alibaba.csp.sentinel.annotation.aspectj.AbstractSentinelAspectSupport

• SentinelResource 使用該註解重構上述方法

@GetMapping("/test-sentinel-resource")
      @SentinelResource(value = "test-sentinel-api", blockHandler = "blockException", fallback = "fallback")
      public String testSentinelResource(@RequestParam(required = false) String a) {
          // ...被保護的業務邏輯處理
          if (StringUtils.isEmpty(a)) {
              // Sentinel 默認只會統計BlockException & BlockException的子類，若是想統計其餘異常信息，添加Tracer
              throw new IllegalArgumentException("A is not empty.");
          }
          return a;
      }
  
      /**
       * testSentinelResource BlockException method
       */
      public String blockException(String a, BlockException e) {
          log.error("限流了,{}", e);
          return "blockHandler 對應《限流規則》";
      }
  
      /**
       * testSentinelResource fallback method
       * {@link SentinelResource} #fallback 在< 1.6的版本中，不能補貨BlockException
       */
      public String fallback(String a) {
          return "fallback 對應《降級規則》";
      }

RestTemplate 整合Sentinel

使用 @SentinelRestTemplate.

resttemplate.sentinel.enabled能夠開關是否啓用該註解。（開發階段頗有意義。）

源碼：com.springframework.cloud.alibaba.sentinel.custom.SentinelBeanPostProcessor

@Bean
@LoadBalanced
@SentinelRestTemplate
public RestTemplate restTemplate() {
    return new RestTemplate();
}

@Autowired
private RestTemplate restTemplate;
...

Feign整合 Sentinel

配置文件中添加 feign.sentinel.enabled: true來開啓

1. 編寫fallback 類，實現feign client

   @Component
   public class UserCenterFeignClientFallback implements IUserCenterFeignClient {
       @Override
       public UserDTO findById(Long userId) {
           UserDTO userDTO = new UserDTO();
           userDTO.setWxNickname("默認用戶");
           return userDTO;
       }
   }
   
   @Slf4j
   @Component
   public class UserCenterFeignClientFallbackFactory implements FallbackFactory<IUserCenterFeignClient> {
   
       @Override
       public IUserCenterFeignClient create(Throwable cause) {
           return new IUserCenterFeignClient() {
               @Override
               public UserDTO findById(Long userId) {
                   log.warn("遠程調用被限流/降級，{}", cause);
                   UserDTO userDTO = new UserDTO();
                   userDTO.setWxNickname("默認用戶");
                   return userDTO;
               }
           };
       }
   }

2. 應用fallback class

/**
    * IUserCenterFeignClient for 定義 user-center feign client
    * fallbackFactory 能夠拿到異常信息
    * fallback 沒法拿到異常信息
    *
    * @author <a href="mailto:magicianisaac@gmail.com">Isaac.Zhang | 若初</a>
    * @since 2019/7/15
    */
   @FeignClient(name = "user-center",
           // fallback = UserCenterFeignClientFallback.class,
           fallbackFactory = UserCenterFeignClientFallbackFactory.class
   )
   public interface IUserCenterFeignClient {
       @GetMapping(path = "/users/{userId}")
       public UserDTO findById(@PathVariable Long userId);
   }

1. 啓動應用，設置流控規則，結果展現以下

{
       id: 1,
       ...
       wxNickName: "默認用戶"
   }

源碼：org.springframework.cloud.alibaba.sentinel.feign.SentinelFeign