摘要：開(kāi)發(fā)階段很有意義。源碼整合配置文件中添加來(lái)開(kāi)啟編寫類，實(shí)現(xiàn)默認(rèn)用戶遠(yuǎn)程調(diào)用被限流降級(jí)，默認(rèn)用戶應(yīng)用定義可以拿到異常信息無(wú)法拿到異常信息若初啟動(dòng)應(yīng)用，設(shè)置流控規(guī)則，結(jié)果展示如下默認(rèn)用戶源碼

Github : WIKI

Sphu （指明要保護(hù)的資源名稱）

Tracer （指明調(diào)用來(lái)源,異常統(tǒng)計(jì)接口）

ContextUtil（標(biāo)示進(jìn)入調(diào)用鏈入口）

流控規(guī)則(針對(duì)來(lái)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(gè)sentinel 保護(hù)的資源，名稱是test-sentinel-api
        Entry entry = null;
        try {

            entry = SphU.entry(resourceName);
            // ...被保護(hù)的業(yè)務(wù)邏輯處理
            if (StringUtils.isEmpty(a)) {
                // Sentinel 默認(rèn)只會(huì)統(tǒng)計(jì)BlockException & BlockException的子類，如果想統(tǒng)計(jì)其他異常信息，添加Tracer
                throw new IllegalArgumentException("A is not empty.");
            }
            return a;
            // block Exception: 如果被保護(hù)的資源被限流或者降級(jí)了，就會(huì)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(tǒng)計(jì)當(dāng)前異常發(fā)生次數(shù) / 占比
            Tracer.trace(argEx);
            return "非法參數(shù)信息";
        } finally {
            if (entry != null) {
                entry.exit();
            }
            ContextUtil.exit();
        }
    }

降級(jí)規(guī)則

@GetMapping("/test-sentinel-api")
    public String testSentinelAPI(@RequestParam(required = false) String a) {

        // 定義一個(gè)sentinel 保護(hù)的資源，名稱是test-sentinel-api
        Entry entry = null;
        try {
            entry = SphU.entry("test-sentinel-api");
            // ...被保護(hù)的業(yè)務(wù)邏輯處理
            if (StringUtils.isEmpty(a)) {
                // Sentinel 默認(rèn)只會(huì)統(tǒng)計(jì)BlockException & BlockException的子類，如果想統(tǒng)計(jì)其他異常信息，添加Tracer
                throw new IllegalArgumentException("A is not empty.");
            }
            return a;
            // block Exception: 如果被保護(hù)的資源被限流或者降級(jí)了，就會(huì)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(tǒng)計(jì)當(dāng)前異常發(fā)生次數(shù) / 占比
            Tracer.trace(argEx);
            return "非法參數(shù)信息";
        } finally {
            if (entry != null) {
                entry.exit();
            }
        }

    }

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

SentinelResource 使用該注解重構(gòu)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(hù)的業(yè)務(wù)邏輯處理
          if (StringUtils.isEmpty(a)) {
              // Sentinel 默認(rèn)只會(huì)統(tǒng)計(jì)BlockException & BlockException的子類，如果想統(tǒng)計(jì)其他異常信息，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(duì)應(yīng)《限流規(guī)則》";
      }
  
      /**
       * testSentinelResource fallback method
       * {@link SentinelResource} #fallback 在< 1.6的版本中，不能補(bǔ)貨BlockException
       */
      public String fallback(String a) {
          return "fallback 對(duì)應(yīng)《降級(jí)規(guī)則》";
      }

使用 @SentinelRestTemplate.

resttemplate.sentinel.enabled可以開(kāi)關(guān)是否啟用該注解。（開(kāi)發(fā)階段很有意義。）

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

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

@Autowired
private RestTemplate restTemplate;
...

配置文件中添加 feign.sentinel.enabled: true來(lái)開(kāi)啟

編寫fallback 類，實(shí)現(xiàn)feign client

@Component
public class UserCenterFeignClientFallback implements IUserCenterFeignClient {
    @Override
    public UserDTO findById(Long userId) {
        UserDTO userDTO = new UserDTO();
        userDTO.setWxNickname("默認(rèn)用戶");
        return userDTO;
    }
}

@Slf4j
@Component
public class UserCenterFeignClientFallbackFactory implements FallbackFactory {

    @Override
    public IUserCenterFeignClient create(Throwable cause) {
        return new IUserCenterFeignClient() {
            @Override
            public UserDTO findById(Long userId) {
                log.warn("遠(yuǎn)程調(diào)用被限流/降級(jí)，{}", cause);
                UserDTO userDTO = new UserDTO();
                userDTO.setWxNickname("默認(rèn)用戶");
                return userDTO;
            }
        };
    }
}

應(yīng)用fallback class

   /**
    * IUserCenterFeignClient for 定義 user-center feign client
    * fallbackFactory 可以拿到異常信息
    * fallback 無(wú)法拿到異常信息
    *
    * @author Isaac.Zhang | 若初
    * @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);
   }
   
   

啟動(dòng)應(yīng)用，設(shè)置流控規(guī)則，結(jié)果展示如下

   {
       id: 1,
       ...
       wxNickName: "默認(rèn)用戶"
   }

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