乐趣区

SpringCloudAlibaba-Sentinel-整合RestTemplate-Feign

Sentinel API

Github : WIKI

  • Sphu(指明要保护的资源名称)
  • Tracer(指明调用来源, 异常统计接口)
  • ContextUtil(标示进入调用链入口)
  • 流控规则 (针对来源属性)

    @GetMapping("/test-sentinel-api")
        public String testSentinelAPI(@RequestParam(required = false) String a) {
            String resourceName = "test-sentinel-api";
            
            ContextUtil.enter(resourceName, "user-center-service");
            // 定义一个 sentinel 保护的资源,名称是 test-sentinel-api
            Entry entry = null;
            try {entry = SphU.entry(resourceName);
                // ... 被保护的业务逻辑处理
                if (StringUtils.isEmpty(a)) {
                    // Sentinel 默认只会统计 BlockException & BlockException 的子类,如果想统计其他异常信息,添加 Tracer
                    throw new IllegalArgumentException("A is not empty.");
                }
                return a;
                // block Exception: 如果被保护的资源被限流或者降级了,就会抛异常出去
            } catch (BlockException e) {log.error("我被限流啦!!{}", e);
                return "我被限流啦!!";
            } catch (IllegalArgumentException argEx) {
                // 统计当前异常发生次数 / 占比
                Tracer.trace(argEx);
                return "非法参数信息";
            } finally {if (entry != null) {entry.exit();
                }
                ContextUtil.exit();}
        }
  • 降级规则

    @GetMapping("/test-sentinel-api")
        public String testSentinelAPI(@RequestParam(required = false) String a) {
    
            // 定义一个 sentinel 保护的资源,名称是 test-sentinel-api
            Entry entry = null;
            try {entry = SphU.entry("test-sentinel-api");
                // ... 被保护的业务逻辑处理
                if (StringUtils.isEmpty(a)) {
                    // Sentinel 默认只会统计 BlockException & BlockException 的子类,如果想统计其他异常信息,添加 Tracer
                    throw new IllegalArgumentException("A is not empty.");
                }
                return a;
                // block Exception: 如果被保护的资源被限流或者降级了,就会抛异常出去
            } catch (BlockException e) {log.error("我被限流啦!!{}", e);
                return "我被限流啦!!";
            } catch (IllegalArgumentException argEx) {
                // 统计当前异常发生次数 / 占比
                Tracer.trace(argEx);
                return "非法参数信息";
            } finally {if (entry != null) {entry.exit();
                }
            }
    
        }

Sentinel Annotation

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

  • SentinelResource 使用该注解重构上述方法

        @GetMapping("/test-sentinel-resource")
        @SentinelResource(value = "test-sentinel-api", blockHandler = "blockException", fallback = "fallback")
        public String testSentinelResource(@RequestParam(required = false) String a) {
            // ... 被保护的业务逻辑处理
            if (StringUtils.isEmpty(a)) {
                // Sentinel 默认只会统计 BlockException & BlockException 的子类,如果想统计其他异常信息,添加 Tracer
                throw new IllegalArgumentException("A is not empty.");
            }
            return a;
        }
    
        /**
   */
  public String blockException(String a, BlockException e) {log.error("限流了,{}", e);
      return "blockHandler 对应《限流规则》";
  }

  /**
   * testSentinelResource fallback method
   * {@link SentinelResource} #fallback 在 < 1.6 的版本中,不能补货 BlockException
   */
  public String fallback(String a) {return "fallback 对应《降级规则》";}

#### RestTemplate 整合 Sentinel

使用 `@SentinelRestTemplate`.

`resttemplate.sentinel.enabled` 可以开关是否启用该注解。(开发阶段很有意义。)源码:`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` 来开启

![image-20190718210655357](/Users/zhangpan/Library/Application Support/typora-user-images/image-20190718210655357.png)

1. 编写 fallback 类,实现 feign client

@Component
public class UserCenterFeignClientFallback implements IUserCenterFeignClient {

   @Override
   public UserDTO findById(Long userId) {UserDTO userDTO = new UserDTO();
       userDTO.setWxNickname("默认用户");
       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("远程调用被限流 / 降级,{}", cause);
               UserDTO userDTO = new UserDTO();
               userDTO.setWxNickname("默认用户");
               return userDTO;
           }
       };
   }

}


2. 应用 fallback class

/**

* IUserCenterFeignClient for 定义 user-center feign client
* fallbackFactory 可以拿到异常信息
* fallback 无法拿到异常信息
*
* @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);

}


3. 启动应用,设置流控规则,结果展示如下

{

   id: 1,
   ...
   wxNickName: "默认用户"

}


源码:`org.springframework.cloud.alibaba.sentinel.feign.SentinelFeign`
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