SpringCloudAlibaba-Sentinel-整合RestTemplate-Feign

jiezi

5 年前

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();
            }
        }

    }

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`

SpringCloudAlibaba-Sentinel-整合RestTemplate-Feign

Sentinel API

Sentinel Annotation