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; } /** * testSentinelResource BlockException method */ 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
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; } }; } }
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="http://www.likecs.com/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); }
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