Hystrix服务熔断

标签：服务 Hystrix hystrix number springframework 熔断 result import

Hystrix的服务熔断是一种保护机制，用于防止故障和延迟的影响扩散到整个系统。当底层依赖的服务发生连续故障或错误率过高时，Hystrix将会触发服务熔断，暂时停止向该服务发送请求，并快速失败返回一个备选响应。这样可以避免对不可靠的服务进行无谓的重试，保护系统的稳定性。

一、引入依赖

1     <dependency>
2       <groupId>org.springframework.cloud</groupId>
3       <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
4     </dependency>

pom.xml

二、启用熔断功能

与服务降级类似，在启动类上添加@EnableCircuitBreaker注解来启用Hystrix的断路器功能。

 1 import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;
 2 import org.springframework.boot.SpringApplication;
 3 import org.springframework.boot.autoconfigure.SpringBootApplication;
 4 import org.springframework.boot.web.servlet.ServletRegistrationBean;
 5 import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
 6 import org.springframework.cloud.netflix.hystrix.EnableHystrix;
 7 import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
 8 import org.springframework.cloud.openfeign.EnableFeignClients;
 9 import org.springframework.context.annotation.Bean;
10 
11 /**
12  * @Classname HystrixApplication
13  * @Created by Michael
14  * @Date 2023/7/17
15  * @Description 服务降级
16  */
17 @SpringBootApplication
18 @EnableFeignClients
19 //@EnableHystrix
20 @EnableCircuitBreaker
21 @EnableHystrixDashboard
22 public class HystrixApplication {
23   /**
24    * 启用hystrix的/actuator/hystrix.stream地址映射
25    * @return
26    */
27   @Bean
28   public ServletRegistrationBean getServlet(){
29     HystrixMetricsStreamServlet streamServlet = new HystrixMetricsStreamServlet();
30     ServletRegistrationBean registrationBean = new ServletRegistrationBean(streamServlet);
31     registrationBean.setLoadOnStartup(1);
32     registrationBean.addUrlMappings("/actuator/hystrix.stream");
33     registrationBean.setName("HystrixMetricsStreamServlet");
34 
35     return registrationBean;
36   }
37 
38   public static void main(String[] args) {
39     SpringApplication.run(HystrixApplication.class,args);
40   }
41 }

HystrixApplication.java

三、定义熔断降级逻辑

在需要进行熔断的方法上，通过@HystrixCommand注解定义熔断降级逻辑，并指定备用方法。

 1 /**
 2    * 熔断处理
 3    * @param userId
 4    * @param number
 5    * @return
 6    */
 7   @GetMapping("hystrix/break/{id}")
 8   @HystrixCommand(fallbackMethod = "getUserBreaker", commandProperties = {
 9           @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"),
10           @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "50"),
11           @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "500")
12   })
13   public HttpResponseResult getUser2(@PathVariable("id")Integer userId, @RequestParam int number) {
14     System.out.println("userId => "+userId);
15     if(number % 3 == 2){
16       System.out.println(number + " is bad parameter");
17 
18       throw new IllegalArgumentException(number+" is bad parameter");
19     }
20 
21     if(number % 3 == 0){
22       try {
23         System.out.println(number + " is bad parameter");
24         Thread.sleep(600);
25       } catch (InterruptedException e) {
26         System.out.println(e.toString());
27       }
28     }
29 
30     HttpResponseResult result = new HttpResponseResult<UserVo>();
31     UserVo userVo= userClient.getUser(userId);
32     result.setStatusCode(HttpStatus.OK.value());
33     result.setMessage(HttpStatus.OK.getReasonPhrase());
34     System.out.println(userVo);
35     result.setData(userVo);
36     return result;
37   }
38 
39   public HttpResponseResult getUserBreaker(Integer userId, @RequestParam int number) {
40     System.out.println("降级处理");
41     HttpResponseResult result = new HttpResponseResult<UserVo>();
42     result.setStatusCode(HttpStatus.INTERNAL_SERVER_ERROR.value());
43     result.setMessage(HttpStatus.INTERNAL_SERVER_ERROR.getReasonPhrase());
44     result.setData(new UserVo());
45     return result;
46   }

HystrixController.java

在上述示例中，通过@HystrixProperty注解可以覆盖全局配置，对特定方法进行独立的熔断参数设置。通过number参数控制模拟场景，number为

3n+1 返回正常请求，number为3n+2模拟请求失败，number为3n模拟请求超时（n=0,1,2,...）。

当该方法发生连续故障或错误率达到阈值时，Hystrix将会触发熔断，不再向该服务发送请求，而是立即调用备用方法fallbackMethod返回备选响应。

通过使用Hystrix的服务熔断功能，可以及时隔离不可靠的服务，并快速失败，避免对故障服务的无谓重试。这有助于保护系统的可用性和稳定性，提升用户体验。

四、测试

准备provider，提供查询数据库api，hystrix module通过feign框架请求provider的api获得数据。