【微服务架构 - 08 - Spring Cloud】06 使用熔断器防止服务雪崩

野性酷女 2022-03-22 19:00 209阅读 0赞

## Ribbon 中使用熔断器 ##

--------------------

#### 在 `pom.xml` 中增加依赖 ####

<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    </dependency>

#### 在 Application 中增加 `@EnableHystrix` 注解 ####

package com.yuu.hello.spring.cloud.web.admin.ribbon;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.hystrix.EnableHystrix;
    
    /**
     * @Classname WebAdminRibbonApplication
     * @Date 2019/1/29 0:04
     * @Created by Yuu
     */
    @SpringBootApplication
    @EnableDiscoveryClient
    @EnableHystrix
    public class WebAdminRibbonApplication {
        public static void main(String[] args) {
            SpringApplication.run(WebAdminRibbonApplication.class, args);
        }
    }

#### 在 Service 中增加 `@HystrixCommand` 注解 ####

在 Ribbon 调用方法上增加 `@HystrixCommand`注解并指定 `fallbackMethod` 熔断方法

package com.yuu.hello.spring.cloud.web.admin.ribbon.service;
    
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.web.client.RestTemplate;
    
    /**
     * @Classname AdminService
     * @Date 2019/1/29 0:09
     * @Created by Yuu
     */
    @Service
    public class AdminService {
    
        @Autowired
        private RestTemplate restTemplate;
    
        @HystrixCommand(fallbackMethod = "hiError")
        public String sayHi(String message) {
            return restTemplate.getForObject("http://HELLO-SPRING-CLOUD-SERVICE-ADMIN/hi?message=" + message, String.class);
        }
    
        public String hiError(String message) {
            return "Hi, your message is :\"" + message + "\" but request error.";
        }
    }

#### 测试熔断器 ####

此时我们关闭服务提供者，再次请求 [http://localhost:8764/hi?message=HelloRibbon][http_localhost_8764_hi_message_HelloRibbon] 浏览器会显示：

![在这里插入图片描述][2019012914183481.png]

## Feign 中使用熔断器 ##

Feign 是自带熔断器的，但默认是关闭的。需要在配置文件中配置打开它，在配置文件增加以下代码：

feign:
      hystrix:
        enabled: true

#### 在 Service 中增加 `fallback` 指定类 ####

package com.yuu.hello.spring.cloud.web.admin.feign.service;
    
    import com.yuu.hello.spring.cloud.web.admin.feign.service.hystrix.AdminServiceHystrix;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    
    /**
     * @Classname AdminService
     * @Date 2019/1/29 13:09
     * @Created by Yuu
     */
    @FeignClient(value = "hello-spring-cloud-service-admin", fallback = AdminServiceHystrix.class)
    public interface AdminService {
    
        @RequestMapping(value = "hi", method = RequestMethod.GET)
        public String sayHi(@RequestParam(value = "message") String message);
    }

#### 创建熔断器类并实现对应的 Feign 接口 ####

package com.yuu.hello.spring.cloud.web.admin.feign.service.hystrix;
    
    import com.yuu.hello.spring.cloud.web.admin.feign.service.AdminService;
    import org.springframework.stereotype.Component;
    
    /**
     * @Classname AdminServiceHystrix
     * @Date 2019/1/29 14:09
     * @Created by Yuu
     */
    @Component
    public class AdminServiceHystrix implements AdminService {
    
        @Override
        public String sayHi(String message) {
            return "Hi, your message is :\"" + message + "\" but request error";
        }
    }

#### 测试熔断器 ####

此时我们关闭服务提供者，再次请求 [http://localhost:8765/hi?message=HelloFeign][http_localhost_8765_hi_message_HelloFeign] 浏览器会显示：

![在这里插入图片描述][20190129142119685.png]

[http_localhost_8764_hi_message_HelloRibbon]: http://localhost:8764/hi?message=HelloRibbon
[2019012914183481.png]: /images/20220322/a7dcf80e217b46bdabfadade58d241f9.png
[http_localhost_8765_hi_message_HelloFeign]: http://localhost:8765/hi?message=HelloFeign
[20190129142119685.png]: /images/20220322/49e896018bc44daea17e3352c34e63b4.png