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

Ribbon 中使用熔断器

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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 浏览器会显示：

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 浏览器会显示：