前言

由于網(wǎng)絡(luò)原因或者自身的原因，服務(wù)并不能保證100%可用，如果單個(gè)服務(wù)出現(xiàn)問題，調(diào)用這個(gè)服務(wù)就會(huì)出現(xiàn)線程阻塞，此時(shí)若有大量的請(qǐng)求涌入，Servlet容器的線程資源會(huì)被消耗完畢，導(dǎo)致服務(wù)癱瘓。服務(wù)與服務(wù)之間的依賴性，故障會(huì)傳播，會(huì)對(duì)整個(gè)微服務(wù)系統(tǒng)造成災(zāi)難性的嚴(yán)重后果，這就是服務(wù)故障的“雪崩”效應(yīng)。

為了解決這個(gè)問題，業(yè)界提出了斷路器模型。

開始創(chuàng)建

pom.xml

Feign自帶了斷路器，而RestTemplate+Ribbon沒自帶斷路器，需額外引入依賴

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

application.yml

Feign自帶的斷路器需在配置文件中開啟

feign:
    hystrix:
        enabled: true

Feign的斷路器實(shí)現(xiàn)

Feign的斷路器實(shí)現(xiàn)是增加一個(gè)斷路器的實(shí)現(xiàn)類

IHelloService

package com.asiainfo.aigov.consumer_feign.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import com.asiainfo.aigov.consumer_feign.service.impl.HelloServiceHystrix;

@FeignClient(name="eureka-client",fallback=HelloServiceHystrix.class)
public interface IHelloService {

    @RequestMapping("/hello")
    String hello(@RequestParam("name") String name);
    
}

HelloServiceHystrix

package com.asiainfo.aigov.consumer_feign.service.impl;

import org.springframework.stereotype.Service;

import com.asiainfo.aigov.consumer_feign.service.IHelloService;

@Service
public class HelloServiceHystrix implements IHelloService {

    @Override
    public String hello(String name) {
        return "invoke hello error! name -> " + name;
    }

}

RestTemplate+Ribbon的斷路器實(shí)現(xiàn)

@HystrixCommand(fallbackMethod = "helloError")
@RequestMapping("/hello2")
public String hello2(String name) {
    return restTemplate.getForObject("http://eureka-client/hello?name="+name, String.class);
}
    
public String helloError(String name) {
    return "invoke hello error! name -> " + name;
}

RestTemplate+Ribbon開啟斷路器功能

package com.asiainfo.aigov.consumer_feign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@EnableHystrix
@EnableDiscoveryClient
@EnableFeignClients
@SpringBootApplication
public class ConsumerFeignApplication {

    public static void main(String[] args) {
        SpringApplication.run(ConsumerFeignApplication.class, args);
    }
    
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
    
}

總結(jié)

斷路器開啟后，如果服務(wù)不可用，將快速返回失敗，從而防止“雪崩”效應(yīng)。