Spring Cloud(Finchley版本)系列教程(四) 断路器(Hystrix)

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一、断路器Hystrix

hystrix是Netlifx开源的一款容错框架，防雪崩利器，具备服务降级，服务熔断，依赖隔离，监控(Hystrix Dashboard)等功能。hystrix是一个库，通过延迟容忍和容错逻辑，控制分布式服务之间的交互。它通过隔离服务间的访问点、防止级联失败和提供回退选项，保证系统的整体弹性。

二、在Ribbon中使用断路器

复制eurekaClientConsumer项目，重命名为hepServiceRibbonHystrix，修改artifactId、name、description为hepServiceRibbonHystrix，并增加hystrix依赖。

<artifactId>hepServiceRibbonHystrix</artifactId>
<name>hepServiceRibbonHystrix</name> 
<description>hepServiceRibbonHystrix</description>

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

修改EurekaClientConsumerApplication启动类为HepServiceRibbonHystrix，并在程序的启动类HepServiceRibbonHystrix加@EnableHystrix注解开启Hystrix。

package cc.huerpu.eurekaserver;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
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.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
@EnableHystrix
public class HepServiceRibbonHystrix {
    public static void main(String[] args) {
        SpringApplication.run(HepServiceRibbonHystrix.class, args);
    }
    @Bean
    public IRule ribbonRule() {
        // 负载均衡规则，改为随机
        return new RandomRule();
    }
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

修改原来ConsumerController类中的消费接口，增加@HystrixCommand注解，并指定回调方法

@RequestMapping("/consumerEurekaClient")
@HystrixCommand(fallbackMethod = "consumerEurekaClientErrorHandler")
public String consumerEurekaClient(){
    String res = restTemplate.getForObject("http://eurekaClient/getUserById",String.class);
    System.out.println(res);
    return "consumerEurekaClient:" + res;
}

public String consumerEurekaClientErrorHandler() {
    return "consumerEurekaClientErrorHandler:sorry,EurekaClient cannot handle this request,please try later!";
}

修改项目端口号为8005。

浏览器访问http://localhost:8005/consumerEurekaClient，此时http://eurekaClient/getUserById接口是停掉的，也就成功返回了consumerEurekaClientErrorHandler回调函数的字符串。

三、在OpenFeign中使用断路器

复制项目hepServiceOpenFeign，重命名为hepServiceOpenFeignHystrix，修改artifactId、name、description为hepServiceOpenFeignHystrix

<artifactId>hepServiceOpenFeignHystrix</artifactId>
<name>hepServiceOpenFeignHystrix</name>
<description>hepServiceOpenFeignHystrix</description>

<!-- 并增加web依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

修改项目名称为HepServiceOpenFeignHystrixApplication。

package cc.huerpu.eurekaserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class HepServiceOpenFeignHystrixApplication {
    public static void main(String[] args) {
        SpringApplication.run(HepServiceOpenFeignHystrixApplication.class, args);
    }
}

在UserService接口上增加fallback = OpenFeignHytrix.class，OpenFeignHytrix实现UserService接口，用于处理调用失败的回调。

package cc.huerpu.eurekaserver.feign;

import cc.huerpu.eurekaserver.config.OpenFeignConfig;
import cc.huerpu.eurekaserver.config.OpenFeignHytrix;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient(value = "eurekaClient",configuration = OpenFeignConfig.class,fallback = OpenFeignHytrix.class)
public interface UserService {
    @RequestMapping(value = "/getUserById")
    String getUserById();
}

定义一个OpenFeignHytrix，实现UserService，并让它注入到容器中。

package cc.huerpu.eurekaserver.config;

import cc.huerpu.eurekaserver.feign.UserService;
import org.springframework.stereotype.Component;

@Component
public class OpenFeignHytrix implements UserService {
    @Override
    public String getUserById(){
        return "Sorry  call getUserById interface error, OpenFeignHytrix recommend you try later " ;
    }
}

在配置文件中打开hystrix

feign:
  hystrix:
    enabled: true

修改项目端口号为8009，重启项目，调用http://localhost:8009/getUserByIdFeign，此时只启动了HepServiceOpenFeignHystrixApplication一个项目，其余项目都没运行，因此触发了Hystrix熔断

四、整合Dashboard查看监控数据

在项目hepServiceRibbonHystrix中添加hystrix-dashboar依赖 ，并确保有actuator健康检查依赖。

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

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

在启动类上增加@EnableHystrixDashboard注解。

package cc.huerpu.eurekaserver;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
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.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
@SpringBootApplication
@EnableDiscoveryClient
@EnableHystrix
@EnableHystrixDashboard
public class HepServiceRibbonHystrix {
    public static void main(String[] args) {
        SpringApplication.run(HepServiceRibbonHystrix.class, args);
    }
    @Bean
    public IRule ribbonRule() {
        // 负载均衡规则，改为随机
        return new RandomRule();
    }
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

首先调用一下http://localhost:8005/consumerEurekaClient，然后调用http://localhost:8005/actuator/hystrix.stream，可以看到ping的信息

输入http://localhost:8005/hystrix/，把刚刚的地址http://localhost:8005/actuator/hystrix.stream贴进来。

点击进去，可以看到dashboard信息了