16.Hystrix 实例（springcloud）

1.2 服务雪崩怎么解决

1.2.1 修改调用的超时时长（不推荐）

将服务间的调用超时时长改小，这样就可以让线程及时回收，保证服务可用

优点：非常简单，也可以有效的解决服务雪崩

缺点： 不够灵活 ，有的服务需要更长的时间去处理（写库，整理数据）

1.2.2 设置拦截器

2.Spring Cloud Hystrix 简介

熔断器，也叫断路器！（正常情况下 断路器是关的 只有出了问题才打开）用来 保护微服务不雪崩的方法 。思想和我们上面画的拦截器一样。

Hystrix 是 Netflix 公司开源的一个项目，它提供了熔断器功能，能够阻止 分布式系统中出现联动故障 。Hystrix 是通过隔离服务的访问点阻止联动故障的，并提供了故障的解决方案，从

而提高了整个分布式系统的弹性。微博   弹性云扩容    Docker K8s

3.Hystrix 快速入门

当有服务调用的时候，才会出现服务雪崩，所以 Hystrix 常和 OpenFeign ， Ribbon 一起出现

2.application.yml配置文件

server:
  port: 8080
spring:
  application:
    name: register-service
eureka:
  client:
    service-url:
      defaultZone: http://192.168.174.133:8761/eureka
  instance:
    hostname: localhost
    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}

 3.创建一个controller类

package com.it.controller;
 
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
public class RegisterController {
 
    @GetMapping("register")
    public String register(){
        return "注册成功";
    }
 
}

 4.启动主函数类

package com.it;
 
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
 
@SpringBootApplication
@EnableEurekaClient
public class RegisterService02Application {
 
    public static void main(String[] args) {
        SpringApplication.run(RegisterService02Application.class, args);
    }
 
}

        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-hystrixartifactId>
        dependency>

"1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0modelVersion>
    <parent>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-parentartifactId>
        <version>2.3.12.RELEASEversion>
        <relativePath/> 
    parent>
    <groupId>com.itgroupId>
    <artifactId>customer-service-1artifactId>
    <version>0.0.1-SNAPSHOTversion>
    <name>customer-service-1name>
    <description>Demo project for Spring Bootdescription>
    <properties>
        <java.version>1.8java.version>
        <spring-cloud.version>Hoxton.SR12spring-cloud.version>
    properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-webartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-eureka-clientartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-openfeignartifactId>
        dependency>
 
        <dependency>
            <groupId>org.springframework.cloudgroupId>
            <artifactId>spring-cloud-starter-netflix-hystrixartifactId>
        dependency>
 
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starter-testartifactId>
            <scope>testscope>
        dependency>
    dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloudgroupId>
                <artifactId>spring-cloud-dependenciesartifactId>
                <version>${spring-cloud.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>
        dependencies>
    dependencyManagement>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-maven-pluginartifactId>
            plugin>
        plugins>
    build>
 
project>

server:
  port: 8081
spring:
  application:
    name: customer-service
eureka:
  client:
    service-url:
      defaultZone: http://192.168.174.133:8761/eureka
  instance:
    hostname: localhost
    instance-id: ${eureka.instance.hostname}:${spring.application.name}:${server.port}
feign:
  hystrix:
    enabled: true #在springcloud的F版本以前是默认开启的

3.创建CustomerRegisterFeign接口

@FeignClient需要指定访问失败的路径，即熔断路径

package com.it.feign;
 
import com.it.feign.hystrix.CustomerRegisterFeignHystrix;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
 
/**
 * 这里需要指定熔断类
 */
@FeignClient(value = "register-service",fallback = CustomerRegisterFeignHystrix.class)
public interface CustomerRegisterFeign {
 
    @GetMapping("register")
    public String register();
 
}

4.CustomerRegisterFeignHystrix熔断类，实现CustomerRegisterFeign接口

package com.it.feign.hystrix;
 
import com.it.feign.CustomerRegisterFeign;
import org.springframework.stereotype.Component;
//这里需要加入ioc容器的注解
@Component
public class CustomerRegisterFeignHystrix implements CustomerRegisterFeign {
    @Override
    public String register() {
        return "我是备选方案！";
    }
}

5.CustomerController类

进行远程调用

package com.it.controller;
 
import com.it.feign.CustomerRegisterFeign;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
 
import javax.annotation.Resource;
 
@RestController
public class CustomerController {
 
    @Resource
    private CustomerRegisterFeign customerRegisterFeign;
 
    @GetMapping("customer")
    public String customer(){
        System.out.println("用户进行账号注册");
        //RPC
        String register = customerRegisterFeign.register();
        System.out.println(register);
        return register;
    }
 
}

6.主函数启动类

package com.it;
 
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
 
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class CustomerService1Application {
 
    public static void main(String[] args) {
        SpringApplication.run(CustomerService1Application.class, args);
    }
 
}

7.测试

7.1关闭register-service,只启动该项目查看是否会发生熔断，进入熔断类中的方法

结论：成功进入

7.2打开register-service,查看该项目是否会正常的发起远程调用

结论：正常发起远程调用