搭建springcloud的demo之Hystrix服务熔断 (七)

柔光的暖阳◎ 2022-03-02 03:48 190阅读 0赞

## 标题 ##

**Hystrix是一个用于处理分布式系统的延迟和容错的开源库,在分布式系统里,许多依赖不可避免的会调用失败,比如超时,异常等,Hystrix能够保证在一个依赖出问题的情况下,不会导致整体服务失败,避免级联故障,以提高分布式系统的弹性;**

**"断路器"本身是一种开关装置,当某个服务单元发生故障之后,通过断路器的故障监控(类似熔断保险丝),向调用方返回一个符合预期的,可处理的备选响应(FallBack),而不是长时间的等待或者抛出调用方无法处理的异常,这样就保证了服务调用方的线程不会被长时间,不必要的占用,从而避免了故障在分布式系统中的蔓延,乃至雪崩;**

**服务熔断**  
**熔断机制是应对雪崩效应的一种微服务链路保护机制;**  
**当扇出链路的某个微服务不可用或者响应时间太长时,会进行服务的将几,进而熔断该节点微服务的调用,快速返回"错误"的响应信息,当检测到该节点微服务调用响应正常后恢复调用链路,在springcloud框架里熔断机制通过Hystrix实现,Hystrix会监控微服务间调用的状况,当失败的调用到一定阈值,缺省是5秒内20次调用失败就会启动熔断机制,熔断机制的注解是@HystrixCommand**

## 创建microservicecloud-provider-dept-hystrix-8001 ##

## 编写microservicecloud-provider-dept-hystrix-8001的pom.xml ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70]

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    	<parent>
    		<groupId>com.yt.springcloud</groupId>
    		<artifactId>microservicecloud</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</parent>
    	<artifactId>microservicecloud-provider-dept-hystrix-8001</artifactId>
    	
    	<dependencies>
    		
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-hystrix</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-eureka</artifactId>
    		</dependency>
    		 
    	  	<dependency>
    	  		<groupId>com.yt.springcloud</groupId> 
    	  		<artifactId>microservicecloud-api</artifactId>
    	  		<version>${project.version}</version>
    	  	</dependency>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-config</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-actuator</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>junit</groupId>
    			<artifactId>junit</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>mysql</groupId>
    			<artifactId>mysql-connector-java</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>com.alibaba</groupId>
    			<artifactId>druid</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>ch.qos.logback</groupId>
    			<artifactId>logback-core</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.mybatis.spring.boot</groupId>
    			<artifactId>mybatis-spring-boot-starter</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-jetty</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-test</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework</groupId>
    			<artifactId>springloaded</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-devtools</artifactId>
    		</dependency>
    	</dependencies>
    
    </project>

## 编写microservicecloud-provider-dept-hystrix-8001的application.yml ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 1]

server:
      port: 8001                                         # 当前微服务的端口
      
    mybatis:
      config-location: classpath:mybatis/mybatis.cfg.xml # mybatis配置文件所在路径
      type-aliases-package: com.yt.springcloud.entity    # 所有饿entity实体类所在包
      mapper-locations:
      - classpath:mybatis/mapper/**/*.xml                # mapper映射文件
    
    spring:
      application:
       name: microservicecloud-dept                      # 对外暴露的微服务的名字(很重要)
      datasource:
       type: com.alibaba.druid.pool.DruidDataSource      # 当前数据源操作类型
       driver-class-name: org.gjt.mm.mysql.Driver        # mysql驱动包
       url: jdbc:mysql://localhost:3306/cloudDB01        # 数据库名称
       username: root
       password: hannong
       dbcp2:
        min-idle: 5                                      # 数据库连接池的最小维持连接数 
        initial-size: 5                                  # 初始化连接数
        max-total: 5                                     # 最大连接数
        max-wait-millis: 200                             # 等待连接获取的最大超时时间
        
    eureka:
       client:   #客户端注册进eureka服务列表内
        service-url:
          defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/      #去注册中心的地址
          #defaultZone:7001,7002,7003 去注册中心的地址
       instance: 
          instance-id: microservicecloud-dept8001-hystrix #自定义hystrix相关的服务名称信息
          prefer-ip-address: true                         #访问路径可以显示ip地址
    
    info:
       app.name: yt-microservicecloud                     #
       company.name: www.yt.com                           #
       build.artifactId: $project.artifactId$             #
       build.version: $project.version$                   #

## 修改DeptController ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 2]

package com.yt.springcloud.controller;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.client.discovery.DiscoveryClient;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
    import com.yt.springcloud.entity.Dept;
    import com.yt.springcloud.service.impl.DeptService;
    
    @RestController//整合了responceBody+Controller
    public class DeptController {
    
    	@Autowired
    	private DeptService service = null;
    
    	@RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
    	//一旦调用服务方法失败并抛出了错误信息后，会自动调用@HystrixCommand标注好的fallbackMethod调用类中的指定方法
    	@HystrixCommand(fallbackMethod = "processHystrix_Get")//发生异常的时候,会调用这个fallbackmethod方法,去处理
    	public Dept get(@PathVariable("id") Long id){
    
    		Dept dept = this.service.get(id);
    		
    		if (null == dept) {
    			throw new RuntimeException("该ID：" + id + "没有没有对应的信息");
    		}
    		
    		return dept;
    	}
    
    	/**
    	 * 发生异常的时候,会调用这个方法来处理,还是返回一个dept对象,但是里面的信息是我们自定义的
    	 * @param id
    	 * @return
    	 */
    	public Dept processHystrix_Get(@PathVariable("id") Long id){
    		return new Dept().setDeptno(id).setDname("该ID：" + id + "没有没有对应的信息,null--@HystrixCommand")
    				.setDb_source("no this database in MySQL");
    	}
    	
    	
    }

## 实体类的链式风格异常,要安装lombok的插件 ##

**[https://blog.csdn.net/yuanting\_/article/details/88667206][https_blog.csdn.net_yuanting_article_details_88667206]**

## 修改主启动类DeptProvider8001-Hystrix\_App并添加新注解@EnableCircuitBre ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 3]

package com.yt.springcloud;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    
    @SpringBootApplication
    @EnableEurekaClient //本服务启动后会自动注册进eureka服务中
    @EnableDiscoveryClient //服务发现
    @EnableCircuitBreaker//对hystrixR熔断机制的支持!!!
    public class DeptProvider8001_Hystrix_App
    {
    	public static void main(String[] args)
    	{
    		SpringApplication.run(DeptProvider8001_Hystrix_App.class, args);
    	}
    }

## 测试 ##

3个eureka先启动  
主启动类DeptProvider8001\_Hystrix\_App  
启动microservicecloud-consumer-dept-80

## 路径:[http://localhost:7001/][http_localhost_7001] ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 4]

## 测试id为1,数据是OK的 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 5]

## 当的id不存在的时候,会进入容错的方法,返回刚刚设置的返回值 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 6]

## 总结 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 7]

翻译于尚硅谷周阳老师:[https://www.bilibili.com/video/av22613028?from=search&seid=11377756339718254280][https_www.bilibili.com_video_av22613028_from_search_seid_11377756339718254280]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70]: /images/20220302/328cb606c18848d38e6bfd35bb1a7496.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 1]: /images/20220302/249392ec2c794b729458253c35095e7b.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 2]: /images/20220302/314ac81c122f409591866dcfdd33cf62.png
[https_blog.csdn.net_yuanting_article_details_88667206]: https://blog.csdn.net/yuanting_/article/details/88667206
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 3]: /images/20220302/eac407ee947e44b4bb2528935cd6dfb6.png
[http_localhost_7001]: http://localhost:7001/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 4]: /images/20220302/4d5e2d9d49434a5e819802cdc8baf7a9.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 5]: /images/20220302/1a8d37a34874436f96ca3146ecfafa08.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 6]: /images/20220302/701aa306fbda4fb2bab27811f7aa48b8.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3l1YW50aW5nXw_size_16_color_FFFFFF_t_70 7]: /images/20220302/4f5536246e334ca6881466e20c9e1c92.png
[https_www.bilibili.com_video_av22613028_from_search_seid_11377756339718254280]: https://www.bilibili.com/video/av22613028?from=search&seid=11377756339718254280