Springcloud（四）负载均衡feign与Hystrix断路器

今天药忘吃喽~ 2022-03-27 21:07 255阅读 0赞

# springcloud学习总结 #

## 4、负载均衡feign与Hystrix断路器 ##

**一、ribbon与feign有什么区别？**

Ribbon  
Ribbon 是一个基于 HTTP 和 TCP 客户端的负载均衡器

它可以在客户端配置 ribbonServerList（服务端列表），然后轮询请求以实现均衡负载

它在联合 Eureka 使用时

ribbonServerList 会被 DiscoveryEnabledNIWSServerList 重写，扩展成从 Eureka 注册中心获取服务端列表

同时它也会用 NIWSDiscoveryPing 来取代 IPing，它将职责委托给 Eureka 来确定服务端是否已经启动

Feign  
Spring Cloud Netflix 的微服务都是以 HTTP 接口的形式暴露的，所以可以用 Apache 的 HttpClient 或 Spring 的 RestTemplate 去調用

而 Feign 是一個使用起來更加方便的 HTTP 客戶端，它用起來就好像調用本地方法一樣，完全感覺不到是調用的遠程方法

总结起来就是：发布到注册中心的服务方接口，是 HTTP 的，也可以不用 Ribbon 或者 Feign，直接浏览器一样能够访问

只不过 Ribbon 或者 Feign 调用起来要方便一些，最重要的是：它俩都支持软负载均衡

注意：spring-cloud-starter-feign 里面已经包含了 spring-cloud-starter-ribbon（Feign 中也使用了 Ribbon）  
**二、feign的使用**  
**新建consumerfeign模块**

**修改pom文件增加依赖**

<dependencies>
           <dependency>
               <groupId>springcloud</groupId>
               <artifactId>springcloud-api</artifactId>
               <version>${ project.version}</version>
           </dependency>
           <dependency>
               <groupId>org.springframework.cloud</groupId>
               <artifactId>spring-cloud-starter-feign</artifactId>
           </dependency>
           
           <dependency>
               <groupId>org.springframework.cloud</groupId>
               <artifactId>spring-cloud-starter-eureka</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.cloud</groupId>
               <artifactId>spring-cloud-starter-ribbon</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.cloud</groupId>
               <artifactId>spring-cloud-starter-config</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-starter-web</artifactId>
           </dependency>
           
           <dependency>
               <groupId>org.springframework</groupId>
               <artifactId>springloaded</artifactId>
           </dependency>
           <dependency>
               <groupId>org.springframework.boot</groupId>
               <artifactId>spring-boot-devtools</artifactId>
           </dependency>
           <dependency>
               <groupId>springcloud</groupId>
               <artifactId>springcloud-api</artifactId>
               <version>1.0-SNAPSHOT</version>
           </dependency>
       </dependencies>

**新建application.yml文件**

server:
      port: 80
      
    
    feign:
      hystrix:
        enabled: true
    
    
    
    eureka:
      client:
        register-with-eureka: false
        service-url: 
          defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/

**服务消费处理器（controller）**

package com.atguigu.springcloud.controller;
    
    import java.util.List;
    
    import com.atguigu.springcloud.entities.Dept;
    import com.atguigu.springcloud.service.DeptClientService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class DeptController_Consumer
    { 
    	@Autowired
    	private DeptClientService service;
    
    	@RequestMapping(value = "/consumer/dept/get/{id}")
    	public Dept get(@PathVariable("id") Long id)
    	{ 
    		return this.service.get(id);
    	}
    
    	@RequestMapping(value = "/consumer/dept/list")
    	public List<Dept> list()
    	{ 
    		return this.service.list();
    	}
    
    	@RequestMapping(value = "/consumer/dept/add")
    	public Object add(Dept dept)
    	{ 
    		return this.service.add(dept);
    	}
    }

**新建配置类**

package com.atguigu.springcloud.cfgbeans;
    
    import org.springframework.cloud.client.loadbalancer.LoadBalanced;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.client.RestTemplate;
    
    import com.netflix.loadbalancer.IRule;
    import com.netflix.loadbalancer.RetryRule;
    
    @Configuration
    public class ConfigBean {  
    	@Bean
    	public IRule myRule()
    	{ 
    		//return new RoundRobinRule();
    		//return new RandomRule();//达到的目的，用我们重新选择的随机算法替代默认的轮询。
    		return new RetryRule();
    	}
    }

**主启动类**

package com.atguigu.springcloud;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.cloud.netflix.feign.EnableFeignClients;
    import org.springframework.context.annotation.ComponentScan;
    
    @SpringBootApplication
    @EnableEurekaClient
    @EnableFeignClients(basePackages= { "com.atguigu.springcloud"})
    @ComponentScan("com.atguigu.springcloud")
    public class DeptConsumer80_Feign_App
    { 
    	public static void main(String[] args)
    	{ 
    		SpringApplication.run(DeptConsumer80_Feign_App.class, args);
    	}
    }

**修改api模块，新增service包以及新建接口**

package com.atguigu.springcloud.service;
    
    import java.util.List;
    
    import org.springframework.cloud.netflix.feign.FeignClient;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import com.atguigu.springcloud.entities.Dept;
    @FeignClient(value = "MICROSERVICECLOUD-DEPT")
    public interface DeptClientService
    { 
    	@RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
    	public Dept get(@PathVariable("id") long id);
    
    	@RequestMapping(value = "/dept/list", method = RequestMethod.GET)
    	public List<Dept> list();
    
    	@RequestMapping(value = "/dept/add", method = RequestMethod.POST)
    	public boolean add(Dept dept);
    }

**启动注册中心、提供者与此消费者查看结果**  
[http://localhost:80/consumer/dept/list][http_localhost_80_consumer_dept_list]

**三、Hystrix的出现以及使用**

**为什么会出现**

在微服务架构中，根据业务来拆分成一个个的服务，服务与服务之间可以相互调用（RPC） 。为了保证其高可用，单个服务通常会集群部署。由于网络原因或者自身的原因，服务并不能保证100%可用，如果单个服务出现问题，调用这个服务就会出现线程阻塞，此时若有大量的请求涌入，Servlet容器的线程资源会被消耗完毕，导致服务瘫痪。服务与服务之间的依赖性，故障会传播，会对整个微服务系统造成灾难性的严重后果，这就是服务故障的“雪崩”效应。

**初始接触**

**新建模块hystrix**

**pom**

<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>springcloud</groupId>
                <artifactId>springcloud-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>

**application**

server:
      port: 8001
      
    mybatis:
      config-location: classpath:mybatis/mybatis.cfg.xml  #mybatis所在路径
      type-aliases-package: com.atguigu.springcloud.entities #entity别名类
      mapper-locations:
      - classpath:mybatis/mapper/**/*.xml #mapper映射文件
        
    spring:
       application:
        name: microservicecloud-dept 
       datasource:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/cloudDB01
        username: root
        password: 123321
        dbcp2:
          min-idle: 5
          initial-size: 5
          max-total: 5
          max-wait-millis: 200
          
    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/
      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: atguigu-microservicecloud
      company.name: www.atguigu.com
      build.artifactId: $project.artifactId$
      build.version: $project.version$

**拷贝provider8001的mapper.xml、dao、service、controller**

**修改controller**

package com.atguigu.springcloud.controller;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RestController;
    
    import com.atguigu.springcloud.entities.Dept;
    import com.atguigu.springcloud.service.DeptService;
    import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
    
    @RestController
    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")
    	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;
    	}
    
    	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");
    	}
    }

**新建主启动类**

package com.atguigu.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);
    	}
    }

**启动注册中心，hystrix与服务消费者,输入数据库存在的id与不存在的，查看输出**  
[http://localhost:80/consumer/dept/get/\{id\}][http_localhost_80_consumer_dept_get_id]

**后续：hystrix模块的问题与改进，视图监控界面的使用…**

[http_localhost_80_consumer_dept_list]: http://localhost:80/consumer/dept/list
[http_localhost_80_consumer_dept_get_id]: http://localhost:80/consumer/dept/get/%7Bid%7D