springcloud+eureka+Ribbon+Hystrix

朱雀 2022-03-30 11:15 221阅读 0赞

## 1 分布式系统面临的问题 ##

复杂分布式体系结构中的应用程序有数十个依赖关系，每个依赖关系在某些时候将不可避免地失败。

### 服务雪崩 ###

多个微服务之间调用的时候，假设微服务A调用微服务B和微服务C，微服务B和微服务C又调用其它的微服务，这就是所谓的“扇出”。如果扇出的链路上某个微服务的调用响应时间过长或者不可用，对微服务A的调用就会占用越来越多的系统资源，进而引起系统崩溃，所谓的“雪崩效应”.  
对于高流量的应用来说，单一的后端依赖可能会导致所有服务器上的所有资源都在几秒钟内饱和。比失败更糟糕的是，这些应用程序还可能导致服务之间的延迟增加，备份队列，线程和其他系统资源紧张，导致整个系统发生更多的级联故障。这些都表示需要对故障和延迟进行隔离和管理，以便单个依赖关系的失败，不能取消整个应用程序或系统。

## 2 Hystrix ##

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、不必要地占用，从而避免了故障在分布式系统中的蔓延，乃至雪崩。  
Hystrix的作用：服务降级，服务熔断，服务限流，接近实时的监控

## 3 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，会进行服务的降级，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。  
注意：  
服务熔断是在服务端完成，与客户端无关。

代码如下：  
总共四个服务  
microservicecloud-api  
microservicecloud-Eureka-7001  
microservicecloud-provider-dept-hystrix-8888（重点）  
microservicecloud-consumer-dept-80

### microservicecloud-provider-dept-hystrix-8888服务 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1MjM3NDYzMzU4Mw_size_16_color_FFFFFF_t_70]  
pom.xml

<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.wuk.springcloud</groupId>
        <artifactId>microservicecloud</artifactId>
        <version>0.0.1-SNAPSHOT</version>
      </parent>
      <artifactId>microservicecloud-provider-dept-hystrix-8888</artifactId>
      <dependencies>
       
       <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-hystrix</artifactId>
       </dependency>
       
       <dependency>
         <groupId>com.wuk.springcloud</groupId>
         <artifactId>microservicecloud-api</artifactId>
         <version>${project.version}</version>
       </dependency>
       
       <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-eureka</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-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>

application.yml

server:
      port: 8888
      
    mybatis:
      config-location: classpath:mybatis/mybatis.cfg.xml        # mybatis配置文件所在路径
      type-aliases-package: com.wuk.entity    # 所有Entity别名类所在包
      mapper-locations: 
      - classpath:mybatis/mapper/**/*.xml
       
    spring:
       application:
        name: producers    #注册在eureka上的服务名称,后续消费方访问要用它,如果多个服务负载均衡，就要保持一致
       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://127.0.0.1:3306/cloudDB01              # 数据库名称
        username: root
        password: 123456
        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://localhost:7001/eureka
      instance:
        instance-id: microservicecloud-dept-hystrix-8888 #自定义服务名称 
        prefer-ip-address: true #显示服务ip

DeptController.java

package com.wuk.controller;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    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.wuk.entity.Dept;
    import com.wuk.service.DeptService;
    
    @RestController
    public class DeptController { 
    
    	 @Autowired
    	  private DeptService service;
    	  
    	  @RequestMapping(value="/dept/add",method=RequestMethod.POST)
    	  public boolean add(@RequestBody  Dept dept)
    	  { 
    	   return service.add(dept);
    	  }
    	  
    	  //@PathVariable 表示直接从url里面取数据 
    	  //@RequestBody 表示数据json
    	  @HystrixCommand(fallbackMethod="processHystrix_get")
    	  @RequestMapping(value="/dept/get/{id}",method=RequestMethod.GET)
    	  public Dept get(@PathVariable("id") Long id)
    	  { 
    		  Dept dept =  this.service.get(id);
    		   if(null == dept)
    		   { 
    			  //只有当抛出异常时候才会有用
    		     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) { 
    		  
    		  Dept errorObj=new Dept();
    		  errorObj.setDeptno(id);
    		  errorObj.setdName("该id="+id+"对应的信息不存在");
    		  errorObj.setDb_source("没有对应的数据库源");
    		  
    		  return errorObj;
    	  }
    	  
    	  @RequestMapping(value="/dept/list",method=RequestMethod.GET)
    	  public List<Dept> list()
    	  { 
    	   return service.list();
    	  }
    }

DeptProviderHystrix8888\_APP.java

剩下的代码同上一篇。

## 4 服务降级 ##

### 含义： ###

整体资源快不够了，忍痛将某些服务先关掉，待渡过难关，再开启回来。  
注意：  
服务降级处理是在客户端实现完成的，与服务端没有关系。  
代码如下：  
总共四个服务  
microservicecloud-api（重点）  
microservicecloud-dept-8888  
microservicecloud-consumer-dept-feign（重点）  
microservicecloud-Eureka-7001

### （1）microservicecloud-api ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1MjM3NDYzMzU4Mw_size_16_color_FFFFFF_t_70 1]  
DeptClientServiceFallbackFactory.java

package com.wuk.service.impl;
    
    import java.util.List;
    
    import org.springframework.stereotype.Component;
    
    import com.wuk.entity.Dept;
    import com.wuk.service.DeptClientService;
    
    import feign.hystrix.FallbackFactory;
    
    @Component//不要忘记添加
    public class DeptClientServiceFallbackFactory implements FallbackFactory<DeptClientService> { 
    
    	@Override
    	public DeptClientService create(Throwable cause) { 
    		
    		
    		return new DeptClientService() { 
    
    			@Override
    			public Dept get(long id) { 
    				
    				Dept dept=new Dept();
    				dept.setDeptno(id);
    				dept.setdName("该ID："+id+"没有没有对应的信息,Consumer客户端提供的降级信息,此刻服务Provider已经关闭");
    				dept.setDb_source("no this database in MySQL");
    				return dept;
    			}
    
    			@Override
    			public List<Dept> list() { 
    				// TODO Auto-generated method stub
    				return null;
    			}
    
    			@Override
    			public boolean add(Dept dept) { 
    				// TODO Auto-generated method stub
    				return false;
    			}
    
    		};
    	}
    
    }

DeptClientService.java

package com.wuk.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.wuk.entity.Dept;
    import com.wuk.service.impl.DeptClientServiceFallbackFactory;
    
    
    @FeignClient(value = "producers",fallbackFactory=DeptClientServiceFallbackFactory.class)
    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);
    
    }

### (2)microservicecloud-consumer-dept-feign ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1MjM3NDYzMzU4Mw_size_16_color_FFFFFF_t_70 2]  
application.yml

server:
      port: 80
    feign: 
      hystrix: 
        enabled: true
    eureka:
      client:
        register-with-eureka: false
        service-url: 
          defaultZone: http://127.0.0.1:7001/eureka/

测试办法：当我们关掉服务方，消费方调用会有如下提示：  
![在这里插入图片描述][20190105215605858.png]

剩下代码见案例

## 5 服务监控hystrixDashboard ##

### （1）概述 ###

除了隔离依赖服务的调用以外，Hystrix还提供了准实时的调用监控（Hystrix Dashboard），Hystrix会持续地记录所有通过Hystrix发起的请求的执行信息，并以统计报表和图形的形式展示给用户，包括每秒执行多少请求多少成功，多少失败等。Netflix通过hystrix-metrics-event-stream项目实现了对以上指标的监控。Spring Cloud也提供了Hystrix Dashboard的整合，对监控内容转化成可视化界面。  
代码如下：  
microservicecloud-api  
microservicecloud-Eureka-7001  
microservicecloud-consumer-hystrix-dashboard（重点）  
microservicecloud-provider-dept-hystrix-8888（重点）

### （1）microservicecloud-consumer-hystrix-dashboard ###

pom.xml

<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.wuk.springcloud</groupId>
        <artifactId>microservicecloud</artifactId>
        <version>0.0.1-SNAPSHOT</version>
      </parent>
      <artifactId>microservicecloud-consumer-hystrix-dashboard</artifactId>
      <dependencies>
       
       <dependency>
         <groupId>com.wuk.springcloud</groupId>
         <artifactId>microservicecloud-api</artifactId>
         <version>${project.version}</version>
       </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>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.cloud</groupId>
         <artifactId>spring-cloud-starter-feign</artifactId>
       </dependency>
       
       <dependency>
           <groupId>org.springframework.cloud</groupId>
           <artifactId>spring-cloud-starter-hystrix</artifactId>
       </dependency>
       <dependency>
           <groupId>org.springframework.cloud</groupId>
           <artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
       </dependency> 
          
       <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-actuator</artifactId>
       </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        <version>2.0.2.RELEASE</version>
    </dependency>
      </dependencies>
    </project>

DeptConsumer\_DashBoard\_App.java

### (2) microservicecloud-provider-dept-hystrix-8888 ###

pom.xml

<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.wuk.springcloud</groupId>
    		<artifactId>microservicecloud</artifactId>
    		<version>0.0.1-SNAPSHOT</version>
    	</parent>
    	<artifactId>microservicecloud-provider-dept-hystrix-8888</artifactId>
    	<dependencies>
    
    		
    		<dependency>
    			<groupId>com.wuk.springcloud</groupId>
    			<artifactId>microservicecloud-api</artifactId>
    			<version>${project.version}</version>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-eureka</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-config</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>
    		
    		<dependency>
    			<groupId>org.springframework.cloud</groupId>
    			<artifactId>spring-cloud-starter-hystrix</artifactId>
    		</dependency>
    		
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-actuator</artifactId>
    		</dependency>
    	</dependencies>
    </project>

application.yml

server:
      port: 8889
      
    mybatis:
      config-location: classpath:mybatis/mybatis.cfg.xml        # mybatis配置文件所在路径
      type-aliases-package: com.wuk.entity    # 所有Entity别名类所在包
      mapper-locations: 
      - classpath:mybatis/mapper/**/*.xml
       
    spring:
       application:
        name: producers    #注册在eureka上的服务名称,后续消费方访问要用它,如果多个服务负载均衡，就要保持一致
       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://127.0.0.1:3306/cloudDB01              # 数据库名称
        username: root
        password: 123456
        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://localhost:7001/eureka
      instance:
        instance-id: microservicecloud-dept-hystrix-8888 #自定义服务名称 
        prefer-ip-address: true #显示服务ip

DeptProviderHystrix8888\_APP.java

package com.wuk;
    
    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
    @EnableCircuitBreaker//对hystrixR熔断机制的支持
    //@EnableDiscoveryClient//服务发现
    //@EnableDiscoveryClient和@EnableEurekaClient共同点就是：都是能够让注册中心能够发现，扫描到改服务。
    //不同点：@EnableEurekaClient只适用于Eureka作为注册中心，@EnableDiscoveryClient 可以是其他注册中心。
    
    public class DeptProviderHystrix8888_APP { 
    
    	public static void main(String[] args) { 
    
    		SpringApplication.run(DeptProviderHystrix8888_APP.class, args);
    	}
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1MjM3NDYzMzU4Mw_size_16_color_FFFFFF_t_70]: /images/20220330/b8b052537b3243089cef0136e619d44d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d1MjM3NDYzMzU4Mw_size_16_color_FFFFFF_t_70 1]: /images/20220330/a80deb886dbc45118f17273ec6ac2bb7.png
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[20190105215605858.png]: /images/20220330/09c32d934bf9436da68309064a0a99db.png

springcloud+eureka+Ribbon+Hystrix

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