Spring Cloud 之Ribbon负载均衡

落日映苍穹つ 2022-12-16 06:27 211阅读 0赞

推荐：[微服务汇总][Link 1]

## Spring Cloud 之Ribbon负载均衡 ##

简单来讲，Ribbon的主要功能是提供客户端的负载均衡。它可以在客户端配置服务名称（服务名称由注册中心维护），然后通过负载均衡算法来确定请求哪个服务（一个服务名称可能有多个服务实例），从而实现客户端负载均衡。

我们这里会涉及到Eureka注册中心，两个服务提供者(server-provider)，一个服务消费者（server-consumer）。

创建Eureka注册中心。

`pom.xml`如下：

<?xml version="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>4.0.0</modelVersion>
    
        <groupId>com.kaven</groupId>
        <artifactId>eureka</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>eureka</name>
        <description>Demo project for Spring Boot</description>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
            <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
            <java.version>1.8</java.version>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    </project>

`application.yml`如下：

eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/
        register-with-eureka: false
      server:
        enable-self-preservation: true
    
    spring:
      application:
        name: eureka
    
    server:
      port: 8761

启动类：

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

启动注册中心。

创建第一个server-provider。  
`pom.xml`如下：

<?xml version="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>4.0.0</modelVersion>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.kaven</groupId>
        <artifactId>server-provider</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>server-provider</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    </project>

其实在引入eureka-client时就已经默认引入了ribbon。

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

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70]

`application.yml`如下：

spring:
      application:
        name: server-provider
    
    server:
      port: 8001
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/

启动类：

package com.kaven.server;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    public class ServerProviderApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(ServerProviderApplication.class, args);
        }
    }

接口：

package com.kaven.server.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class MessageServerController { 
    
        @GetMapping("/getMessage")
        public String getMessage(){ 
            return "hello , Jack";
        }
    }

创建第二个server-provider。  
`pom.xml`如下：

<?xml version="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>4.0.0</modelVersion>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.kaven</groupId>
        <artifactId>server-provider</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>server-provider</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    </project>

`application.yml`如下：

spring:
      application:
        name: server-provider
    
    server:
      port: 8002
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/

启动类：

接口：

创建server-consumer。  
`pom.xml`如下：

<?xml version="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>4.0.0</modelVersion>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.0.6.RELEASE</version>
            <relativePath/> 
        </parent>
    
        <groupId>com.kaven</groupId>
        <artifactId>server-consumer</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    
        <name>server-consumer</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
            <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    </project>

`application.yml`如下：

spring:
      application:
        name: server-consumer
    
    
    server:
      port: 8003
    
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8761/eureka/

启动类：

package com.kaven.client;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    
    
    @SpringBootApplication
    @EnableDiscoveryClient
    public class ServerConsumerApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(ServerConsumerApplication.class, args);
        }
    }

RestTemplate组件（用来进行服务间相互请求）：

package com.kaven.client.component;
    
    import org.springframework.cloud.client.loadbalancer.LoadBalanced;
    import org.springframework.context.annotation.Bean;
    import org.springframework.stereotype.Component;
    import org.springframework.web.client.RestTemplate;
    
    @Component
    public class RestTemplateComponent { 
    
        @Bean
        @LoadBalanced
        public RestTemplate restTemplate(){ 
            return new RestTemplate();
        }
    }

之前有介绍过使用RestTemplate来实现微服务之间相互请求的方式：[Spring Cloud 之使用RestTemplate实现微服务之间相互请求的三种方式][Spring Cloud _RestTemplate]，`@LoadBalanced`注解提供了负载均衡的功能，默认负载均衡算法是轮询，`@LoadBalanced`跟Ribbon的关系，到最后会进行说明。

接口：

package com.kaven.client.controller;
    
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.client.RestTemplate;
    
    import javax.annotation.Resource;
    
    @RestController
    public class MessageController{ 
    
        @Resource
        private RestTemplate restTemplate;
    
        @GetMapping("/getMessage")
        public String getMessage(){ 
    
            String message = "get: " + restTemplate.getForObject("http://server-provider/getMessage" , String.class);
            System.out.println(message);
            return message;
        }
    }

`http://server-provider/getMessage`中的`server-provider`是服务提供者注册在注册中心的服务名称。

访问`http://localhost:8761/`，可以看到注册中心的信息，并且三个服务也全部注册上来了。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 1]

访问`http://localhost:8003/getMessage`多次，server-consumer服务的控制台打印如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 2]

这也说明`@LoadBalanced`注解默认负载均衡算法是轮询。

接下来，我们来试着自定义负载均衡算法。

Spring Cloud提供了Ribbon负载均衡的默认选择（轮询），当然我们也可以选择其他的负载均衡策略，首先在server-consumer服务添加一个配置类：

package com.kaven.client.config;
    
    import com.netflix.loadbalancer.IRule;
    import com.netflix.loadbalancer.RandomRule;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    public class RibbonConfig { 
    
        /** * 使用随机的轮询方法 */
        @Bean
        public IRule iRule() { 
            return new RandomRule();
        }
    }

再在server-consumer服务的启动类上添加`@RibbonClient`注解，

package com.kaven.client;
    
    import com.kaven.client.config.RibbonConfig;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.ribbon.RibbonClient;
    
    @SpringBootApplication
    @EnableDiscoveryClient
    @RibbonClient(name = "server-provider",configuration = RibbonConfig.class)
    public class ServerConsumerApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(ServerConsumerApplication.class, args);
        }
    }

`@RibbonClient(name = "server-provider",configuration = RibbonConfig.class)` ：

*  name：是服务提供者注册在Eureka的服务名称。
 *  configuration ：是我们自定义的配置类。

重新启动server-consumer服务。

访问`localhost:8003/getMessage`多次，得到server-consumer服务的控制台打印如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70 3]  
很明显看得出来负载均衡策略是随机，这也说明了我们自定义配置生效了，也可以知道`@LoadBalanced`注解实现客户端负载均衡的底层还是使用了Ribbon组件，因为我们这里更改了默认的Ribbon负载均衡配置，而且通过使用`@LoadBalanced`注解生效了。

Spring Cloud的Ribbon负载均衡就介绍到这里。

写博客是博主记录自己的学习过程，如果有错误，请指正，谢谢！

[Link 1]: https://kaven.blog.csdn.net/article/details/109063924
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3OTYwNjAz_size_16_color_FFFFFF_t_70]: /images/20221123/f01851961eab4ffd9f9e01b3a7b84117.png
[Spring Cloud _RestTemplate]: https://kaven.blog.csdn.net/article/details/109103275
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