Spring Cloud 之Ribbon负载均衡

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ITKaven 2022-11-09 19:38:15 博主文章分类：后端框架 ©著作权

文章标签 java 后端 spring boot spring maven 文章分类 负载均衡服务器

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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/> <!-- lookup parent from repository -->
    </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/> <!-- lookup parent from repository -->
    </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>

Spring Cloud 之Ribbon负载均衡_java

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/> <!-- lookup parent from repository -->
    </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：

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 , Kaven";
    }
}

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/> <!-- lookup parent from repository -->
    </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，@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。

Spring Cloud 之Ribbon负载均衡_java_02

访问http://localhost:8003/getMessage多次，server-consumer服务的控制台打印如下：

Spring Cloud 之Ribbon负载均衡_maven_03

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) ：