1、介绍

目前主流的负载方案分为以下两种：

集中式负载均衡，在消费者和服务提供方中间使用独立的代理方式进行负载，有硬件的（比如 F5），也有软件的（比如 Nginx）。
客户端根据自己的请求情况做负载均衡，LoadBalancer、Ribbon 就属于客户端自己做负载均衡。

2、快速开始

废话不多少，上代码。

pom.xml

maven依赖配置文件，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 http://maven.apache.org/xsd/maven-4.0.0.xsd">

	<modelVersion>4.0.0</modelVersion>

	<groupId>com.mindasoft</groupId>

	<artifactId>spring-cloud-ribbon-consumer</artifactId>

	<version>0.0.1-SNAPSHOT</version>

	<packaging>jar</packaging>

	<name>spring-cloud-ribbon-consumer</name>

	<description>Demo project for Spring Boot</description>

	<parent>

		<groupId>org.springframework.boot</groupId>

		<artifactId>spring-boot-starter-parent</artifactId>

		<version>2.6.4</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>2021.0.1</spring-cloud.version>

	</properties>

	<dependencies>

		<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-web</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>

	<repositories>

		<repository>

			<id>nexus-aliyun</id>

			<name>Nexus aliyun</name>

			<url>https://maven.aliyun.com/repository/public</url>

			<layout>default</layout>

			<snapshots>

				<enabled>false</enabled>

			</snapshots>

			<releases>

				<enabled>true</enabled>

			</releases>

		</repository>

	</repositories>

	<pluginRepositories>

		<pluginRepository>

			<id>nexus-aliyun</id>

			<name>Nexus aliyun</name>

			<url>https://maven.aliyun.com/repository/public</url>

			<snapshots>

				<enabled>false</enabled>

			</snapshots>

			<releases>

				<enabled>true</enabled>

			</releases>

		</pluginRepository>

	</pluginRepositories>

</project>

上面配置文件，我们没有新增LoadBalancer的配置，其实spring-cloud-starter-netflix-eureka-client已经依赖了一个具体实现，在老版本的是Ribbon，新的版本是Spring自己实现的loadbalancer，如下：。

<dependency>

    <groupId>org.springframework.cloud</groupId>

    <artifactId>spring-cloud-starter-loadbalancer</artifactId>

</dependency>

所以不需要格外添加配置。

application.properties

服务配置文件，也可以用yml，如下：

server.port=9003

# 服务注册中心地址

eureka.client.service-url.defaultZone=http://localhost:9000/eureka/

# 服务名称

spring.application.name=loadbalancer-customer

LoadBalancerConsumerApplication

服务启动类，如下：

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;

import org.springframework.context.annotation.Bean;

import org.springframework.web.client.RestTemplate;

@EnableDiscoveryClient // Eureka Discovery Client 标识

@SpringBootApplication

public class LoadBalancerConsumerApplication {

	@Bean

	@LoadBalanced  		// 开启负载均衡的功能

	RestTemplate restTemplate() {

		return new RestTemplate();

	}

	public static void main(String[] args) {

		SpringApplication.run(SpringCloudRibbonConsumerApplication.class, args);

	}

}

上面代码中，@LoadBalanced 注解开启了RestTemplate的负载均衡，具体原理后面深入源码学习时再做了解。这里只需要了解该注解标记后，该http请求会有负载均衡效果。

ConsumerController

服务调用，

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.client.RestTemplate;

/**

 * Created by huangmin

 */

@RestController

public class ConsumerController {

	private static final Logger LOGGER = LoggerFactory.getLogger(ConsumerController.class);

	@Autowired

	private RestTemplate restTemplate; // HTTP客户端

	@RequestMapping("/hello")

	public String hello() {

		String providerMsg = restTemplate.getForEntity("http://PROVIDER-SERVICE/hello",

				String.class).getBody();

		return "Hello,I'm Customer! msg from provider : <br/><br/> " + providerMsg;

	}

}

3、Ribbon

如果需要使用Ribbon的话，我们只需要改一下依赖文件即可：

<dependencies>

	<dependency>

		<groupId>org.springframework.cloud</groupId>

		<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>

		<exclusions>

			<exclusion>

				<groupId>org.springframework.cloud</groupId>

				<artifactId>spring-cloud-loadbalancer</artifactId>

			</exclusion>

		</exclusions>

	</dependency>

	<dependency>

		<groupId>org.springframework.cloud</groupId>

		<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>

                <version>2.2.10.RELEASE</version>

	</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>

		<scope>test</scope>

	</dependency>

</dependencies>

这里移出了loadbalancer ，添加Ribbon的包。其他配置不用动即可换成Ribbon

巴特西

05-LoadBalancer负载均衡