05-LoadBalancer負載均衡

技術那點事兒發表於2022-03-07
負載

1、介紹

目前主流的負載方案分為以下兩種：

  • 集中式負載均衡，在消費者和服務提供方中間使用獨立的代理方式進行負載，有硬體的（比如 F5），也有軟體的（比如 Nginx）。
  • 客戶端根據自己的請求情況做負載均衡，LoadBalancer、Ribbon 就屬於客戶端自己做負載均衡。

2、快速開始

廢話不多少，上程式碼。

pom.xml

maven依賴配置檔案，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>

上面配置檔案，我們沒有新增LoadBalancer的配置，其實spring-cloud-starter-netflix-eureka-client已經依賴了一個具體實現，在老版本的是Ribbon，新的版本是Spring自己實現的loadbalancer，如下：。

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

所以不需要格外新增配置。

application.properties

服務配置檔案，也可以用yml，如下：

server.port=9003

# 服務註冊中心地址
eureka.client.service-url.defaultZone=http://localhost:9000/eureka/

# 服務名稱
spring.application.name=loadbalancer-customer

LoadBalancerConsumerApplication

服務啟動類，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 標識
@SpringBootApplication
public class LoadBalancerConsumerApplication {

	@Bean
	@LoadBalanced  		// 開啟負載均衡的功能
	RestTemplate restTemplate() {
		return new RestTemplate();
	}

	public static void main(String[] args) {
		SpringApplication.run(SpringCloudRibbonConsumerApplication.class, args);
	}
}

上面程式碼中，@LoadBalanced 註解開啟了RestTemplate的負載均衡，具體原理後面深入原始碼學習時再做了解。這裡只需要瞭解該註解標記後，該http請求會有負載均衡效果。

ConsumerController

服務呼叫，

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客戶端

	@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的話，我們只需要改一下依賴檔案即可：

<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>

這裡移出了loadbalancer ，新增Ribbon的包。其他配置不用動即可換成Ribbon

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