Spring-Cloud-Finchley | 负载均衡 RestTemplate+Ribbon

简介

负载均衡提供了一种廉价的方式扩展网络设备和服务器带宽，增加吞吐量，加强网络数据的处理能力，也就是把多个请求分摊到不同的服务器上，降低单台服务器的压力。

Ribbon 和 Nginx 都可以用来做负载均衡，他们的区别与场景如下：

Nginx 是服务器负载均衡，Ribbon 是客户端负载均衡，Nginx 是客户端把所有请求交给 Nginx，由 Nginx 进行转发，Ribbon 是从注册中心获取注册信息，缓存到本地，然后在本地实现负载均衡策略。

Nginx 通常在服务器端实现负载均能，比如 Tomcat，Ribbon 则使用在微服务中的 RPC 调用实现负载均衡。

实例

1、创建 maven 工程

创建 maven 工程，添加核心的父 maven 依赖，所有子 pom 文件继承这个父 pom 文件。

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
  </properties>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.5.RELEASE</version>
    <relativePath/>
  </parent>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </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>

2、搭建注册中心 eureka-server

添加 maven 依赖

<parent>
		<groupId>com.hly</groupId>
		<artifactId>02-spring-cloud-rest-ribbon</artifactId>
		<version>1.0-SNAPSHOT</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>
	</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-web</artifactId>
		</dependency>
	</dependencies>

application.yml 配置

server:
  port: 8761

eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

spring:
  application:
    name: eureka-server

SpringBoot 启动类

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

3、搭建服务提供者 eureka-client

添加 maven 依赖

	<groupId>com.hly</groupId>
	<artifactId>eureka-client</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>eureka-client</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>com.hly</groupId>
		<artifactId>02-spring-cloud-rest-ribbon</artifactId>
		<version>1.0-SNAPSHOT</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>
	</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>
	</dependencies>

application.yml 配置

server:
  port: 8763

spring:
  application:
    name: eureka-client

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

SpringBoot 启动类

@SpringBootApplication
@RestController
@EnableEurekaClient
public class EurekaClientApplication {

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

	@Value("${server.port}")
	String port;

	@RequestMapping("/hello")
	public String home(@RequestParam(value = "name", defaultValue = "hly") String name) {
		return "hi " + name + " ,i am from port:" + port;
	}
}

4、搭建服务消费者 eureka-client-ribbon

添加 maven 依赖

	<parent>
		<groupId>com.hly</groupId>
		<artifactId>02-spring-cloud-rest-ribbon</artifactId>
		<version>1.0-SNAPSHOT</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>
	</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.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
		</dependency>

application.yml 配置

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8764
spring:
  application:
    name: eureka--ribbon

SpringBoot 启动类

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
public class EurekaClientRibbonApplication {

	public static void main(String[] args) {
		SpringApplication.run(EurekaClientRibbonApplication.class, args);
	}
	@Bean
	//表明这个restRemplate开启负载均衡的功能
	@LoadBalanced
	RestTemplate restTemplate() {
		return new RestTemplate();
	}
}

服务层类

@Service
public class HelloService {

    @Autowired
    RestTemplate restTemplate;

    public String hiService(String name) {
        //调用该方法，做了负载均衡，访问不同端口的实例
        return restTemplate.getForObject("http://EUREKA-CLIENT/hello?name="+name,String.class);
    }

    /**
     * 启动两个服务，关闭一个，只能访问另一个，两个都关闭，将输出以下错误语句
     * @param name
     * @return
     */
    public String helloError(String name){
        return "hello,"+name+",sorry,error";
    }
}

Controller 层类，消费服务提供者

@RestController
public class HelloController {

    @Autowired
    HelloService helloService;

    /**
     * 启动多个集群，浏览器多次访问 http://localhost:8764/hi?name=hly，交替出现结果
     * @param name
     * @return
     */
    @GetMapping(value = "/hi")
    public String hi(@RequestParam String name) {
        return helloService.hiService(name);
    }
}

演示

1、依次启动 注册中心 eureka-server ，启动两个 eureka-client(启动一个后，修改application.yml 配置文件的端口，再次启动一次)，启动服务消费者 eureka-client-ribbon
2、浏览器访问 http://localhost:8764/hi?name=hly ，然后刷新浏览器，会交替调用两个客户端，实现了两个客户端的负载均衡。

思维导图

Ribbon 使用示例思维导图

代码下载

02-spring-cloud-rest-ribbon：https://github.com/huangliangyun/Spring-Cloud-Finchley

关于

我的 Github：Github
CSDN: CSDN
个人网站: sirius 的博客
E-mail: [email protected]

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