Eureka + Ribbon实现微服务的服务发现和负载均衡

目录

1:原理结构图

2:搭建Eureka Server服务注册中心

3：搭建Eureka Provider (服务提供者，即Eureka Client)

4：搭建 Eurka-Consumer

---

1:原理结构图

2:搭建Eureka Server服务注册中心

创建工程，引入Eureka，创建好的工程pom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.eureka</groupId>
	<artifactId>EurekaServer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

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

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.1.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>Greenwich.M3</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>

	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>


</project>

在启动类上加上 @EnableEurekaServer注解，启动注册服务中心，启动类代码如下：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

配置application.yml文件 

server:
  port: 8081 #服务注册中心端口号

eureka:
  instance:
    hostname: 127.0.0.1 #服务注册中心IP地址
  client:
    registerWithEureka: false #是否向服务注册中心注册自己
    fetchRegistry: false #是否检索服务
    serviceUrl: #服务注册中心的配置内容，指定服务注册中心的位置
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

打成jar包，运行该工程后，在浏览器上输入http://127.0.0.1:8081，看到如下界面，目前该页面暂无注册的服务提供者和消费者

3：搭建Eureka Provider (服务提供者，即Eureka Client)

创建工程，引入eureka 和spring boot web，其pom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.eureka</groupId>
	<artifactId>EurekaProvider</artifactId>
	<version>0.0.1</version>
	<packaging>jar</packaging>

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

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.1.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>Greenwich.M3</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-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>

	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>


</project>

创建一个RestController访问方法:

        @Value("${server.port}")
	private String port;
	
	@GetMapping("/home")
	public String homePage() {
		return "Welcome to home page"+" : " + port;
	}

在启动类上加上 @EnableEurekaClient注解，申明是Eureka客户端

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient

public class EurekaProviderApplication {

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

配置application.yml文件 

eureka:
  client:
    serviceUrl: #注册中心的注册地址
      defaultZone: http://127.0.0.1:8081/eureka/
server:
  port: 8082  #服务端口号
spring:
  application:
    name: service-provider #服务名称--调用的时候根据名称来调用该服务的方法

打成jar，运行两个实例

java -jar EurekaProvider-0.0.1.jar   //配置文件中设置成8082端口

java -jar EurekaProvider-0.0.1.jar --server.port=8083

成功运行后，Eureka服务注册中心会注册两个provider实例，如下界面：

4：搭建 Eurka-Consumer

主要目的是用来消费服务，同时提供负载均衡的功能。引入Eurka,web后的pom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.eureka</groupId>
	<artifactId>EurekaConsumer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

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

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.1.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>Greenwich.M3</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-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>

	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>


</project>

在启动类中往spring boot容器中添加RestTemplate对象和IRule对象(用于负载均衡)，后期会对常用的负载均衡策略方法做个总结。

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;

@SpringBootApplication
@EnableEurekaClient

public class EurekaConsumerApplication {
	
	@LoadBalanced
	@Bean
    public RestTemplate rest() {
        return new RestTemplate();
    }
	

	@Bean
	public IRule ribbonRule() {
		return new RandomRule(); //随机负载均衡策略,如未向容器中注入，默认是轮询方式
	}
	
	

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

注意：在往容器中注入RestTemplate对象时，需要加上@LoadBalanced注解，否则不能正常访问Eurka中的服务。其原理可以参考https://blog.csdn.net/jin5203344/article/details/80496078

添加Controller，提供给外部访问的接口以及访问provider提供的接口

@RestController

public class goHomePage {
	
	@Autowired
	private RestTemplate restTemplate;
	
	
	@GetMapping("/home")
	public String getHome() {
		
		String data = restTemplate.getForObject("http://service-provider/home", String.class);
		
		return data;
	
	}

}

配置application. yml

eureka:
  client:
    serviceUrl: #注册中心的注册地址
      defaultZone: http://127.0.0.1:8081/eureka/
server:
  port: 8093  #服务端口号
spring:
  application:
    name: service-consumer #服务名称--调用的时候根据名称来调用该服务的方法

运行Consumer项目，在Eureka 注册中心的管理页面上可以看到其注册信息

目前为止，已经完成 Eureka的注册中心，服务提供者，消费者。在浏览器中输入http://127.0.0.1:8093/home 即可访问到服务提供者提供的数据，如下截图：

Eureka在开发调试时会涉及到多个服务提供者，不适合点对点的调测，故后续会记录点对点的直连方式，结构如下：