SpringCloud之Eureka：集群搭建

上篇文章《SpringCloud之Eureka：服务发布与调用例子》实现了一个简单例子，这次对其进行改造，运行两个服务器实例、两个服务提供者实例，服务调用者请求服务，使其可以进行集群部署。

集群结构如下图所示。

由于开发环境只有一台电脑，要构建集群，需要修改hosts文件，在里面添加主机名映射。

127.0.0.1 slave1 slave2

一、服务器端

1、创建项目

开发工具：IntelliJ IDEA 2019.2.2
IDEA中创建一个新的SpringBoot项目，名称为“first-cloud-server”，SpringBoot版本选择2.1.9，在选择Dependencies(依赖)的界面勾选Spring Cloud Discovery ->

Eureka Server，创建完成后的pom.xml配置文件自动添加SpringCloud最新稳定版本依赖，当前为Greenwich.SR3。
pom.xml完整内容可参考上篇文章《SpringCloud之Eureka：服务发布与调用例子》。

2、修改配置application.yml

由于需要对同一个应用程序启动两次，因此需要使用profiles配置。
下面配置了两个profiles，名称分别为slave1和slave2，当使用slave1启动服务器后，会向http://slave2:8762/eureka/注册自己，当使用slave2启动服务器后，会向

http://slave1:8761/eureka/注册自己，即两个服务器启动后，互相注册。

server:

  port: 8761

spring:

  application:

    name: first-cloud-server

  profiles: slave1

eureka:

  instance:

    hostname: slave1

  client:

    serviceUrl:

      defaultZone: http://slave2:8762/eureka/

---

server:

  port: 8762

spring:

  application:

    name: first-cloud-server

  profiles: slave2

eureka:

  instance:

    hostname: slave2

  client:

    serviceUrl:

      defaultZone: http://slave1:8761/eureka/

3、修改启动类代码FirstEkServerApplication.java

除了增加注解@EnableEurekaServer，还让类在启动时读取控制台输入，决定使用哪个profiles来启动服务器。

package com.example.firstcloudserver;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.boot.builder.SpringApplicationBuilder;

import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

import java.util.Scanner;

@SpringBootApplication

@EnableEurekaServer

public class FirstCloudServerApplication {

    public static void main(String[] args) {

        //SpringApplication.run(FirstCloudServerApplication.class, args);

        Scanner scan = new Scanner(System.in);

        String profiles = scan.nextLine();

        new SpringApplicationBuilder(FirstCloudServerApplication.class)

                .profiles(profiles).run(args);

    }

}

二、编写服务提供者

1、创建项目

IDEA中创建一个新的SpringBoot项目，除了名称为“first-cloud-provider”，其它步骤和上面创建服务器端一样。

2、修改配置application.yml

spring:

  application:

    name: first-cloud-provider

eureka:

  instance:

    hostname: localhost

  client:

    serviceUrl:

      defaultZone: http://localhost:8761/eureka/,http://localhost:8762/eureka/

3、添加类 User.java

package com.example.firstcloudprovider;

public class User {

    private Integer id;

    private String name;

    private String message;

    public User(Integer id, String name){

        this.id = id;

        this.name = name;

    }

    public Integer getId() {

        return id;

    }

    public void setId(Integer id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getMessage() {

        return message;

    }

    public void setMessage(String message) {

        this.message = message;

    }

}

4、添加控制器 UserController.java

package com.example.firstcloudprovider;

import org.springframework.http.MediaType;

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

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

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

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

import javax.servlet.http.HttpServletRequest;

@RestController

public class UserController {

    @RequestMapping(value = "/user/{userId}", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)

    public User findUser(@PathVariable("userId") Integer userId, HttpServletRequest request){

        User user = new User(userId, "gdjlc");

        user.setMessage(request.getRequestURL().toString());

        return user;

    }

}

5、修改启动类代码FirstCloudProviderApplication.java

除了增加注解@EnableEurekaClient，还让类在启动时读取控制台输入，决定使用哪个端口启动服务器。

package com.example.firstcloudprovider;

//import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.boot.builder.SpringApplicationBuilder;

import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

import java.util.Scanner;

@SpringBootApplication

@EnableEurekaClient

public class FirstCloudProviderApplication {

    public static void main(String[] args) {

        //SpringApplication.run(FirstCloudProviderApplication.class, args);

        Scanner scan = new Scanner(System.in);

        String port = scan.nextLine();

        new SpringApplicationBuilder(FirstCloudProviderApplication.class).properties("server.port=" + port).run(args);

    }

}

三、编写服务调用者

1、创建项目
IDEA中创建一个新的SpringBoot项目，除了名称为“first-cloud-invoker”，其它步骤和上面创建服务器端一样。

2、修改配置application.yml

server:

  port: 9000

spring:

  application:

    name: first-cloud-invoker

eureka:

  instance:

    hostname: localhost

  client:

    serviceUrl:

      defaultZone: http://slave1:8761/eureka/,http://slave2:8762/eureka/

3、添加控制器 InvokerController.java

package com.example.firstcloudinvoker;

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

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.http.MediaType;

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

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

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

import org.springframework.web.client.RestTemplate;

@RestController

@Configuration

public class InvokerController {

    @Bean

    @LoadBalanced

    public RestTemplate getRestTemplate(){

        return new RestTemplate();

    }

    @RequestMapping(value = "/router", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)

    public String router(){

        RestTemplate restTpl = getRestTemplate();

        //根据应用名称调用服务

        String json = restTpl.getForObject("http://first-cloud-provider/user/1", String.class);

        return json;

    }

}

4、修改启动类代码FirstCloudInvokerApplication.java

添加注解@EnableDiscoveryClient，使得服务调用者可以去Eureka中发现服务。

package com.example.firstcloudinvoker;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

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

@SpringBootApplication

@EnableDiscoveryClient

public class FirstCloudInvokerApplication {

    public static void main(String[] args) {

        SpringApplication.run(FirstCloudInvokerApplication.class, args);

    }

}

四、编写REST客户端进行测试

1、创建项目

IDEA中创建一个新的SpringBoot项目，名称为“first-cloud-rest-client”，SpringBoot版本选择2.1.9，在选择Dependencies(依赖)的界面勾选Web->Spring Web。
在pom.xml中增加httpclient依赖。

<?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>2.1.9.RELEASE</version>

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

    </parent>

    <groupId>com.example</groupId>

    <artifactId>first-cloud-rest-client</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>first-cloud-rest-client</name>

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

    <properties>

        <java.version>1.8</java.version>

    </properties>

    <dependencies>

        <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>

        <dependency>

            <groupId>org.apache.httpcomponents</groupId>

            <artifactId>httpclient</artifactId>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

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

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

2、修改配置application.yml

server:

  port: 9001

3、修改启动类代码FirstCloudRestClientApplication.java

编写调用REST服务的代码

package com.example.firstcloudrestclient;

import org.apache.http.HttpResponse;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.CloseableHttpClient;

import org.apache.http.impl.client.HttpClients;

import org.apache.http.util.EntityUtils;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

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

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

@SpringBootApplication

@RestController

public class FirstCloudRestClientApplication {

    public static void main(String[] args) {

        SpringApplication.run(FirstCloudRestClientApplication.class, args);

    }

    @RequestMapping("/")

    public String testHttpClient(){

        StringBuilder sb = new StringBuilder();

        try{

            CloseableHttpClient httpClient = HttpClients.createDefault();

            for(int i=0;i<10;i++){

                HttpGet httpGet = new HttpGet("http://localhost:9000/router");

                HttpResponse response = httpClient.execute(httpGet);

                sb.append(EntityUtils.toString(response.getEntity()) + "<br />");

            }

        }catch(Exception ex){

            return ex.getMessage();

        }

        return sb.toString();

    }

}

4、测试

（1）启动两个服务器端，在控制台中分别输入slave1和slave2启动。
（2）启动两个服务提供者，在控制台中分别输入8763和8764启动。
（3）启动服务调用者。
（4）启动REST客户端。

浏览器访问 http://slave1:8761/，页面如下

浏览器访问 http://slave2:8762/，页面如下

浏览器访问 http://localhost:8763/user/1，页面输出：

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

浏览器访问 http://localhost:8764/user/1，页面输出：

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

浏览器访问 http://localhost:9000/router，多次刷新页面，页面输出在8763和8764切换：

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

浏览器访问 http://localhost:9001/，页面输出

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8764/user/1"}

{"id":1,"name":"gdjlc","message":"http://localhost:8763/user/1"}

请求了10次，8763和8764分别被请求5次，可见已经达到负载均衡。

巴特西

SpringCloud之Eureka：集群搭建

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