SpringCloud从入门到精通——Eureka服务注册中心

悠悠 2023-09-29 11:19 27阅读 0赞

## Eureka服务注册中心 ##

#### 目录 ####

*  Eureka服务注册中心
 *   *  1. Eureka基本介绍
     *  2. Eureka环境构建
     *   *  2.1 EurekaServer端
         *   *  2.1.1 Maven依赖
             *  2.1.2 配置文件
             *  2.1.3 启动类
         *  2.2 EurekaClient端
         *   *  2.2.1 Maven
             *  2.2.2 配置文件
             *  2.2.3 启动类
         *  2.3 服务发现
         *   *  2.3.1 Maven
             *  2.3.2 配置文件
             *  2.3.3 启动类
             *  2.2.4 接口
             *  2.2.5 工具类
         *  2.4 Eureka 常用配置解析
     *  3. 效果展示
     *   *  3.1 启动EurekaServer端
         *  3.2 启动EurekaClient端
         *  3.3 启动服务发现
         *  3.4 接口测试

### 1. Eureka基本介绍 ###

**Eureka是Netflix开发的服务发现框架，本身是一个基于REST的服务，主要用于定位运行在AWS域中的中间层服务，以达到负载均衡和中间层服务故障转移的目的。**  
SpringCloud将它集成在其子项目spring-cloud-netflix中，以实现SpringCloud的服务发现功能。

Eureka包含两个组件：**Eureka Server和Eureka Client**。  
Eureka Server提供服务注册服务，各个节点启动后，会在Eureka Server中进行注册，这样EurekaServer中的服务注册表中将会存储所有可用服务节点的信息，服务节点的信息可以在界面中直观的看到。  
Eureka Client是一个java客户端，用于简化与Eureka Server的交互，客户端同时也就是一个内置的、使用轮询(round-robin)负载算法的负载均衡器。

在应用启动后，将会向Eureka Server发送心跳,默认周期为30秒，如果Eureka Server在多个心跳周期内没有接收到某个节点的心跳，Eureka Server将会从服务注册表中把这个服务节点移除(默认90秒)。  
Eureka Server之间通过复制的方式完成数据的同步，Eureka还提供了客户端缓存机制，即使所有的Eureka Server都挂掉，客户端依然可以利用缓存中的信息消费其他服务的API。**综上，Eureka通过心跳检查、客户端缓存等机制，确保了系统的高可用性、灵活性和可伸缩性。**

### 2. Eureka环境构建 ###

#### 2.1 EurekaServer端 ####

##### 2.1.1 Maven依赖 #####

<dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            </dependency>
        </dependencies>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Finchley.RC2</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>

##### 2.1.2 配置文件 #####

server:
      port: 9090 #服务注册中心端口号
    spring:
      application:
        name: spring-cloud-eureka-server
    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/

##### 2.1.3 启动类 #####

package com.demo;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
    
    /**
     * @Author: JYC
     * @Title: AppEurekaServer
     * @Description: TODO
     * @Date: 2022/4/21 18:46
     */
    @SpringBootApplication
    @EnableEurekaServer
    public class AppEurekaServer {
        
        public static void main(String[] args) {
        
            SpringApplication.run(AppEurekaServer.class);
        }
    }

#### 2.2 EurekaClient端 ####

##### 2.2.1 Maven #####

<dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
        </dependencies>
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Finchley.RC2</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>

##### 2.2.2 配置文件 #####

server:
      port: 8080
    spring:
      application:
        name: demo-member   #服务名称 在注册中心展示服务名称
    eureka:
      client:
        service-url: # 服务注册中心地址
          defaultZone: http://127.0.0.1:9090/eureka/

##### 2.2.3 启动类 #####

package com.demo.service;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    
    /**
     * @Author: JYC
     * @Title: com.demo.service.AppMember
     * @Description: TODO
     * @Date: 2022/4/21 13:59
     */
    @SpringBootApplication
    @EnableEurekaClient
    public class AppMember {
        
        public static void main(String[] args) {
        
            SpringApplication.run(AppMember.class);
        }
    }

#### 2.3 服务发现 ####

##### 2.3.1 Maven #####

<dependencies>
            <dependency>
                <groupId>org.apache.httpcomponents</groupId>
                <artifactId>httpclient</artifactId>
                <version>4.5.5</version>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
        </dependencies>
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Finchley.RC2</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <repositories>
            <repository>
                <id>spring-milestones</id>
                <name>Spring Milestones</name>
                <url>https://repo.spring.io/milestone</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
            </repository>
        </repositories>

##### 2.3.2 配置文件 #####

server:
      port: 8070
    spring:
      application:
        name: demo-order   #服务名称 在注册中心展示服务名称
    eureka:
      client:
        service-url: # 服务注册中心地址
          defaultZone: http://127.0.0.1:9090/eureka/

##### 2.3.3 启动类 #####

package com.demo;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    
    /**
     * @Author: JYC
     * @Title: AppOrder
     * @Description: TODO
     * @Date: 2022/4/21 14:10
     */
    @SpringBootApplication
    @EnableDiscoveryClient
    public class AppOrder {
        
        public static void main(String[] args) {
        
            SpringApplication.run(AppOrder.class);
        }
    }

##### 2.2.4 接口 #####

package com.demo.service;
    
    import com.demo.utils.HttpClientUtils;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.client.discovery.DiscoveryClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import java.util.List;
    
    /**
     * @Author: JYC
     * @Title: OrderToMemberService
     * @Description: TODO
     * @Date: 2022/4/21 14:04
     */
    @RestController
    public class OrderToMemberService {
        
        @Autowired
        private DiscoveryClient discoveryClient;
    
        /**
         * 订单服务，调用 会员服务接口
         */
        @RequestMapping("/orderToMember")
        public String OrderToMember() {
        
            // HttpClient 工具类 实现RPC远程调用
    //        String memberUrl = "http://192.168.66.1:8080/getMember";
            /**
             * 根据服务名称，从注册中心获取会员的接口地址
             */
            List<ServiceInstance> instances = discoveryClient.getInstances("demo-member");
            ServiceInstance serviceInstance = instances.get(0);
            // 会员服务的ip和端口
            String memberUrl = "http://" + serviceInstance.getHost() + ":" + serviceInstance.getPort() + "/" + "getMember";
            return "订单服务调用会员服务：" + HttpClientUtils.doGet(memberUrl, null);
        }
    }

##### 2.2.5 工具类 #####

package com.demo.utils;
    
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.http.HttpEntity;
    import org.apache.http.NameValuePair;
    import org.apache.http.ParseException;
    import org.apache.http.client.config.RequestConfig;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.CloseableHttpResponse;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.HttpClientBuilder;
    import org.apache.http.message.BasicNameValuePair;
    import org.apache.http.util.EntityUtils;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    
    /**
     * @Author: JYC
     * @Title: OrderToMemberService
     * @Description: TODO
     * @Date: 2022/4/21 14:04
     */
    
    public class HttpClientUtils {
        
    
        private static final CloseableHttpClient httpClient;
        public static final String CHARSET = "UTF-8";
        private static final Log log = LogFactory.getLog(HttpClientUtils.class);
    
        // 采用静态代码块，初始化超时时间配置，再根据配置生成默认httpClient对象
        static {
        
            RequestConfig config = RequestConfig.custom().setConnectTimeout(60000).setSocketTimeout(15000).build();
            httpClient = HttpClientBuilder.create().setDefaultRequestConfig(config).build();
        }
    
        public static String doGet(String url, Map<String, String> params) {
        
            return doGet(url, params, CHARSET);
        }
    
    
        public static String doPost(String url, Map<String, String> params) throws IOException {
        
            return doPost(url, params, CHARSET);
        }
    
        /**
         * HTTP Get 获取内容
         *
         * @param url     请求的url地址 ?之前的地址
         * @param params  请求的参数
         * @param charset 编码格式
         * @return 页面内容
         */
        public static String doGet(String url, Map<String, String> params, String charset) {
        
            try {
        
                if (params != null && !params.isEmpty()) {
        
                    List<NameValuePair> pairs = new ArrayList<NameValuePair>(params.size());
                    for (Map.Entry<String, String> entry : params.entrySet()) {
        
                        String value = entry.getValue();
                        if (value != null) {
        
                            pairs.add(new BasicNameValuePair(entry.getKey(), value));
                        }
                    }
                    // 将请求参数和url进行拼接
                    url += "?" + EntityUtils.toString(new UrlEncodedFormEntity(pairs, charset));
                }
                HttpGet httpGet = new HttpGet(url);
                CloseableHttpResponse response = httpClient.execute(httpGet);
                int statusCode = response.getStatusLine().getStatusCode();
                if (statusCode != 200) {
        
                    httpGet.abort();
                    throw new RuntimeException("HttpClient,error status code :" + statusCode);
                }
                HttpEntity entity = response.getEntity();
                String result = null;
                if (entity != null) {
        
                    result = EntityUtils.toString(entity, "utf-8");
                }
                EntityUtils.consume(entity);
                response.close();
                return result;
            } catch (Exception e) {
        
                log.error("请求服务器端出错:" + e);
                return null;
            }
    
        }
    
        /**
         * HTTP Post 获取内容
         *
         * @param url     请求的url地址 ?之前的地址
         * @param params  请求的参数
         * @param charset 编码格式
         * @return 页面内容
         * @throws IOException
         */
        public static String doPost(String url, Map<String, String> params, String charset)
                throws IOException {
        
            List<NameValuePair> pairs = null;
            if (params != null && !params.isEmpty()) {
        
                pairs = new ArrayList<NameValuePair>(params.size());
                for (Map.Entry<String, String> entry : params.entrySet()) {
        
                    String value = entry.getValue();
                    if (value != null) {
        
                        pairs.add(new BasicNameValuePair(entry.getKey(), value));
                    }
                }
            }
            HttpPost httpPost = new HttpPost(url);
            if (pairs != null && pairs.size() > 0) {
        
                httpPost.setEntity(new UrlEncodedFormEntity(pairs, CHARSET));
            }
            CloseableHttpResponse response = null;
            try {
        
                response = httpClient.execute(httpPost);
                int statusCode = response.getStatusLine().getStatusCode();
                if (statusCode != 200) {
        
                    httpPost.abort();
                    throw new RuntimeException("HttpClient,error status code :" + statusCode);
                }
                HttpEntity entity = response.getEntity();
                String result = null;
                if (entity != null) {
        
                    result = EntityUtils.toString(entity, "utf-8");
                }
                EntityUtils.consume(entity);
                return result;
            } catch (ParseException e) {
        
                log.error("请求服务器端出错:" + e);
                return null;
            } finally {
        
                if (response != null)
                    response.close();
            }
        }
    }

#### 2.4 Eureka 常用配置解析 ####

> Eureka 常用配置解析[（点击跳转）][Link 1]

### 3. 效果展示 ###

#### 3.1 启动EurekaServer端 ####

![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bC85Y-k5ouJ5pav54uX6JuL5YS_size_20_color_FFFFFF_t_70_g_se_x_16]  
浏览器访问：http://127.0.0.1:9090/  
`出现如下界面表示服务端启动成功`  
![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bC85Y-k5ouJ5pav54uX6JuL5YS_size_20_color_FFFFFF_t_70_g_se_x_16 1]

#### 3.2 启动EurekaClient端 ####

![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bC85Y-k5ouJ5pav54uX6JuL5YS_size_20_color_FFFFFF_t_70_g_se_x_16 2]  
浏览器访问：http://127.0.0.1:9090/  
`在界面中能看到"DEMO-MEMBER"表示启动成功`  
![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bC85Y-k5ouJ5pav54uX6JuL5YS_size_20_color_FFFFFF_t_70_g_se_x_16 3]

#### 3.3 启动服务发现 ####

![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bC85Y-k5ouJ5pav54uX6JuL5YS_size_20_color_FFFFFF_t_70_g_se_x_16 4]  
浏览器访问：http://127.0.0.1:9090/  
`在界面中能看到"DEMO-ORDER"表示启动成功`  
![在这里插入图片描述][watermark_type_d3F5LXplbmhlaQ_shadow_50_text_Q1NETiBA5bC85Y-k5ouJ5pav54uX6JuL5YS_size_20_color_FFFFFF_t_70_g_se_x_16 5]

#### 3.4 接口测试 ####

在浏览器中输入：http://127.0.0.1:8070/orderToMember  
![在这里插入图片描述][b0045d273a3a43e0a13249a2487df3bd.png]

[Link 1]: https://blog.csdn.net/qq_30999361/article/details/124334087
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[b0045d273a3a43e0a13249a2487df3bd.png]: https://img-blog.csdnimg.cn/b0045d273a3a43e0a13249a2487df3bd.png