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引言

Eureka是Netflix开源的一款服务发现框架，它主要用于在微服务架构中定位服务，是服务之间调用的枢纽和关键。在微服务架构中，服务实例可能会动态地增加或减少，Eureka提供了服务注册和发现的功能，使得服务实例可以相互发现对方，而不需要硬编码服务地址。

Eureka的两个主要组件：
Eureka Server：服务注册中心，用于维护各个微服务实例的注册信息，各个微服务实例在启动时会向Eureka Server注册自己的信息，并定期发送心跳以表明自己的存活状态。当服务实例关闭或者网络问题导致心跳丢失时，Eureka Server会从注册信息中移除该实例。

Eureka Client：服务提供者和消费者都会使用Eureka Client来与Eureka Server进行通信。服务提供者在启动时会向Eureka Server注册自己的服务地址和端口，服务消费者通过Eureka Server查询服务提供者的地址，然后直接调用。

Eureka是Spring Cloud体系中的核心组件之一，它与Spring Cloud的其他组件（如Ribbon、Feign、Hystrix等）协同工作，提供了一套完整的微服务解决方案。通过Eureka，开发者可以更容易地实现服务的注册与发现，从而构建和管理复杂的微服务系统。

1. 搭建Eureka Server

1.1. 添加Eureka Server依赖

新建立springboot工程，添加Eureka Server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>2.0.7.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.example</groupId><artifactId>eurakaservertrue</artifactId><version>0.0.1-SNAPSHOT</version><name>eurakaservertrue</name><description>Demo project for Spring Boot</description><url/><licenses><license/></licenses><developers><developer/></developers><scm><connection/><developerConnection/><tag/><url/></scm><properties><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</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.junit.jupiter</groupId><artifactId>junit-jupiter</artifactId><version>RELEASE</version><scope>test</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Finchley.SR2</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></project>

1.2. 添加 Eureka Server注解

在启动类上添加注解，表明为Eureka Server
@EnableEurekaServer

1.3. 配置Eureka Server

spring.application.name=eurakaservertrue
server.port=8761
#从注册表中获取信息
eureka.client.fetch-registry=false
#允许自己注册到服务中
eureka.client.register-with-eureka=false

1.4. 运行Eureka Server

访问http://localhost:8761/ 出现此界面表示已经搭建好了服务

2. 搭建Eureka Client 服务提供者

2.1. 添加依赖

新建立一个spirngboot工程，并添加Eureka Client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>2.0.7.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.example</groupId><artifactId>erakaclientprovide</artifactId><version>0.0.1-SNAPSHOT</version><name>erakaclientprovide</name><description>Demo project for Spring Boot</description><url/><licenses><license/></licenses><developers><developer/></developers><scm><connection/><developerConnection/><tag/><url/></scm><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><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.junit.jupiter</groupId><artifactId>junit-jupiter</artifactId><version>RELEASE</version><scope>test</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Finchley.SR2</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></project>

2.2. 添加注解

@EnableDiscoveryClient

2.3. 配置Eureka Client

spring.application.name=erakaclientprovide
server.port=8081eureka.client.service-url.defaultZone: http://localhost:8761/eureka/
#自定义实例ID
eureka.instance.instance-id=${spring.application.name}:${spring.cloud.client.ip-address}：${server.port}

2.4. 启动服务

3. 搭建Eureka Client 消费者

3.1. 添加依赖

<?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>2.0.7.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.example</groupId><artifactId>erakaclientconsumer</artifactId><version>0.0.1-SNAPSHOT</version><name>erakaclientconsumer</name><description>Demo project for Spring Boot</description><url/><licenses><license/></licenses><developers><developer/></developers><scm><connection/><developerConnection/><tag/><url/></scm><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><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.junit.jupiter</groupId><artifactId>junit-jupiter</artifactId><version>RELEASE</version><scope>test</scope></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Finchley.SR2</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></project>

3.2. 配置

spring.application.name=erakaclientconsumer
server.port=8082eureka.client.service-url.defaultZone: http://localhost:8761/eureka/
#自定义实例ID
eureka.instance.instance-id=${spring.application.name}:${spring.cloud.client.ip-address}：${server.port}

3.3. 服务消费者获取服务提供者信息

编写controller 方法获取

package com.example.erakaclientconsumer.controller;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.GetMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.List;
import java.util.stream.Collectors;/*** @Auther： lifang* @Description* @Date: $ $* $* $**/
@RestController
public class EurekeController {@Autowiredprivate DiscoveryClient discoveryClient;//获取Eureka服务中所有的提供者信息@GetMapping("/instance")public List<ServiceInstance> getApplication(){List<ServiceInstance> instances=discoveryClient.getServices().stream().map(sid->discoveryClient.getInstances(sid)).collect(Collectors.toList()).stream().flatMap(list->list.stream()).collect(Collectors.toList());return instances;}
}

3.4. 启动服务消费者

访问 http://localhost:8761/

访问 http://localhost:8082/instance

[{"metadata": {"management.port": "8082"},"secure": false,"uri": "http://localhost:8082","instanceInfo": {"instanceId": "erakaclientconsumer:192.168.10.1��8082","app": "ERAKACLIENTCONSUMER","appGroupName": null,"ipAddr": "192.168.10.1","sid": "na","homePageUrl": "http://localhost:8082/","statusPageUrl": "http://localhost:8082/actuator/info","healthCheckUrl": "http://localhost:8082/actuator/health","secureHealthCheckUrl": null,"vipAddress": "erakaclientconsumer","secureVipAddress": "erakaclientconsumer","countryId": 1,"dataCenterInfo": {"@class": "com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo","name": "MyOwn"},"hostName": "localhost","status": "UP","overriddenStatus": "UNKNOWN","leaseInfo": {"renewalIntervalInSecs": 30,"durationInSecs": 90,"registrationTimestamp": 1731075179095,"lastRenewalTimestamp": 1731075329123,"evictionTimestamp": 0,"serviceUpTimestamp": 1731075179095},"isCoordinatingDiscoveryServer": false,"metadata": {"management.port": "8082"},"lastUpdatedTimestamp": 1731075179095,"lastDirtyTimestamp": 1731075179034,"actionType": "ADDED","asgName": null},]

4 搭建集群

集群多个节点组成的服务器群，一个Eureka Server服务是一个节点，不同节点之间服务信息是相互复制的，对于Eureka Server不同的节点代码是一样的，不同的是地址不同，因此我们通过配置不同环境的方法启动2个Eureka Server，创建 application-A.properties 和application-B.properties，在application.properties,指定当前的配置文件，启动后更改下一个节点的配置文件；

server.port=8762
eureka.client.service-url.defaultZone: http://localhost:8761/eureka/

server.port=8761
eureka.client.service-url.defaultZone: http://localhost:8762/eureka/

spring.profiles.active=B