“Hello everyone! ”
高可用的服务注册中心（Eureka）简介
SpringCloud Eureka是云端服务发现，一个基于 REST 的服务，用于定位服务，以实现云端中间层服务发现和故障转移，并且支持集群部署。
第一步：创建条件
创建一个maven主工程.
第二步：创建eureka-server工程：
右键工程->创建module->选择spring initialir->cloud discovery->eureka server,然后一直下一步就行了。
创建完成后：
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<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.test</groupId>
<artifactId>eureka-server</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>eureka-server</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.RC2</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>
</repository>
</repositories>
</project>
配置appication.yml文件：
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server:
port: 9871
spring:
profiles: peer1
application:
name: peer1
eureka:
instance:
hostname: peer1
client:
service-url:
defaultZone: http://peer2:9872/eureka/
第三步 配置主程序
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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);
}
}
第四步：创建eureka-server2工程：
选择配置包不变，配置appication.yml文件：
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server:
port: 9872
spring:
profiles: peer2
application:
name: peer2
eureka:
instance:
hostname: peer2
client:
service-url:
defaultZone: http://peer1:9871/eureka/
第五步：创建eureka-client工程：
右键工程->创建module->选择spring initialir->cloud discovery->eureka client,然后一直下一步就行了。
创建完成后：
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<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.test</groupId>
<artifactId>eureka-client</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>eureka-client</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.RC2</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-client</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>
</repository>
</repositories>
</project>
配置appication.yml文件：
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server:
port: 9873
spring:
application:
name: eureka-client
eureka:
client:
service-url:
defaultZone: http://peer1:9871/eureka/
第六步 配置主程序
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import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@SpringBootApplication
@EnableEurekaClient
@RestController
public class EurekaClientApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaClientApplication.class, args);
}
@RequestMapping("hello")
public String hello(@RequestParam String name){
return "hello, " + name;
}
}
第七步 启动程序
配置Configurations
EurekaServerApplication的Program arguments：
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--spring.profiles.active=peer1
EurekaServer2Application的Program arguments：
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--spring.profiles.active=peer2
启动eureka-server，eureka-server2,eureka-client
访问：localhost:9871，你会发现注册了eureka-client，并且有个peer2节点，同理访问localhost:9872你会发现有个peer1节点。 client只向9871注册，但是你打开9872，你也会发现，9872也有 client的注册信息。
访问：http://localhost:9873/hello?name=handsomeman，浏览器出现：
hello, handsomeman
然后随便关闭一台server，
同理，访问：http://localhost:9873/hello?name=handsomeman，浏览器出现：
hello, handsomeman
Eureka-eserver peer1 9871,Eureka-eserver peer2 9872相互感应，当有服务注册时，两个Eureka-eserver是对等的， 它们都存有相同的信息，这就是通过服务器的冗余来增加可靠性，当有一台服务器宕机了，服务并不会终止， 因为另一台服务存有相同的数据。
源码下载：
https://github.com/mochengyanliu/SpringCloudLearn/tree/master/section10
