前言

spring-cloud为基础的微服务架构，所有的微服务都需要注册到注册中心，如果这个注册中心阻塞或者崩了，那么整个系统都无法继续正常提供服务，所以，这里就需要对注册中心进行集群，换言之，高可用（HA）

一、在本地布署的机器上修改hosts文件

这个案例中主要实现两个注册中心的集群。所以在hosts中加上两个解析。
在hosts加上

127.0.0.1       eureka-server1
127.0.0.1       eureka-server2

如下修改

mac下修改:

sudo vim /etc/hosts

image.png

windows下修改
C:\Windows\System32\drivers\etc\hosts
用记事本打开在后面加上
127.0.0.1 eureka-server1
127.0.0.1 eureka-server2

二、这里用idea演示创建项目。

集群中项目代码都是一样的。只是配制文件不一样。

1.步骤一

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2.步骤二

image.png

3.步骤三

image.png

4.步骤四

image.png

5.步骤五

image.png

三、实现Eureka项目代码.

项目结构

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1、pom.xml文件

<?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.joychen</groupId>
    <artifactId>eurekajuqun</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>eurekajuqun</name>
    <description>eureka ju qun</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.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>Finchley.M8</spring-cloud.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.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>${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>


</project>

2、EurekajuqunApplication.java启动项目文件

image.png

package com.joychen.eurekajuqun;

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

@SpringBootApplication
@EnableEurekaServer
public class EurekajuqunApplication {

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

3、三个监听文件之1
1.心跳检测注册中心是否挂了

image.png

package com.joychen.eurekajuqun.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.netflix.eureka.server.event.EurekaInstanceRenewedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;

/**
 * joychen
 */
@Configuration
public class InstanceRenewListener implements ApplicationListener<EurekaInstanceRenewedEvent> {
    private static final Logger LOGGER = LoggerFactory.getLogger(InstanceRenewListener.class);
    @Override
    public void onApplicationEvent(EurekaInstanceRenewedEvent event) {
        LOGGER.info("心跳检测服务：{}serverid="+event.getServerId() ,event.getInstanceInfo().getAppName());
    }
}

4、三个监听文件之2
2.监控是否有服务注册过来

image.png

package com.joychen.eurekajuqun.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.netflix.eureka.server.event.EurekaInstanceRegisteredEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;

/**
 * joychen
 */
@Configuration
public class InstanceRegisterListener implements ApplicationListener<EurekaInstanceRegisteredEvent>{
    private static final Logger LOGGER = LoggerFactory.getLogger(InstanceRegisterListener.class);
    @Override
    public void onApplicationEvent(EurekaInstanceRegisteredEvent eurekaInstanceRegisteredEvent) {
        LOGGER.info("服务：，注册成功了appname="+eurekaInstanceRegisteredEvent.getInstanceInfo().getAppName(),eurekaInstanceRegisteredEvent.getInstanceInfo().getAppName());
    }
}

5、三个监听文件之3
3.监控是否有服务挂了

image.png

package com.joychen.eurekajuqun.listener;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.netflix.eureka.server.event.EurekaInstanceCanceledEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.Configuration;

/**
 * joychen
 */
@Configuration
public class InstanceCancelListener implements ApplicationListener<EurekaInstanceCanceledEvent> {
    private static final Logger LOGGER = LoggerFactory.getLogger(InstanceCancelListener.class);
    @Override
    public void onApplicationEvent(EurekaInstanceCanceledEvent event) {
        LOGGER.info("服务:挂了serverid:"+event.getServerId(),event.getAppName());
    }
}

6、配制文件
这里有三个配制文件：

image.png
第一个applicaiotn.yml
用java启动 jar 时，不带任何参数时调用这个

server:
  port: 9010
spring:
  application:
    name: eureka-server
eureka:
  instance:
    hostname: eureka-server1
  client:
    register-with-eureka: false
    fetch-registry: false
    service-url:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
  server:
  #### 清理间隔（单位毫秒，默认是60*1000），开发环境设置如下可快速移除不可用的服务
    eviction-interval-timer-in-ms: 5000
    enable-self-preservation: false

第二个applicaiotn-server1.yml
用java启动 jar 时，带参数如下行进会调用这个文件
java -Xmx1024m -Xms1024m -jar target/eurekajuqun-0.0.1-SNAPSHOT.jar --spring.profiles.active=server1

server:
  port: 9010
spring:
  application:
   ##name必须一样，不然高可用会导致unavailable-replicas
    name: eureka-server
eureka:
  instance:
    hostname: eureka-server1
  client:
    ##这里要覆盖application的设置，不然会读取application文件导致unavailable-replicas
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://eureka-server2:9011/eureka/

第三个applicaiotn-server2.yml
用java启动 jar 时，带参数如下行进会调用这个文件
java -Xmx1024m -Xms1024m -jar target/eurekajuqun-0.0.1-SNAPSHOT.jar --spring.profiles.active=server2

server:
  port: 9011
spring:
  application:
   ##name必须一样，不然高可用会导致unavailable-replicas
    name: eureka-server
eureka:
  instance:
    hostname: eureka-server2
  client:
    ##这里要覆盖application的设置，不然会读取application文件导致unavailable-replicas
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://eureka-server1:9010/eureka/

到这整个项目就完了。

对于启动项目，如果在linux跟mac我写了两个启动文件

image.png

把两个文件给上执行权限：

 apple$ sudo chmod +x *.sh

执行

./server1.sh 
./server2.sh 

最后上代码：
链接:https://pan.baidu.com/s/1_QLZRPhEKpq-PDVlsWgj3A 密码:3b0w