zookeeper(三)---使用zookeeper实现服务的主从选举和哨兵机制

<groupId>com.junlaninfo</groupId>
<artifactId>sentry</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.0.RELEASE</version>
</parent>
<dependencies>
    <dependency>
        <groupId>com.101tec</groupId>
        <artifactId>zkclient</artifactId>
        <version>0.10</version>
        <exclusions>
            <exclusion>
                <artifactId>slf4j-api</artifactId>
                <groupId>org.slf4j</groupId>
            </exclusion>
            <exclusion>
                <artifactId>log4j</artifactId>
                <groupId>log4j</groupId>
            </exclusion>
            <exclusion>
                <artifactId>slf4j-log4j12</artifactId>
                <groupId>org.slf4j</groupId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
</dependencies>

server.port=8082

package com.junlaninfo.controller;

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

/**
 * Created by 辉 on 2020/7/4.
 */
@RestController
public class IndexController {

    @GetMapping("/getInfo")
    public  String  getInfo(){
     return  "当前是否为主节点："+Sentry.isMaster;
    }
}

package com.junlaninfo.controller;


import org.I0Itec.zkclient.IZkDataListener;
import org.I0Itec.zkclient.ZkClient;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;

/**
 * Created by 辉 on 2020/7/4.
 */
@Component
public class ZookeeperRunner implements ApplicationRunner {
    // 创建zk连接
    ZkClient zkClient = null;
    private String path = "/election";
    @Value("${server.port}")
    private String serverPort;

    @Override
    public void run(ApplicationArguments applicationArguments) throws Exception {
        System.out.println("项目已启动就执行这个方法");
        zkClient = new ZkClient("192.168.196.175:2181");
        createEphemeral();  //尝试创建节点
        //创立监听watcher，看节点有无被删除和改变
        zkClient.subscribeDataChanges(path, new IZkDataListener() {
            @Override
            public void handleDataChange(String s, Object o) throws Exception {

            }

            @Override
            public void handleDataDeleted(String s) throws Exception {
                // 主节点已经挂了，重新选举
                System.out.println("主节点已经挂了，重新开始选举");
                createEphemeral();
            }
        });
    }

    private void createEphemeral() {
        try {
            zkClient.createEphemeral(path); //创建临时节点
            Sentry.isMaster = true;         //创建节点要是成功，就把ismaster置为true，创建不成功就会出异常
        } catch (Exception e) {
            Sentry.isMaster = false;
        }


    }
}

package com.junlaninfo.controller;

import org.springframework.stereotype.Component;

/**
 * Created by 辉 on 2020/7/4.
 * 这个类主要做一个标识，看它是否为主节点
 */
@Component
public class Sentry {
    public  static  boolean isMaster;
}

package com.junlaninfo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
 * Created by 辉 on 2020/7/4.
 */
@SpringBootApplication
public class sentryApplication {
    public static void main(String[] args) {
        SpringApplication.run(sentryApplication.class);
    }
}