简介

最近做的项目用的是zookeeper+kafka，大致学习了下zookeeper。像Spring有IOC和AOP一样，zookeeper的核心主要是文件结构和监听机制

安装

Zookeeper 的安装还是比较简单的，注意安装目录不要有中文和空格即可，本文用的版本是3.4.6

启动

Windows系统双击zkServer.cmd启动

启动闪退的话，右键编辑zkServer.cmd，在末尾加上pause

保存后继续双击运行，一般会有报错产生，没有报错说明正常启动

提示找不到配置文件，需要在config中修改配置文件

将zoo_sample.cfg文件复制一份重命名为zoo.cfg，右键编辑

这样双击zkServer.cmd就可以正常启动了

常用操作

双击zkCli.cmd启动客户端

1.ls 查看指定路径下的节点

2.create：创建一个节点

创建内容为test的/newnode节点

3.get：显示指定路径下节点的信息

4.set：设置节点的内容

可以和get的节点对比看下

5.delete：删除一个节点

java案例

熟悉了zookeeper的常用操作后，我们基于zookeeper的文件结构和监听机制来用java模拟下服务节点的动态上下线。熟悉SpringCloud的小伙伴可能清楚，我们微服务架构下的EurekaService会在单独服务启动成功后，自动在注册中心显示，服务下线后会自动在注册中心下线，下面代码就是模拟了这种服务的发现与注销

<!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->

<dependency>

<groupId>org.apache.zookeeper</groupId>

<artifactId>zookeeper</artifactId>

<version>3.4.6</version>

<type>pom</type>

</dependency>

服务端

import org.apache.zookeeper.KeeperException;

import org.apache.zookeeper.WatchedEvent;

import org.apache.zookeeper.Watcher;

import org.apache.zookeeper.ZooKeeper;

import java.util.ArrayList;

import java.util.List;

public class ZookeeperServer {

static ZooKeeper zooKeeper;

public static void main(String[] args) {

try {

String connectString = "localhost:2181";

int sessionTimeout = 5000;

zooKeeper = new ZooKeeper(connectString, sessionTimeout, new Watcher() {

public void process(WatchedEvent watchedEvent) {

String path = "/servers";

try {

List<String> childrens = zooKeeper.getChildren(path, true);

List<String> hosts = new ArrayList<String>();

for (String child : childrens) {

byte[] dataByte = zooKeeper.getData(path+"/"+child, false, null);

hosts.add(new String(dataByte));

}

System.out.println("启动服务:"+hosts);

} catch (KeeperException e) {

e.printStackTrace();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

});

Thread.sleep(Long.MAX_VALUE);

} catch (Exception e) {

e.printStackTrace();

}

}

}

客户端

import org.apache.zookeeper.CreateMode;

import org.apache.zookeeper.KeeperException;

import org.apache.zookeeper.WatchedEvent;

import org.apache.zookeeper.Watcher;

import org.apache.zookeeper.ZooDefs;

import org.apache.zookeeper.ZooKeeper;

public class ZookeeperClient {

static ZooKeeper zooKeeper;

public static void main(String[] args) {

try {

String connectString = "localhost:2181";

int sessionTimeout = 5000;

zooKeeper = new ZooKeeper(connectString, sessionTimeout, new Watcher() {

public void process(WatchedEvent watchedEvent) {

// 启动userService服务

String serviceName = "userService";

// 设置服务目录

String path = "/servers/node";

try {

zooKeeper.create(path, serviceName.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);

} catch (KeeperException e) {

e.printStackTrace();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

});

Thread.sleep(Long.MAX_VALUE);

} catch (Exception e) {

e.printStackTrace();

}

}

}

先通过zkCli.cmd创建servers节点

create /servers ""

启动ZookeeperServer监听服务，然后启动ZookeeperClient的用户服务，还可以通过zkCli.cmd创建其他节点，打印日志如下

其他

好了今天的zookeeper入门就到这里了，大家有什么问题和建议可以一起沟通下