命令基本语法	功能描述
help	显示所有操作命令
ls path [watch]	使用 ls 命令来查看当前znode中所包含的内容
ls2 path [watch]	查看当前节点数据并能看到更新次数等数据
create	普通创建-s 含有序列-e 临时（重启或者超时消失）
get path [watch]	获得节点的值
set	设置节点的具体值
stat	查看节点状态
delete	删除节点
rmr	递归删除节点

1．启动客户端

[atguigu@hadoop103 zookeeper-3.4.10]$ bin/zkCli.sh

2．显示所有操作命令

[zk: localhost:2181(CONNECTED) 1] help

3．查看当前znode中所包含的内容

[zk: localhost:2181(CONNECTED) 0] ls /

[zookeeper]

4．查看当前节点详细数据

[zk: localhost:2181(CONNECTED) 1] ls2 /

[zookeeper]

cZxid = 0x0

ctime = Thu Jan 01 08:00:00 CST 1970

mZxid = 0x0

mtime = Thu Jan 01 08:00:00 CST 1970

[zk: localhost:2181(CONNECTED) 3] create /sanguo "jinlian"

Created /sanguo

[zk: localhost:2181(CONNECTED) 4] create /sanguo/shuguo "liubei"

Created /sanguo/shuguo

6．获得节点的值

[zk: localhost:2181(CONNECTED) 5] get /sanguo

jinlian

cZxid = 0x100000003

ctime = Wed Aug 29 00:03:23 CST 2018

mZxid = 0x100000003

mtime = Wed Aug 29 00:03:23 CST 2018

[zk: localhost:2181(CONNECTED) 6]

[zk: localhost:2181(CONNECTED) 6] get /sanguo/shuguo

liubei

cZxid = 0x100000004

ctime = Wed Aug 29 00:04:35 CST 2018

mZxid = 0x100000004

mtime = Wed Aug 29 00:04:35 CST 2018

[zk: localhost:2181(CONNECTED) 7] create -e /sanguo/wuguo "zhouyu"

Created /sanguo/wuguo

（1）在当前客户端是能查看到的

[zk: localhost:2181(CONNECTED) 3] ls /sanguo

[wuguo, shuguo]

（2）退出当前客户端然后再重启客户端

[zk: localhost:2181(CONNECTED) 12] quit

[atguigu@hadoop104 zookeeper-3.4.10]$ bin/zkCli.sh

（3）再次查看根目录下短暂节点已经删除

[zk: localhost:2181(CONNECTED) 0] ls /sanguo

[shuguo]

8．创建带序号的节点

（1）先创建一个普通的根节点/sanguo/weiguo

[zk: localhost:2181(CONNECTED) 1] create /sanguo/weiguo "caocao"

Created /sanguo/weiguo

（2）创建带序号的节点

[zk: localhost:2181(CONNECTED) 2] create -s /sanguo/weiguo/xiaoqiao "jinlian"

Created /sanguo/weiguo/xiaoqiao0000000000

[zk: localhost:2181(CONNECTED) 3] create -s /sanguo/weiguo/daqiao "jinlian"

Created /sanguo/weiguo/daqiao0000000001

[zk: localhost:2181(CONNECTED) 4] create -s /sanguo/weiguo/diaocan "jinlian"

Created /sanguo/weiguo/diaocan0000000002

如果原来没有序号节点，序号从0开始依次递增。如果原节点下已有2个节点，则再排序时从2开始，以此类推。

9．修改节点数据值

[zk: localhost:2181(CONNECTED) 6] set /sanguo/weiguo "simayi"

10．节点的值变化监听

（1）在hadoop104主机上注册监听/sanguo节点数据变化

[zk: localhost:2181(CONNECTED) 26] [zk: localhost:2181(CONNECTED) 8] get /sanguo watch

（2）在hadoop103主机上修改/sanguo节点的数据

[zk: localhost:2181(CONNECTED) 1] set /sanguo "xisi"

（3）观察hadoop104主机收到数据变化的监听

WATCHER::

WatchedEvent state:SyncConnected type:NodeDataChanged path:/sanguo

11．节点的子节点变化监听（路径变化）

（1）在hadoop104主机上注册监听/sanguo节点的子节点变化

[zk: localhost:2181(CONNECTED) 1] ls /sanguo watch

[aa0000000001, server101]

（2）在hadoop103主机/sanguo节点上创建子节点

[zk: localhost:2181(CONNECTED) 2] create /sanguo/jin "simayi"

Created /sanguo/jin

（3）观察hadoop104主机收到子节点变化的监听

WATCHER::

WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/sanguo

12．删除节点

[zk: localhost:2181(CONNECTED) 4] delete /sanguo/jin

13．递归删除节点

[zk: localhost:2181(CONNECTED) 15] rmr /sanguo/shuguo

14．查看节点状态

[zk: localhost:2181(CONNECTED) 17] stat /sanguo

cZxid = 0x100000003

ctime = Wed Aug 29 00:03:23 CST 2018

mZxid = 0x100000011

mtime = Wed Aug 29 00:21:23 CST 2018

4.3 API应用

4.3.1 Eclipse环境搭建

1．创建一个Maven工程

2．添加pom文件

junit junit RELEASE org.apache.logging.log4j log4j-core 2.8.2 org.apache.zookeeper zookeeper 3.4.10

3．拷贝log4j.properties文件到项目根目录

需要在项目的src/main/resources目录下，新建一个文件，命名为"log4j.properties"，在文件中填入。

log4j.rootLogger=INFO, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n

log4j.appender.logfile=org.apache.log4j.FileAppender

log4j.appender.logfile.File=target/spring.log

log4j.appender.logfile.layout=org.apache.log4j.PatternLayout

log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n

private static String connectString ="hadoop102:2181,hadoop103:2181,hadoop104:2181"; private static int sessionTimeout = 2000; private ZooKeeper zkClient = null; @Before public void init() throws Exception { zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { // 收到事件通知后的回调函数（用户的业务逻辑） System.out.println(event.getType() + "--" + event.getPath()); // 再次启动监听 try { zkClient.getChildren("/", true); } catch (Exception e) { e.printStackTrace(); } } }); }

4.3.3 创建子节点

// 创建子节点@Testpublic void create() throws Exception { // 参数1：要创建的节点的路径；参数2：节点数据；参数3：节点权限；参数4：节点的类型 String nodeCreated = zkClient.create("/atguigu", "jinlian".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);}

4.3.4 获取子节点并监听节点变化

// 获取子节点@Testpublic void getChildren() throws Exception { List children = zkClient.getChildren("/", true); for (String child : children) { System.out.println(child); } // 延时阻塞 Thread.sleep(Long.MAX_VALUE);}

4.3.5 判断Znode是否存在

// 判断znode是否存在@Testpublic void exist() throws Exception { Stat stat = zkClient.exists("/eclipse", false); System.out.println(stat == null ? "not exist" : "exist");}

4.4 监听服务器节点动态上下线案例

1．需求

某分布式系统中，主节点可以有多台，可以动态上下线，任意一台客户端都能实时感知到主节点服务器的上下线。

[zk: localhost:2181(CONNECTED) 10] create /servers "servers"

Created /servers

（1）服务器端向Zookeeper注册代码

package com.atguigu.zkcase;import java.io.IOException;import org.apache.zookeeper.CreateMode;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.ZooKeeper;import org.apache.zookeeper.ZooDefs.Ids; public class DistributeServer { private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private static int sessionTimeout = 2000; private ZooKeeper zk = null; private String parentNode = "/servers"; // 创建到zk的客户端连接 public void getConnect() throws IOException{ zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { } }); } // 注册服务器 public void registServer(String hostname) throws Exception{ String create = zk.create(parentNode + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); System.out.println(hostname +" is online "+ create); } // 业务功能 public void business(String hostname) throws Exception{ System.out.println(hostname+" is working ..."); Thread.sleep(Long.MAX_VALUE); } public static void main(String[] args) throws Exception { // 1获取zk连接 DistributeServer server = new DistributeServer(); server.getConnect(); // 2 利用zk连接注册服务器信息 server.registServer(args[0]); // 3 启动业务功能 server.business(args[0]); }}

（2）客户端代码

package com.atguigu.zkcase;import java.io.IOException;import java.util.ArrayList;import java.util.List;import org.apache.zookeeper.WatchedEvent;import org.apache.zookeeper.Watcher;import org.apache.zookeeper.ZooKeeper; public class DistributeClient { private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181"; private static int sessionTimeout = 2000; private ZooKeeper zk = null; private String parentNode = "/servers"; // 创建到zk的客户端连接 public void getConnect() throws IOException { zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { // 再次启动监听 try { getServerList(); } catch (Exception e) { e.printStackTrace(); } } }); } // 获取服务器列表信息 public void getServerList() throws Exception { // 1获取服务器子节点信息，并且对父节点进行监听 List children = zk.getChildren(parentNode, true); // 2存储服务器信息列表 ArrayList servers = new ArrayList<>(); // 3遍历所有节点，获取节点中的主机名称信息 for (String child : children) { byte[] data = zk.getData(parentNode + "/" + child, false, null); servers.add(new String(data)); } // 4打印服务器列表信息 System.out.println(servers); } // 业务功能 public void business() throws Exception{ System.out.println("client is working ...");Thread.sleep(Long.MAX_VALUE); } public static void main(String[] args) throws Exception { // 1获取zk连接 DistributeClient client = new DistributeClient(); client.getConnect(); // 2获取servers的子节点信息，从中获取服务器信息列表 client.getServerList(); // 3业务进程启动 client.business(); }}

第5章企业面试真题

（3）集群最少需要机器数：3

5.4 ZooKeeper的常用命令

ls create get delete set…

zookeeper

大数据技术之Zookeeper

第1章 Zookeeper入门

1.1 概述

1.2 特点

1.3 数据结构

1.4 应用场景

1.5 下载地址

第2章 Zookeeper安装

2.1 本地模式安装部署

2.2 配置参数解读

第3章 Zookeeper内部原理

3.1 选举机制（面试重点）

3.2 节点类型

3.3 Stat结构体

3.4 监听器原理（面试重点）

3.5 写数据流程

第4章 Zookeeper实战（开发重点）

4.1 分布式安装部署

4.2 客户端命令行操作

4.3 API应用

4.3.1 Eclipse环境搭建

4.3.2 创建ZooKeeper客户端

4.3.3 创建子节点

4.3.4 获取子节点并监听节点变化

4.3.5 判断Znode是否存在

4.4 监听服务器节点动态上下线案例

第5章企业面试真题

5.1 请简述ZooKeeper的选举机制

5.2 ZooKeeper的监听原理是什么？

5.3 ZooKeeper的部署方式有哪几种？集群中的角色有哪些？集群最少需要几台机器？

5.4 ZooKeeper的常用命令