ZooKeeper演示案例

1 客户端命令行操作

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

[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 = 0x0ctime = Thu Jan 01 08:00:00 CST 1970mZxid = 0x0mtime = Thu Jan 01 08:00:00 CST 1970pZxid = 0x0cversion = -1dataVersion = 0aclVersion = 0ephemeralOwner = 0x0dataLength = 0numChildren = 1

5．分别创建2个普通节点

[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 /sanguojinliancZxid = 0x100000003ctime = Wed Aug 29 00:03:23 CST 2018mZxid = 0x100000003mtime = Wed Aug 29 00:03:23 CST 2018pZxid = 0x100000004cversion = 1dataVersion = 0aclVersion = 0ephemeralOwner = 0x0dataLength = 7numChildren = 1[zk: localhost:2181(CONNECTED) 6][zk: localhost:2181(CONNECTED) 6] get /sanguo/shuguoliubeicZxid = 0x100000004ctime = Wed Aug 29 00:04:35 CST 2018mZxid = 0x100000004mtime = Wed Aug 29 00:04:35 CST 2018pZxid = 0x100000004cversion = 0dataVersion = 0aclVersion = 0ephemeralOwner = 0x0dataLength = 6numChildren = 0

7．创建短暂节点

[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[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 /sanguocZxid = 0x100000003ctime = Wed Aug 29 00:03:23 CST 2018mZxid = 0x100000011mtime = Wed Aug 29 00:21:23 CST 2018pZxid = 0x100000014cversion = 9dataVersion = 1aclVersion = 0ephemeralOwner = 0x0dataLength = 4numChildren = 1

2 API应用

环境搭建

1．创建一个Maven工程

2．添加pom文件

<dependencies><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>RELEASE</version></dependency><dependency><groupId>org.apache.logging.log4j</groupId><artifactId>log4j-core</artifactId><version>2.8.2</version></dependency><!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper --><dependency><groupId>org.apache.zookeeper</groupId><artifactId>zookeeper</artifactId><version>3.4.10</version></dependency></dependencies>

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

创建ZooKeeper客户端

//注意：在connectString中，不能有空格，否则会报java.net.UnknownHostException异常private static final String CONNECT_STRING = "CentOS001:2181,CentOS004:2181,CentOS005:2181";private int SESSION_TIMEOUT = 2000;private ZooKeeper zkClient;@Beforepublic void init() throws IOException {zkClient = new ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, new Watcher() {@Overridepublic void process(WatchedEvent event) {System.out.println("---------start----------");// 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());List<String> children;// 再次启动监听try {children = zkClient.getChildren("/", true);for (String child : children) {System.out.println(child);}System.out.println("---------end----------");} catch (KeeperException |InterruptedException e) {e.printStackTrace();}}});}

创建子节点

/*** 1 创建节点* @throws KeeperException* @throws InterruptedException*/@Testpublic void createNode() throws KeeperException, InterruptedException {String path = zkClient.create("/htzw", "hangtian".getBytes(), Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);System.out.println(path);}

获取子节点并监听节点变化

/*** 2 获取子节点 并监控节点的变化* @throws KeeperException* @throws InterruptedException*/@Testpublic void getDataAndWatch() throws KeeperException, InterruptedException {List<String> children = zkClient.getChildren("/", true);for (String child : children) {System.out.println(child);}// 延时阻塞Thread.sleep(Long.MAX_VALUE);}

判断Znode是否存在

/*** 3 判断节点是否存在* @throws KeeperException* @throws InterruptedException*/@Testpublic void exist() throws KeeperException, InterruptedException {Stat stat = zkClient.exists("/htzw", false);System.out.println(stat == null ? "not exist" : "exist");}

3 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。

2．需求分析，如图5-12所示

服务器动态上下线案例分析

3．具体实现

（0）先在集群上创建/servers节点

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

（1）服务器端向Zookeeper注册代码

public class DistributeServer {private static final String CONNECT_STRING = "CentOS001:2181,CentOS004:2181,CentOS005:2181";private static final int SESSION_TIMEOUT = 2000;private ZooKeeper zkClient;/*** 创建到zk的客户端连接* @throws IOException*/private void getConnect() throws IOException {zkClient = new ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, event -> {});}private void business() throws InterruptedException {System.out.println("working ...");Thread.sleep(Long.MAX_VALUE);}/*** 注册服务器* @param hostname* @throws KeeperException* @throws InterruptedException*/private void registerServer(String hostname) throws KeeperException, InterruptedException {String path = zkClient.create("/servers/server", hostname.getBytes(),Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);System.out.println(hostname + "is online ---psth:"+path);}public static void main(String[] args) throws Exception {DistributeServer server = new DistributeServer();// 1 连接zookeeper集群server.getConnect();// 2 注册节点server.registerServer("10.0.1.55");// 3 业务逻辑处理server.business();}
}

（2）客户端代码

public class DistributeClient {private String CONNECT_STRING = "CentOS001:2181,CentOS004:2181,CentOS005:2181";private int SESSION_TIMEOUT = 2000;private ZooKeeper zkClient;/*** 业务功能* @throws InterruptedException*/private void business() throws InterruptedException {System.out.println("client is working ...");Thread.sleep(Long.MAX_VALUE);}/*** 获取服务器列表信息* @throws KeeperException* @throws InterruptedException*/private void getServerList() throws KeeperException, InterruptedException {//获取服务器子节点信息，并且对父节点进行监听List<String> children = zkClient.getChildren("/servers", true);// 存储服务器节点主机名称集合ArrayList<String> hosts = new ArrayList<>();// 遍历所有节点，获取节点中的主机名称信息for (String child : children) {byte[] data = zkClient.getData("/servers/" + child, false, null);hosts.add(new String(data));}// 将所有在线主机名称打印到控制台System.out.println("*****************************");System.out.println(hosts);System.out.println("*****************************");}/*** 创建到zk的客户端连接* @throws IOException*/private void getConnect() throws IOException {zkClient = new ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, event -> {// 再次启动监听try {getServerList();} catch (Exception e) {e.printStackTrace();}});}public static void main(String[] args) throws Exception {DistributeClient client = new DistributeClient();// 1 获取zookeeper集群连接client.getConnect();// 2 注册监听client.getServerList();// 3 业务逻辑处理client.business();}
}