Zookeeper开源客户端curator

一、curator简介

二、curator使用

三、curator重连策略

四、curator新增节点

五、curator更新节点

六、curator查看节点

七、curator查看子节点

八、curator删除节点

九、总结

一、curator简介

curator是Netflix公司开源的一个zookeeper客户端，curator框架在zookeeper原生API接口上进行了包装，解决了很多zooKeeper客户端非常底层的细节开发。提供zooKeeper各种应用场景(比如：分布式锁服务、集群领导选举、共享计数器、缓存机制、分布式队列等)的抽象封装，实现了Fluent风格的API接口，curator是最好用，最流行的zookeeper的客户端。

原生zookeeperAPI的不足：

连接对象异步创建，需要开发人员自行编码等待；
连接没有自动重连超时机制；
watcher一次注册只生效一次；
不支持递归创建树形节点；

curator特点：

解决session会话超时重连；
watcher监听机制反复注册；
简化开发API；
遵循Fluent风格的API；
提供了分布式锁服务、共享计数器、缓存机制等机制；

二、curator使用

如果需要使用curator框架的话，只需要我们在项目的依赖文件中加入curator的依赖即可，如下：

<dependency><groupId>org.apache.curator</groupId><artifactId>curator-framework</artifactId><version>2.6.0</version><type>jar</type><exclusions><exclusion><groupId>org.apache.zookeeper</groupId><artifactId>zookeeper</artifactId></exclusion></exclusions>
</dependency>
<dependency><groupId>org.apache.zookeeper</groupId><artifactId>zookeeper</artifactId><version>3.4.10</version><type>jar</type>
</dependency>
<dependency><groupId>org.apache.curator</groupId><artifactId>curator-recipes</artifactId><version>2.6.0</version><type>jar</type>
</dependency>

三、curator重连策略

在zookeeper原生API中，当客户端与服务端断开连接后，并不会进行自动重连，curator框架对其封装了一下，允许客户端与服务器端断开连接后，自动根据配置的重连策略进行重连。

一般有下面四种重连策略，都是基于RetryPolicy接口实现的：

public interface RetryPolicy{public boolean  allowRetry(int retryCount, long elapsedTimeMs, RetrySleeper sleeper);
}

RetryOneTime：只重连1次；

/*** RetryOneTime: 5秒后重连一次，只重连1次.*/
RetryPolicy retryOneTime = new RetryOneTime(5000);

RetryNTimes：重连n次；

/*** RetryNTimes: 每5秒重连一次，重连5次.*/
RetryPolicy retryNTimes = new RetryNTimes(5, 5000);

ExponentialBackoffRetry：随着重试次数的增加，每一次重试的时间间隔越来越大；

/*** BoundedExponentialBackoffRetry: 随着重试次数的增加，每一次重试的时间间隔越来越大.* 每一次重试时间： baseSleepTimeMs * Math.max(1, random.nextInt(1 << (retryCount + 1)))*/
RetryPolicy exponentialBackoffRetry = new ExponentialBackoffRetry(1000, 3);

RetryUntilElapsed：每n秒重连一次，总等待时间超过m秒后停止重连；

/*** RetryUntilElapsed: 每5秒重连一次，总等待时间超过10秒后停止重连.*/
RetryPolicy retryUntilElapsed = new RetryUntilElapsed(10000, 5000);

四、curator新增节点

下面分四种情况分别介绍如何使用curator客户端API去操作zookeeper创建节点。

基础代码如下：

package com.wsh.zookeeper.zookeeperapidemo.curator;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Id;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;public class CuratorCreateNodeDemo {private static final Logger logger = LoggerFactory.getLogger(CuratorCreateNodeDemo.class);private static final String ZOOKEEPER_SERVER_ADDRESS = "192.168.179.128:2181,192.168.179.129:2181,192.168.179.133:2181";/*** Curator对象*/private static CuratorFramework curatorFramework;static {//初始化curator对象curatorFramework = CuratorFrameworkFactory.builder()//会话超时时间.sessionTimeoutMs(5000)//服务器集群地址.connectString(ZOOKEEPER_SERVER_ADDRESS)//重试策略.retryPolicy(new ExponentialBackoffRetry(1000, 3))//命名空间,如果制定了命名空间，那么创建的节点的根目录就是/create.namespace("create").build();//开启客户端curatorFramework.start();}/*** 1.创建一个节点*/public void create01() throws Exception {curatorFramework.create()//节点类型：持久化节点.withMode(CreateMode.PERSISTENT)//权限列表  crdwa.withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)//节点路径.forPath("/node1", "node1".getBytes());}/*** 2. 自定义权限列表*/public void create02() throws Exception {List<ACL> aclArrayList = new ArrayList<ACL>();Id id = new Id("ip", "192.168.179.133");aclArrayList.add(new ACL(ZooDefs.Perms.ALL, id));curatorFramework.create()//节点类型：持久化节点.withMode(CreateMode.PERSISTENT)//权限列表.withACL(aclArrayList)//节点路径.forPath("/node2", "node2".getBytes());}/*** 3. 递归创建节点*/public void create03() throws Exception {curatorFramework.create()//当父节点不存在时，自动创建父节点.creatingParentsIfNeeded()//节点类型：持久化节点.withMode(CreateMode.PERSISTENT)//权限列表.withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)//节点路径.forPath("/node3/node31", "node31".getBytes());}/*** 4. 异步方式创建节点*/public void create04() throws Exception {curatorFramework.create()//节点类型：持久化节点.withMode(CreateMode.PERSISTENT)//权限列表.withACL(ZooDefs.Ids.OPEN_ACL_UNSAFE)//异步方式创建节点，匿名内部类实现BackgroundCallback的processResult方法.inBackground(new BackgroundCallback() {@Overridepublic void processResult(CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception {logger.info("节点路径：" + curatorEvent.getPath());logger.info("事件类型：" + curatorEvent.getType());}})//节点路径.forPath("/node4", "node4".getBytes());TimeUnit.SECONDS.sleep(5);}public static void main(String[] args) throws Exception {CuratorCreateNodeDemo curatorCreateNodeDemo = new CuratorCreateNodeDemo();
//        curatorCreateNodeDemo.create01();
//        curatorCreateNodeDemo.create02();
//        curatorCreateNodeDemo.create03();curatorCreateNodeDemo.create04();}}

【a】创建一个节点

我们使用zkCli.sh登录到zookeeper客户端，查看node1节点是否创建成功：

[zk: localhost:2181(CONNECTED) 1] get /create/node1
node1
cZxid = 0x500000003
ctime = Tue Dec 29 11:05:28 CST 2020
mZxid = 0x500000003
mtime = Tue Dec 29 11:05:28 CST 2020
pZxid = 0x500000003
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0

【b】创建一个节点并使用自定义权限列表

可以看到，因为我们node2采用IP地址的授权模式：

[zk: localhost:2181(CONNECTED) 5] get /create/node2
Authentication is not valid : /create/node2

【c】递归创建节点

curator在父节点不存在的时候，会自动帮我们创建父节点，如node3：

[zk: localhost:2181(CONNECTED) 6] ls /create
[node2, node3, node1]
[zk: localhost:2181(CONNECTED) 7] get /create/node3/node31
node31
cZxid = 0x50000000d
ctime = Tue Dec 29 11:09:52 CST 2020
mZxid = 0x50000000d
mtime = Tue Dec 29 11:09:52 CST 2020
pZxid = 0x50000000d
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0

【d】异步方式创建节点

后端日志输出：

11:11:02.643 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorCreateNodeDemo - 节点路径：/node4
11:11:02.644 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorCreateNodeDemo - 事件类型：CREATE

使用zkCli.sh登录到zookeeper客户端，查看node4节点是否创建成功：

[zk: localhost:2181(CONNECTED) 8] get /create/node4
node4
cZxid = 0x500000010
ctime = Tue Dec 29 11:11:02 CST 2020
mZxid = 0x500000010
mtime = Tue Dec 29 11:11:02 CST 2020
pZxid = 0x500000010
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0

五、curator更新节点

基础代码如下：

package com.wsh.zookeeper.zookeeperapidemo.curator;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;public class CuratorUpdateNodeDemo {private static final Logger logger = LoggerFactory.getLogger(CuratorUpdateNodeDemo.class);private static final String ZOOKEEPER_SERVER_ADDRESS = "192.168.179.128:2181,192.168.179.129:2181,192.168.179.133:2181";/*** Curator对象*/private static CuratorFramework curatorFramework;static {//初始化curator对象curatorFramework = CuratorFrameworkFactory.builder()//会话超时时间.sessionTimeoutMs(5000)//服务器集群地址.connectString(ZOOKEEPER_SERVER_ADDRESS)//重试策略.retryPolicy(new ExponentialBackoffRetry(1000, 3))//命名空间,如果制定了命名空间，那么创建的节点的根目录就是/create.namespace("update").build();//开启客户端curatorFramework.start();}/*** 1.更新一个节点*/public void update01() throws Exception {curatorFramework.setData()//节点路径.forPath("/update1", "update11".getBytes());}/*** 2. 指定版本号更新节点*/public void update02() throws Exception {curatorFramework.setData()//当且仅当当前节点数据版本号等于指定的版本号时，才更新数据. 指定-1表示版本号不参与更新判断.withVersion(20)//节点路径.forPath("/update2", "update22".getBytes());}/*** 3. 异步方式更新节点*/public void update03() throws Exception {curatorFramework.setData().inBackground(new BackgroundCallback() {@Overridepublic void processResult(CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception {logger.info("节点路径：" + curatorEvent.getPath());logger.info("事件类型：" + curatorEvent.getType());}})//节点路径.forPath("/update3", "update33".getBytes());Thread.sleep(5000);}public static void main(String[] args) throws Exception {CuratorUpdateNodeDemo curatorUpdateNodeDemo = new CuratorUpdateNodeDemo();
//        curatorUpdateNodeDemo.update01();
//        curatorUpdateNodeDemo.update02();curatorUpdateNodeDemo.update03();}}

我们事先先创建好三个节点用于测试：

[zk: localhost:2181(CONNECTED) 12] create /update "update"
Created /update
[zk: localhost:2181(CONNECTED) 13] create /update/update1 "update1"
Created /update/update1
[zk: localhost:2181(CONNECTED) 14] create /update/update2 "update2"
Created /update/update2
[zk: localhost:2181(CONNECTED) 15] create /update/update3 "update3"
Created /update/update3
[zk: localhost:2181(CONNECTED) 16] ls /update
[update3, update1, update2]

下面分三种情况测试curator更新节点操作：

【a】更新节点

运行程序，使用客户端查看节点数据是否修改成功：

[zk: localhost:2181(CONNECTED) 17] get /update/update1
update11
cZxid = 0x500000016
ctime = Tue Dec 29 11:23:25 CST 2020
mZxid = 0x50000001a
mtime = Tue Dec 29 11:24:02 CST 2020
pZxid = 0x500000016
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 8
numChildren = 0

【b】指定版本号更新节点

运行程序，我们发现后台报如下图错误：

因为当前节点数据版本号为0，我们指定的版本号是20，显然对不上。

【c】异步方式更新节点

运行程序，查看后端日志：

11:26:28.861 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorUpdateNodeDemo - 节点路径：/update3
11:26:28.861 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorUpdateNodeDemo - 事件类型：SET_DATA

然后我们再使用客户端工具查看节点数据是否更新成功：

[zk: localhost:2181(CONNECTED) 19] get /update/update3
update33
cZxid = 0x500000018
ctime = Tue Dec 29 11:23:28 CST 2020
mZxid = 0x500000023
mtime = Tue Dec 29 11:26:28 CST 2020
pZxid = 0x500000018
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 8
numChildren = 0

六、curator查看节点

基础代码如下：

package com.wsh.zookeeper.zookeeperapidemo.curator;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.data.Stat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;public class CuratorGetNodeDateDemo {private static final Logger logger = LoggerFactory.getLogger(CuratorGetNodeDateDemo.class);private static final String ZOOKEEPER_SERVER_ADDRESS = "192.168.179.128:2181,192.168.179.129:2181,192.168.179.133:2181";/*** Curator对象*/private static CuratorFramework curatorFramework;static {//初始化curator对象curatorFramework = CuratorFrameworkFactory.builder()//会话超时时间.sessionTimeoutMs(5000)//服务器集群地址.connectString(ZOOKEEPER_SERVER_ADDRESS)//重试策略.retryPolicy(new ExponentialBackoffRetry(1000, 3))//命名空间.namespace("get").build();//开启客户端curatorFramework.start();}/*** 1.读取节点数据*/public void getData01() throws Exception {byte[] bytes = curatorFramework.getData().forPath("/get1");logger.info("节点数据：" + new String(bytes));}/*** 2. 读取数据时读取节点的属性*/public void getData02() throws Exception {Stat stat = new Stat();curatorFramework.getData().storingStatIn(stat).forPath("/get1");logger.info("节点数据版本号：" + stat.getVersion());logger.info("节点创建事务ID：" + stat.getCzxid());logger.info("节点创建时间：" + stat.getCtime());}/*** 3. 异步方式读取节点的数据*/public void getData03() throws Exception {curatorFramework.getData().inBackground(new BackgroundCallback() {@Overridepublic void processResult(CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception {logger.info("节点路径：" + curatorEvent.getPath());logger.info("事件类型：" + curatorEvent.getType());}}).forPath("/get1");Thread.sleep(5000);}public static void main(String[] args) throws Exception {CuratorGetNodeDateDemo curatorGetNodeDateDemo = new CuratorGetNodeDateDemo();
//        curatorGetNodeDateDemo.getData01();
//        curatorGetNodeDateDemo.getData02();curatorGetNodeDateDemo.getData03();}}

先用客户端工具创建两个节点用于测试：

[zk: localhost:2181(CONNECTED) 32] create /get "get"
Created /get
[zk: localhost:2181(CONNECTED) 33] create /get/get1 "get1"
Created /get/get1

下面分三种情况测试一下curator查看节点API：

【a】读取节点数据

11:54:41.461 [main] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetNodeDateDemo - 节点数据：get1

【b】读取数据时读取节点的属性

11:54:57.172 [main] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetNodeDateDemo - 节点数据版本号：0
11:54:57.173 [main] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetNodeDateDemo - 节点创建事务ID：21474836538
11:54:57.173 [main] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetNodeDateDemo - 节点创建时间：1609214049594

【c】异步方式读取节点的数据

11:55:42.141 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetNodeDateDemo - 节点路径：/get1
11:55:42.141 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetNodeDateDemo - 事件类型：GET_DATA

七、curator查看子节点

基础代码如下：

package com.wsh.zookeeper.zookeeperapidemo.curator;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.util.List;public class CuratorGetChildrenNodeDateDemo {private static final Logger logger = LoggerFactory.getLogger(CuratorGetChildrenNodeDateDemo.class);private static final String ZOOKEEPER_SERVER_ADDRESS = "192.168.179.128:2181,192.168.179.129:2181,192.168.179.133:2181";/*** Curator对象*/private static CuratorFramework curatorFramework;static {//初始化curator对象curatorFramework = CuratorFrameworkFactory.builder()//会话超时时间.sessionTimeoutMs(5000)//服务器集群地址.connectString(ZOOKEEPER_SERVER_ADDRESS)//重试策略.retryPolicy(new ExponentialBackoffRetry(1000, 3))//命名空间.namespace("children").build();//开启客户端curatorFramework.start();}/*** 1.读取子节点数据*/public void getChildrenData01() throws Exception {List<String> list = curatorFramework.getChildren().forPath("/children1");for (String child : list) {logger.info("节点路径：" + child);}}/*** 2. 异步方式读取子节点的数据*/public void getChildrenData02() throws Exception {curatorFramework.getChildren().inBackground(new BackgroundCallback() {@Overridepublic void processResult(CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception {logger.info("节点路径：" + curatorEvent.getPath());logger.info("事件类型：" + curatorEvent.getType());List<String> children = curatorEvent.getChildren();for (String child : children) {logger.info("子节点路径：" + child);}}}).forPath("/children1");Thread.sleep(5000);}public static void main(String[] args) throws Exception {CuratorGetChildrenNodeDateDemo curatorGetChildrenNodeDateDemo = new CuratorGetChildrenNodeDateDemo();
//        curatorGetChildrenNodeDateDemo.getChildrenData01();curatorGetChildrenNodeDateDemo.getChildrenData02();}}

使用客户端工具先创建好几个节点用于测试：

[zk: localhost:2181(CONNECTED) 34] create /children "children"
Created /children
[zk: localhost:2181(CONNECTED) 35] create /children/children1 "children1"
Created /children/children1
[zk: localhost:2181(CONNECTED) 36] create /children/children1/node1 "node1"
Created /children/children1/node1
[zk: localhost:2181(CONNECTED) 37] create /children/children1/node2 "node2"
Created /children/children1/node2

下面我们分两种情况测试一下curator查看子节点API：

【a】读取子节点数据

13:38:02.000 [main] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetChildrenNodeDateDemo - 节点路径：node2
13:38:02.000 [main] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetChildrenNodeDateDemo - 节点路径：node1

【b】异步方式读取子节点数据

13:39:10.309 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetChildrenNodeDateDemo - 节点路径：/children1
13:39:10.309 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetChildrenNodeDateDemo - 事件类型：CHILDREN
13:39:10.309 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetChildrenNodeDateDemo - 子节点路径：node2
13:39:10.309 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorGetChildrenNodeDateDemo - 子节点路径：node1

八、curator删除节点

基础代码如下：

package com.wsh.zookeeper.zookeeperapidemo.curator;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.api.BackgroundCallback;
import org.apache.curator.framework.api.CuratorEvent;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;import java.util.concurrent.TimeUnit;public class CuratorDeleteNodeDemo {private static final Logger logger = LoggerFactory.getLogger(CuratorDeleteNodeDemo.class);private static final String ZOOKEEPER_SERVER_ADDRESS = "192.168.179.128:2181,192.168.179.129:2181,192.168.179.133:2181";/*** Curator对象*/private static CuratorFramework curatorFramework;static {//初始化curator对象curatorFramework = CuratorFrameworkFactory.builder()//会话超时时间.sessionTimeoutMs(5000)//服务器集群地址.connectString(ZOOKEEPER_SERVER_ADDRESS)//重试策略.retryPolicy(new ExponentialBackoffRetry(1000, 3))//命名空间.namespace("delete").build();//开启客户端curatorFramework.start();}/*** 1.删除一个节点*/public void delete01() throws Exception {curatorFramework.delete().forPath("/delete1");}/*** 2. 指定版本号删除节点*/public void delete02() throws Exception {curatorFramework.delete()//指定版本号.withVersion(20).forPath("/delete2");}/*** 3. 递归删除节点*/public void delete03() throws Exception {curatorFramework.delete()//当删除节点存在子节点时，一并删除子节点.deletingChildrenIfNeeded().forPath("/delete3");}/*** 4. 异步方式删除节点*/public void delete04() throws Exception {curatorFramework.delete().inBackground(new BackgroundCallback() {@Overridepublic void processResult(CuratorFramework curatorFramework, CuratorEvent curatorEvent) throws Exception {logger.info("节点路径：" + curatorEvent.getPath());logger.info("事件类型：" + curatorEvent.getType());}}).forPath("/delete4");TimeUnit.SECONDS.sleep(5);}public static void main(String[] args) throws Exception {CuratorDeleteNodeDemo curatorDeleteNodeDemo = new CuratorDeleteNodeDemo();
//        curatorDeleteNodeDemo.delete01();
//        curatorDeleteNodeDemo.delete02();
//        curatorDeleteNodeDemo.delete03();curatorDeleteNodeDemo.delete04();}}

先使用客户端创建好几个节点：

[zk: localhost:2181(CONNECTED) 20] create /delete "delete"
Created /delete
[zk: localhost:2181(CONNECTED) 21] create /delete/delete1 "delete1"
Created /delete/delete1
[zk: localhost:2181(CONNECTED) 22] create /delete/delete2 "delete2"
Created /delete/delete2
[zk: localhost:2181(CONNECTED) 23] create /delete/delete3 "delete3"
Created /delete/delete3
[zk: localhost:2181(CONNECTED) 24] create /delete/delete3/node1 "node1"
Created /delete/delete3/node1
[zk: localhost:2181(CONNECTED) 25] create /delete/delete4 "delete4"
Created /delete/delete4

下面我们分四种情况分别测试一下curator删除节点的API：

【a】删除一个节点

[zk: localhost:2181(CONNECTED) 26] get /delete/delete1
Node does not exist: /delete/delete1

【b】指定版本号删除节点

当前节点数据版本号如下图：

因为我们程序里面指定的是20，与当前版本对不上，所以后端抛出如下图异常：

【c】递归删除节点

[zk: localhost:2181(CONNECTED) 28] ls /delete/delete3   #删除之前
[node1]
[zk: localhost:2181(CONNECTED) 29] ls /delete/delete3   #删除之后
Node does not exist: /delete/delete3

【d】异步方式删除节点

11:43:36.571 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorDeleteNodeDemo - 节点路径：/delete4
11:43:36.571 [main-EventThread] INFO com.wsh.zookeeper.zookeeperapidemo.curator.CuratorDeleteNodeDemo - 事件类型：DELETE

再次使用客户端查看，可以看到节点已经成功删除。

[zk: localhost:2181(CONNECTED) 30] get /delete/delete4
Node does not exist: /delete/delete4

九、总结

本篇文章主要总结了zookeeper一个开源的客户端curator，并通过案例详细说明了如何使用curator进行节点的创建、修改、删除等操作，更多API操作可以参见curator的官网进行学习。