ZooKeeper学习笔记四 ZooKeeper基本使用

Windows单机版本安装

下载zookeeper windows3.3.6
把conf/zoo_sample.cfg改名为zoo.cfg

# The number of milliseconds of each tick
tickTime=2000
# The number of ticks that the initial 
# synchronization phase can take
initLimit=10
# The number of ticks that can pass between 
# sending a request and getting an acknowledgement
syncLimit=5
# the directory where the snapshot is stored.
dataDir=D:\\tools\\zookeeper-3.3.6
dataLogDir=D:\\tools\\zookeeper-3.3.6
# the port at which the clients will connect
clientPort=2181

1、tickTime：这个时间是作为Zookeeper 服务器之间或客户端与服务器之间维持心跳的时间间隔，也就是每个 tickTime 时间就会发送一个心跳。

2、dataDir：顾名思义就是Zookeeper 保存数据的目录，默认情况下，Zookeeper 将写数据的日志文件也保存在这个目录里。

3、dataLogDir：顾名思义就是Zookeeper 保存日志文件的目录

4、clientPort：这个端口就是客户端连接Zookeeper 服务器的端口，Zookeeper 会监听这个端口，接受客户端的访问请求。

启动
进入到bin目录，并且启动zkServer.cmd

启动jps命令，会看到一个QuorumPeerMain进程 ：

CentOS7 服务端安装

mkdir -p /usr/local/services/zookeeper
cd /usr/local/services/zookeeper
wget https://mirrors.tuna.tsinghua.edu.cn/apache/zookeeper/zookeeper-3.4.12/zookeeper-3.4.12.tar.gz
tar -zxvf zookeeper-3.4.9.tar.gz
cd zookeeper-3.4.9/conf/
cp zoo_sample.cfg zoo.cfg
vim zoo.cfg

修改：

# 数据文件夹
dataDir=/usr/local/services/zookeeper/zookeeper-3.4.12/data
 
# 日志文件夹
dataLogDir=/usr/local/services/zookeeper/zookeeper-3.4.12/logs

保存并退出。

cd ../bin/
vim /etc/profile

增加：

 
export ZOOKEEPER_HOME=/usr/local/services/zookeeper/zookeeper-3.4.12/
export PATH=$ZOOKEEPER_HOME/bin:$PATH
export PATH

保存并退出。

source /etc/profile
zkServer.sh start

命令：

# 查询状态
zkServer.sh status
# 关闭zookeeper
zkServer.sh stop
# 重启
zkServer.sh restart

设置自动启动

在/etc/rc.local文件中追加：

# java_home
#export JAVA_HOME=/usr/java/jdk1.8.0_66
# zookeeper
/usr/local/services/zookeeper/zookeeper-3.4.12/bin/zkServer.sh start

测试客户端

连接

zkCli -server 127.0.0.1:2181

创建节点

create [-s] [-e] path data acl

-s 或 -e分别指定节点特性，顺序或临时节点。默认情况下，创建的是持久节点。
acl是进行权限控制的。

create /zk-book 123    #创建/zk-book节点，内容是123

读取结点

ls /zk-book
ls /

读取内容

get path [watch]

更新结点
set path data [version]

删除

delete path [version]

注意 ， 无法删除一个有子节点的节点。

Java客户端API使用

文档：http://zookeeper.apache.org/doc/r3.4.6/api/index.html

连接、查询

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooKeeper;

public class ZooKeeper_Constructor_Usage_Simple {

	public static void main(String[] args) throws IOException {
		String hostPort = "localhost:2181";
	    String zpath = "/";
	    List  zooChildren = new ArrayList();
	    ZooKeeper zk = new ZooKeeper(hostPort, 2000, null);
	    if (zk != null) {
	      try {
	        zooChildren = zk.getChildren(zpath, false);
	        System.out.println("Znodes of '/': ");
	        for (String child: zooChildren) {
	          //print the children
	          System.out.println(child);
	        }
	      } catch (KeeperException e) {
	        e.printStackTrace();
	      } catch (InterruptedException e) {
	        e.printStackTrace();
	      }
	    }

	}

}

输出：

ZooKeeper的构造函数最多有5个参数：

ZooKeeper(String connectString, int sessionTimeout, Watcher watcher, long sessionId, byte[] sessionPasswd)

创建结点

String create(final String path,
              byte data[],
              List acl,
              CreateMode createMode)
void create(final String path,
              byte data[],
              List acl,
              CreateMode createMode,
              StringCallback cb,Object ctx)

这两个接口分别以同步和异步方式创建节点。

目前ZooKeeper的节点的内容只支持字节数组类型，使用者需要自己进行序列化和反序列化。

package zookeeper;

import java.io.IOException;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;

public class ZooKeeper_Create_API_Sync_Usage implements Watcher {

	private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
	public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
		String hostPort = "localhost:2181";
	    ZooKeeper zookeeper = new ZooKeeper(hostPort,5000,new ZooKeeper_Create_API_Sync_Usage());
	    connectedSemaphore.await();
	    String path1 = zookeeper.create("/zk-test-ephemeral-","".getBytes(),
	    		Ids.OPEN_ACL_UNSAFE,
	    		CreateMode.EPHEMERAL);
	    System.out.println("Success create znode:"+path1);
	    String path2 = zookeeper.create("/zk-test-ephemeral-","".getBytes(),Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
	    System.out.println("Success create znode:"+path2);

	}

	@Override
	public void process(WatchedEvent event) {
		if(KeeperState.SyncConnected == event.getState()){
			connectedSemaphore.countDown();
		}
		
	}

}

结果：

Success create znode:/zk-test-ephemeral-
Success create znode:/zk-test-ephemeral-0000000020

使用同步API更新节点数据内容

package zookeeper;

import java.util.concurrent.CountDownLatch;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class SetData_API_Sync_Usage implements Watcher {
	private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
	private static ZooKeeper zk;
	
	public static void main(String[] args) throws Exception{
		String path = "/zk-book";
		zk = new ZooKeeper("127.0.0.1:2181",5000, new SetData_API_Sync_Usage());
		connectedSemaphore.await();

		zk.create(path, "123".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
		zk.getData(path, true, null);
		
		Stat stat = zk.setData(path,"456".getBytes(),-1);
		System.out.println(stat.getCzxid()+","+stat.getMzxid()+","+stat.getVersion());
		Stat stat2 = zk.setData(path, "456".getBytes(), stat.getVersion());
		System.out.println(stat2.getCzxid()+","+stat2.getMzxid()+"," + stat2.getVersion());
		
		try{
			zk.setData(path, "456".getBytes(), stat.getVersion());
		}catch(KeeperException e){
			System.out.println("Error:"+e.code() + "," + e.getMessage());
		}
		
	}
	public void process(WatchedEvent event){
		if(KeeperState.SyncConnected == event.getState()){
			if(EventType.None == event.getType() && null == event.getPath()){
				connectedSemaphore.countDown();
			}
		}
	}
}

异步更新
使用：async接口。

检测节点是否存在

public Stat exists(final String path,Watcher watcher)
public Stat exists(String path,boolean watch)
public void exists(final String path,Watcher watcher,StatCallback cb,Object ctx)
public void exists(String path,boolean watch,StatCallback cb,Object ctx)

权限控制
ZooKeeper客户端提供了接口进行权限控制：

addAuthInfo(String scheme,byte[] auth)