Zookeeper的簡介和使用

Zookeeper是架構模式是主從結構，用來存儲一些數據，也可以做分佈式協調服務，它的主節點叫leader，從節點叫follower。zookeeper允許一半的節點宕機。它的集羣模式一般是奇數臺服務器。
zookeeper的功能：
1、存儲數據：配置信息，元信息
2、選舉功能
3、數據同步（ZAB協議）
4、分佈式鎖
5、監聽機制，監聽節點的數據變化
單節點的安裝
zookeeper的安裝其實特別簡單。
第一步減壓
tar -zxvf zookeeper-3.4.10.tar.gz -C ~/training/
第二步配置環境變量

vim ~/.bash_profile
ZOOKEEPER_HOME=/root/training/zookeeper-3.4.10
export ZOOKEEPER_HOME
PATH=$ZOOKEEPER_HOME/bin:$PATH
export PATH
使用戶的環境變量配置文件生效
source ~/.bash_profile

第三步配置配置文件
它的配置文件需要把conf 目錄下的示例配置文件拷貝一份
cp zoo_sample.cfg zoo.cfg
因爲啓動zookeeper的時候默認使用的conf目錄下的zoo.cfg配置文件
配置
dataDir=/root/training/zookeeper-3.4.10/tmp 數據存儲的路徑
server.1=bigdata111:2888:3888 2888是通信端口，3888是選舉端口
數據存儲路徑要事先創建好
在/root/training/zookeeper-3.4.10/tmp創建一個文件：myid
輸入 1
啓動：zkServer.sh start
zkServer.sh status
這樣一個單機版zookeeper就安裝成功了

然後同過命令行客戶端測試一下：
zkClli.sh

ZooKeeper節點的類型：兩個維度（永久還是臨時、有序還是無序）
（1）持久化節點
（2）持久化排序節點

	臨時節點：當客戶端會話如果退出，該臨時節點就自動刪除。
	
	（3）臨時節點
	（4）臨時的有序節點

使用代碼操作Zookeeper：
apache提供了一套api接口專門操作zookeeper叫curator
搭建一個簡單maven工程把它引入進去
pom依賴

<dependencies>
  	<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>3.8.1</version>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>org.apache.curator</groupId>
			<artifactId>curator-framework</artifactId>
			<version>4.0.0</version>
		</dependency>

		<dependency>
			<groupId>org.apache.curator</groupId>
			<artifactId>curator-recipes</artifactId>
			<version>4.0.0</version>
		</dependency>

		<dependency>
			<groupId>org.apache.curator</groupId>
			<artifactId>curator-client</artifactId>
			<version>4.0.0</version>
		</dependency>
		<dependency>
			<groupId>org.apache.zookeeper</groupId>
			<artifactId>zookeeper</artifactId>
			<version>3.4.6</version>
		</dependency>

		<dependency>
			<groupId>com.google.guava</groupId>
			<artifactId>guava</artifactId>
			<version>16.0.1</version>
		</dependency>
  </dependencies>

創永久無序節點

package com.kanxyz.demo;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.CreateMode;

public class CreateZKNode
{
	public static void main(String[] args) throws Exception {
		//如果Zookeeper斷掉，設置連接策略                                                              每隔1秒連接一次   最多連接十次    
		RetryPolicy retryPolicy=new ExponentialBackoffRetry(1000, 10);
		CuratorFramework client=CuratorFrameworkFactory.builder()
				 									.connectString("192.168.112.111:2181")
				 									.retryPolicy(retryPolicy)
			 									.build();
		client.start();	
		//創建永久無序節點
		client.create().forPath("/mypath");
		client.close();
	}
}

代碼創建節點可以沒有數據，但是命令行創建節點是創建不上的
創建永久有序節點

package com.kanxyz.demo;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.schema.SchemaSet;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.CreateMode;

public class CreateZKNode
{
	public static void main(String[] args) throws Exception {
		//如果Zookeeper斷掉，設置連接策略                                                              每隔1秒連接一次   最多連接十次    
		RetryPolicy retryPolicy=new ExponentialBackoffRetry(1000, 10);
		CuratorFramework client=CuratorFrameworkFactory.builder()
				 									.connectString("192.168.112.111:2181")
				 									.retryPolicy(retryPolicy)
			 									.build();
		client.start();	
		//創建永久無序節點
//		client.create().forPath("/mypath");
		//創建永久有序節點
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		//創建臨時無序節點
		//創建臨時有序節點
		client.close();
	}
}

創建臨時無序節點和臨時有序節點

package com.kanxyz.demo;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.CreateMode;

public class CreateZKNode
{
	public static void main(String[] args) throws Exception {
		//如果Zookeeper斷掉，設置連接策略                                                              每隔1秒連接一次   最多連接十次    
		RetryPolicy retryPolicy=new ExponentialBackoffRetry(1000, 10);
		CuratorFramework client=CuratorFrameworkFactory.builder()
				 									.connectString("192.168.112.111:2181")
				 									.retryPolicy(retryPolicy)
			 									.build();
		client.start();	
		//創建永久無序節點
//		client.create().forPath("/mypath");
		//創建永久有序節點
		/*client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");
		client.create().withMode(CreateMode.PERSISTENT_SEQUENTIAL).forPath("/node-");*/
		//創建臨時無序節點
		/*client.create().withMode(CreateMode.EPHEMERAL).forPath("/mytempnode");
		Thread.sleep(2000);*/
		//創建臨時有序節點
		client.create().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath("/tmpnode-");
		client.create().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath("/tmpnode-");
		client.create().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath("/tmpnode-");
		client.create().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath("/tmpnode-");
		client.create().withMode(CreateMode.EPHEMERAL_SEQUENTIAL).forPath("/tmpnode-");
		Thread.sleep(5000);
		client.close();
	}
}

節點監聽

package com.kanxyz.demo;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;

public class ListenerZKDemo
{
	public static void main(String[] args) throws Exception{
		RetryPolicy retryPolicy=new ExponentialBackoffRetry(1000, 10);
		CuratorFramework client=CuratorFrameworkFactory.builder()
													  .connectString("192.168.112.111:2181")
													  .retryPolicy(retryPolicy)
													  .build();
		client.start();
		//監聽節點mypath操作
		PathChildrenCache children = new PathChildrenCache(client, "/mypath", true);
		children.getListenable().addListener(new PathChildrenCacheListener()
		{
			
			public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception {
				System.out.println("監控節點的操作："+event.getType());
//				public static final Type CHILD_ADDED; 子節點添加的類型
//		        public static final Type CHILD_UPDATED; 子節點更新的類型
//		        public static final Type CHILD_REMOVED; 子節點移除的類型
				switch (event.getType())
				{
				case CHILD_ADDED:
					System.out.println("節點添加");
					break;
				case CHILD_UPDATED:
					System.out.println("節點更新");
					break;
				case CHILD_REMOVED:
					System.out.println("節點移除");
					break;
				default :
					System.out.println("執行了其他的操作");
					break;
				}
			}
		});
		children.start();
		Thread.sleep(100000);
		client.close();
		System.out.println("監聽結束--------------");
	}
}

分佈式鎖功能

package com.kanxyz.demo;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.ExponentialBackoffRetry;

public class ZKDistributeLock
{
	//秒殺總分數
	private static int NUMBER=10;
	//定義秒殺邏輯
	private static void getNumber(){
		System.out.println("秒殺開始");
		System.out.println("我搶第"+NUMBER+"商品");
		NUMBER--;
		try
		{
			Thread.sleep(1000);
		} catch (InterruptedException e)
		{
			e.printStackTrace();
		}
		System.out.println("秒殺結束");
	}
	public static void main(String[] args) {
		//創建鏈接策略
		RetryPolicy retryPolicy=new ExponentialBackoffRetry(1000, 10);
		//創建客戶端
		CuratorFramework client=CuratorFrameworkFactory.builder()
				.connectString("192.168.112.111:2181")
				.retryPolicy(retryPolicy)
				.build();
		client.start();
		//創建這把鎖
		final InterProcessMutex lock = new InterProcessMutex(client, "/aaaa");
		for (int i = 0; i < 10; i++)
		{
			new Thread(new Runnable()
			{
				public void run() {
					try
					{
						//請求得到鎖
						lock.acquire();
						getNumber();
						
					} catch (Exception e)
					{
						e.printStackTrace();
					}finally {
						try
						{
							//完成本次操作要釋放鎖
							lock.release();
						} catch (Exception e)
						{
							e.printStackTrace();
						}
					}
				}
			}).start();
		}
		//因爲是上邊是線程不能提前關閉鏈接客戶端
		//client.close();
	}
}

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