一、zookeeper--部署和使用

一、部署zookeeper

1、資源規(guī)劃

2、集群部署

（1）安裝zk

[root@bigdata121 modules]# cd /opt/modules/zookeeper-3.4.10
[root@bigdata121 zookeeper-3.4.10]# mkdir zkData
[root@bigdata121 zookeeper-3.4.10]# mv conf/zoo_sample.cfg conf/zoo.cfg

（2）修改zoo.cfg配置

# 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.
# do not use /tmp for storage, /tmp here is just 
# example sakes.
#dataDir=/tmp/zookeeper

# 指定zk存儲(chǔ)數(shù)據(jù)的目錄
dataDir=/opt/modules/zookeeper-3.4.10/zkData
# the port at which the clients will connect
clientPort=2181
# the maximum number of client connections.
# increase this if you need to handle more clients
#maxClientCnxns=60
#
# Be sure to read the maintenance section of the 
# administrator guide before turning on autopurge.
#
# http://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_maintenance
#
# The number of snapshots to retain in dataDir
#autopurge.snapRetainCount=3
# Purge task interval in hours
# Set to "0" to disable auto purge feature
#autopurge.purgeInterval=1

# 這里是重點(diǎn)配置
#############cluster#############################
server.1=bigdata121:2888:3888
server.2=bigdata122:2888:3888
server.3=bigdata123:2888:3888

cluster配置參數(shù)解讀：
Server.A=B:C:D。
A是一個(gè)數(shù)字，表示這個(gè)是第幾號(hào)服務(wù)器，也就是sid；
B是這個(gè)服務(wù)器的ip地址；
C是這個(gè)服務(wù)器與集群中的Leader服務(wù)器交換信息的端口；不是對(duì)外的服務(wù)端口（對(duì)外的服務(wù)端口默認(rèn)是2181）
D是萬(wàn)一集群中的Leader服務(wù)器掛了，需要一個(gè)端口來(lái)重新進(jìn)行選舉，選出一個(gè)新的Leader，而這個(gè)端口就是用來(lái)執(zhí)行選舉時(shí)服務(wù)器相互通信的端口。

將配置好的整個(gè)程序目錄拷貝到其他機(jī)器上，使用scp或者rsync都可以，自己看著辦

（3）指定服務(wù)器id
在前面配置的 dataDir 指定的目錄下，創(chuàng)建一個(gè)“myid”文件，里面的內(nèi)容就寫入當(dāng)前server的id，這個(gè)id就是在zk集群中的唯一標(biāo)識(shí)。并且這個(gè)id需要和前面配置文件中的cluster中指定的一樣，否則會(huì)報(bào)錯(cuò)。

（4）配置環(huán)境變量

vim /etc/profile.d/zookeeper.sh

#!/bin/bash
export ZOOKEEPER_HOME=/opt/modules/zookeeper-3.4.10
export PATH=${ZOOKEEPER_HOME}/bin:$PATH

然后 
source /etc/profile.d/zookeeper.sh

（5）啟動(dòng)
在三臺(tái)機(jī)器上執(zhí)行

啟動(dòng)：zkServer.sh start
查看當(dāng)前主機(jī)上zk的狀態(tài)：zkServer.sh status
[root@bigdata121 conf]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower

二、常用命令

使用 zkCli.sh 進(jìn)入本機(jī)的zk服務(wù)。
可以使用如下命令：

三、zk api使用（java）

1、maven依賴

<dependencies>
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.10</version>
        </dependency>
</dependencies>

2、創(chuàng)建zk客戶端

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.util.List;

public class ZkTest {
    public static String connectString = "bigdata121:2181,bigdata122:2181,bigdata123:2181";
    public static int sessionTimeout = 2000;
    public ZooKeeper zkClient = null;

    @Before
    public void init() throws IOException {
        //創(chuàng)建zk客戶端
        zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            //返回監(jiān)聽(tīng)事件時(shí)的處理函數(shù)，監(jiān)聽(tīng)事件是一次性的
            public void process(WatchedEvent watchedEvent) {
                System.out.println(watchedEvent.getState() + "," + watchedEvent.getType() + "," + watchedEvent.getPath());

                try {
                    zkClient.getChildren("/", true);
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

3、創(chuàng)建節(jié)點(diǎn)

public void create() {
        //創(chuàng)建節(jié)點(diǎn)，參數(shù)為：節(jié)點(diǎn)名 節(jié)點(diǎn)值 權(quán)限 節(jié)點(diǎn)類型
        //即 /wangjin  tao  開(kāi)放權(quán)限  持久化節(jié)點(diǎn)
        try {
            String s = zkClient.create("/wangjin", "tao".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        } catch (KeeperException e) {
            System.out.println("node exists!!!");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

4、獲取子節(jié)點(diǎn)

zkclient.getChildren(路徑，是否監(jiān)聽(tīng))
返回的是子節(jié)點(diǎn)的列表

例子：
public void getChildNode() {
        try {
            List<String> children = zkClient.getChildren("/", false);
            for (String node : children) {
                System.out.println(node);
            }
        } catch (KeeperException e) {
            System.out.println("node not exists!!!");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

5、判斷節(jié)點(diǎn)是否存在

 zkclient.exists(path, 是否監(jiān)聽(tīng))
 返回的是節(jié)點(diǎn)的狀態(tài)信息，如果為null，表示節(jié)點(diǎn)不存在

 例子：
 public void nodeExist() {
        //返回的是節(jié)點(diǎn)的狀態(tài)信息，如果為null，表示節(jié)點(diǎn)不存在
        try {
            Stat stat = zkClient.exists("/king", false);
            System.out.println(stat == null ? "沒(méi)有" : "有");
        } catch (KeeperException e) {
            System.out.println("node not exists");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

四、使用zk做分布式鎖實(shí)例

1、maven依賴

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

2、需求
模擬搶購(gòu)秒殺場(chǎng)景，需要給商品數(shù)量加鎖。

3、代碼

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 TestDistributedLock {

    //定義共享資源
    private static int count = 10;

    //用于減除商品
    private static void printCountNumber() {
        System.out.println("***********" + Thread.currentThread().getName() + "**********");
        System.out.println("當(dāng)前值：" + count);
        count--;

        //睡2秒
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("***********" + Thread.currentThread().getName() + "**********");
    }

    public static void main(String[] args) {
        //定義客戶端重試的策略
        RetryPolicy policy = new ExponentialBackoffRetry(1000,  //每次等待的時(shí)間
                10); //最大重試的次數(shù)

        //定義ZK的一個(gè)客戶端
        CuratorFramework client = CuratorFrameworkFactory.builder()
                .connectString("bigdata121:2181")
                .retryPolicy(policy)
                .build();

        //客戶端對(duì)象連接zk
        client.start();
        //創(chuàng)建互斥鎖，其實(shí)就是在zk上創(chuàng)建個(gè)節(jié)點(diǎn)
        final InterProcessMutex lock = new InterProcessMutex(client, "/mylock");

        // 啟動(dòng)10個(gè)線程去訪問(wèn)共享資源
        for (int i = 0; i < 10; i++) {
            new Thread(new Runnable() {

                public void run() {
                    try {
                        //請(qǐng)求得到鎖
                        lock.acquire();
                        //訪問(wèn)共享資源
                        printCountNumber();
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    } finally {
                        //釋放鎖
                        try {
                            lock.release();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            }).start();
        }
    }
}