zookeeper的介紹、部署、常用命令以及API

Zookeeper描述：
Zookeeper是一個開源的分佈式的，爲分佈式應用提供協調服務的Apache項目。起作用有點難描述，在Hadoop生態裏充當潤滑液的作用。zookeeper=文件系統+通知監聽機制。它的文件系統和普通的文件系統有點差別，它的父節點和葉子節點都能存數據；它的監聽通知機制就是：zookeeper分爲客戶端和服務端，客戶端會監聽服務器列表，有服務器下線或者宕機，zookeeper就會作出響應。
話不多說直接上搭建過程：
先去官網下載zookeeper：https://zookeeper.apache.org/
我下載的是3.4.10，然後把壓縮包傳到linux裏，我放的路徑是/opt/software/裏面。前提是要把jdk安裝好。
1.解壓
在/opt/software下解壓，解壓到/opt/module/下，命令爲如下：tar -zxvf zookeeper-3.4.10.tar.gz -C /opt/module/
2.修改配置
（1）將/opt/module/zookeeper-3.4.10/conf這個路徑下的zoo_sample.cfg修改爲zoo.cfg；
mv zoo_sample.cfg zoo.cfg
（2）打開zoo.cfg文件，修改dataDir路徑：
vim zoo.cfg
修改如下內容：
dataDir=/opt/module/zookeeper-3.4.10/zkData
添加一下內容：
server.1=hadoop01:2888:3888
server.2=hadoop02:2888:3888
server.3=hadoop03:2888:3888
hadoop0x是我的三臺虛擬機的主機名，大家配置的時候要修改成自己的。
在/opt/module/zookeeper-3.4.10/zkData目錄下創建一個myid的文件
touch myid
然後把server的編號寫上，例如我現在在hadoop01上配置，通過剛配的文件可以看到，我的hadoop01對應的是server.1，所以在myid裏面要寫上1，等下配置hadoop02的時候就要寫2，以此類推。
（3）在/opt/module/zookeeper-3.4.10/這個目錄上創建zkData文件夾
mkdir zkData
3.zookeeper命令
配置好上述就可以啓動zookeeper了，在zookeeper目錄下：
bin/zkServer.sh start
就可以啓動了，如果想要在哪都可以直接啓動zookeeper就要把zookeeper的bin目錄寫入環境變量即：
把export ZOOKEEPER_HOME=/opt/module/zookeeper-3.4.10/bin寫入到/etc/profile裏即可。
啓動後運行jps就能看到QuorumPeerMain進程，這個就是zookeeper的進程。
（1）查看狀態：
bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/…/conf/zoo.cfg
Mode: standalone
（2）啓動客戶端：
bin/zkCli.sh
（3）退出客戶端：
quit
（4）停止Zookeeper
bin/zkServer.sh stop
接下來就可以把解壓好的zookeeper分發到集羣的其他機器上了，用以下命令：
rsync -av /opt/module/zookeeper-3.4.10 hadoop02:/opt/module
發到其他集羣上後要記得修改myid文件還有配置zookeeper的環境變量，hadoop03亦是如此。
zookeeper客戶端程勇命令操作

命令基本語法	功能描述
help	顯示所有操作命令
ls path [watch]	使用 ls 命令來查看當前znode中所包含的內容
ls2 path [watch]	ls2 path [watch]
create	普通創建-s 含有序列-e 臨時（重啓或者超時消失）
get path [watch]	獲得節點的值
set	設置節點的具體值
stat	查看節點狀態
delete	刪除節點
rmr	遞歸刪除節點

1．啓動客戶端
bin/zkCli.sh
2．顯示所有操作命令
[zk: localhost:2181(CONNECTED) 1] help
3．查看當前znode中所包含的內容
[zk: localhost:2181(CONNECTED) 0] ls /
[zookeeper]
4．查看當前節點詳細數據
[zk: localhost:2181(CONNECTED) 1] ls2 /
[zookeeper]
cZxid = 0x0
ctime = Thu Jan 01 08:00:00 CST 1970
mZxid = 0x0
mtime = Thu Jan 01 08:00:00 CST 1970
pZxid = 0x0
cversion = -1
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 0
numChildren = 1
5．分別創建2個普通節點
[zk: localhost:2181(CONNECTED) 3] create /sanguo “jinlian”
Created /sanguo
[zk: localhost:2181(CONNECTED) 4] create /sanguo/shuguo “liubei”
Created /sanguo/shuguo
6．獲得節點的值
[zk: localhost:2181(CONNECTED) 5] get /sanguo
jinlian
cZxid = 0x100000003
ctime = Wed Aug 29 00:03:23 CST 2018
mZxid = 0x100000003
mtime = Wed Aug 29 00:03:23 CST 2018
pZxid = 0x100000004
cversion = 1
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 7
numChildren = 1
[zk: localhost:2181(CONNECTED) 6]
[zk: localhost:2181(CONNECTED) 6] get /sanguo/shuguo
liubei
cZxid = 0x100000004
ctime = Wed Aug 29 00:04:35 CST 2018
mZxid = 0x100000004
mtime = Wed Aug 29 00:04:35 CST 2018
pZxid = 0x100000004
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0
7．創建短暫節點
[zk: localhost:2181(CONNECTED) 7] create -e /sanguo/wuguo “zhouyu”
Created /sanguo/wuguo
（1）在當前客戶端是能查看到的
[zk: localhost:2181(CONNECTED) 3] ls /sanguo
[wuguo, shuguo]
（2）退出當前客戶端然後再重啓客戶端
[zk: localhost:2181(CONNECTED) 12] quit
bin/zkCli.sh
（3）再次查看根目錄下短暫節點已經刪除
[zk: localhost:2181(CONNECTED) 0] ls /sanguo
[shuguo]
8．創建帶序號的節點
（1）先創建一個普通的根節點/sanguo/weiguo
[zk: localhost:2181(CONNECTED) 1] create /sanguo/weiguo “caocao”
Created /sanguo/weiguo
（2）創建帶序號的節點
[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
如果原來沒有序號節點，序號從0開始依次遞增。如果原節點下已有2個節點，則再排序時從2開始，以此類推。
9．修改節點數據值
[zk: localhost:2181(CONNECTED) 6] set /sanguo/weiguo “simayi”
10．節點的值變化監聽
（1）在hadoop104主機上註冊監聽/sanguo節點數據變化
[zk: localhost:2181(CONNECTED) 26] [zk: localhost:2181(CONNECTED) 8] get /sanguo watch
（2）在hadoop103主機上修改/sanguo節點的數據
[zk: localhost:2181(CONNECTED) 1] set /sanguo “xisi”
（3）觀察hadoop104主機收到數據變化的監聽
WATCHER::
WatchedEvent state:SyncConnected type:NodeDataChanged path:/sanguo
11．節點的子節點變化監聽（路徑變化）
（1）在hadoop104主機上註冊監聽/sanguo節點的子節點變化
[zk: localhost:2181(CONNECTED) 1] ls /sanguo watch
[aa0000000001, server101]
（2）在hadoop103主機/sanguo節點上創建子節點
[zk: localhost:2181(CONNECTED) 2] create /sanguo/jin “simayi”
Created /sanguo/jin
（3）觀察hadoop104主機收到子節點變化的監聽
WATCHER::
WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/sanguo
12．刪除節點
[zk: localhost:2181(CONNECTED) 4] delete /sanguo/jin
13．遞歸刪除節點
[zk: localhost:2181(CONNECTED) 15] rmr /sanguo/shuguo
14．查看節點狀態
[zk: localhost:2181(CONNECTED) 17] stat /sanguo
cZxid = 0x100000003
ctime = Wed Aug 29 00:03:23 CST 2018
mZxid = 0x100000011
mtime = Wed Aug 29 00:21:23 CST 2018
pZxid = 0x100000014
cversion = 9
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 4
numChildren = 1

zookeeper API應用

IDEA環境搭建（eclipse搭建方法也差不多）
1．創建一個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．拷貝log4j.properties文件到項目根目錄
需要在項目的src/main/resources目錄下，新建一個文件，命名爲“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

以下代碼包含了zookeeper的一些增刪改查API方法：

package cn.edu.lingnan.zookeeper;

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 zkClient {

    private ZooKeeper zkCli;
    private static final String CONNECT_STRING = "192.168.218.130:2181,192.168.218.131:2181,192.168.218.132:2181";
    private static final int SESSION_TIMEOUT = 2000;

    //回調函數會在節點發生變化的時候通知主線程
    @Before
    public void before() throws IOException {
        zkCli = new ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, new Watcher() {
            public void process(WatchedEvent event) {
                System.out.println("默認回調函數");
            }
        });
    }

    //相當於zookeeper的ls path命令
    @Test
    public void ls() throws KeeperException, InterruptedException {
        List<String> children = zkCli.getChildren("/", true);
        System.out.println("================================");
        for (String child : children) {
            System.out.println(child);
        }
        System.out.println("================================");
        //讓主線程休眠，讓程序一直等待回調函數的通知
        Thread.sleep(Long.MAX_VALUE);
    }

    //相當於zookeeper的create命令
    @Test
    public void create() throws KeeperException, InterruptedException {
        //最後一個參數代表創建的節點是臨時還是永久，有序還是無序
        String s = zkCli.create("/Idea", "Idea2019".getBytes(),
                ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(s);
        Thread.sleep(Long.MAX_VALUE);
    }

    //相當於zookeeper的get命令
    @Test
    public void get() throws KeeperException, InterruptedException {
        byte[] data = zkCli.getData("/test0", true, new Stat());
        String s = new String(data);
        System.out.println(s);
    }

    //相當於zookeeper的set命令
    @Test
    public void set() throws KeeperException, InterruptedException {
        //最後一個參數表示要修改的版本號，在不知道版本號的時候可以用以下代碼獲得
        /*
            Stat exit = zkCli.exists("/test0", false);
            exit.getVersion();
         */
        Stat stat = zkCli.setData("/test0", "4321".getBytes(), 0);
        byte[] data = zkCli.getData("/test0", true, new Stat());
        String s = new String(data);
        System.out.println(s);
    }

    //相當於zookeeper的stat命令
    @Test
    public void stat() throws KeeperException, InterruptedException {
        Stat exit = zkCli.exists("/test0", false);
        exit.getVersion();
        if(exit == null){
            System.out.println("節點不存在！");
        }else{
            System.out.println(exit.getDataLength());
        }
    }

    @Test
    public void delete() throws KeeperException, InterruptedException {
        Stat exit = zkCli.exists("/test0", false);
        if(exit != null)
            zkCli.delete("/test0",exit.getVersion());

    }

    public void register() throws KeeperException, InterruptedException{
        byte[] data = zkCli.getData("/test0", new Watcher() {
            public void process(WatchedEvent event) {
                try {
                    register();
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },null);
        System.out.println(new String(data));
    }

    //循環註冊，由於zookeeper註冊一次只監聽一次
    @Test
    public void testregister(){
        try {
            register();
            Thread.sleep(Long.MAX_VALUE);
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}