ZooKeeper是一個(gè)分布式的，開放源碼的分布式應(yīng)用程序協(xié)調(diào)服務(wù)，是Google的Chubby一個(gè)開源的實(shí)現(xiàn)，是Hadoop和Hbase的重要組件。它是一個(gè)為分布式應(yīng)用提供一致性服務(wù)的軟件，提供的功能包括：配置維護(hù)、域名服務(wù)、分布式同步、組服務(wù)等。

安裝啟動(dòng)

安裝：把zk安裝包上傳到/opt目錄下，并切換到/opt目錄下，執(zhí)行以下指令

(資料圖片僅供參考)

#解壓tar-zxvfzookeeper-3.7.0-bin.tar.gz#重命名mvapache-zookeeper-3.7.0-bin/zookeeper#打開zookeeper根目錄cd/opt/zookeeper#創(chuàng)建一個(gè)數(shù)據(jù)目錄，備用mkdirdata#打開zk的配置目錄cd/opt/zookeeper/conf#copy配置文件，zk啟動(dòng)時(shí)會(huì)加載zoo.cfg文件cpzoo_sample.cfgzoo.cfg#編輯配置文件vimzoo.cfg#修改dataDir參數(shù)為之前創(chuàng)建的數(shù)據(jù)目錄：/opt/zookeeper/data#切換到bin目錄cd/opt/zookeeper/bin#啟動(dòng)./zkServer.shstart./zkServer.shstatus#查看啟動(dòng)狀態(tài)./zkServer.shstop#停止./zkServer.shrestart#重啟./zkCli.sh#查看zk客戶端

如下，說(shuō)明啟動(dòng)成功：

相關(guān)概念

Zookeeper提供一個(gè)多層級(jí)的節(jié)點(diǎn)命名空間（節(jié)點(diǎn)稱為znode），每個(gè)節(jié)點(diǎn)都用一個(gè)以斜杠（/）分隔的路徑表示，而且每個(gè)節(jié)點(diǎn)都有父節(jié)點(diǎn)（根節(jié)點(diǎn)除外），非常類似于文件系統(tǒng)。并且每個(gè)節(jié)點(diǎn)都是唯一的。

znode節(jié)點(diǎn)有四種類型：

PERSISTENT：永久節(jié)點(diǎn)?？蛻舳伺czookeeper斷開連接后，該節(jié)點(diǎn)依舊存在

EPHEMERAL：臨時(shí)節(jié)點(diǎn)。客戶端與zookeeper斷開連接后，該節(jié)點(diǎn)被刪除

PERSISTENT_SEQUENTIAL：永久節(jié)點(diǎn)、序列化?？蛻舳伺czookeeper斷開連接后，該節(jié)點(diǎn)依舊存在，只是Zookeeper給該節(jié)點(diǎn)名稱進(jìn)行順序編號(hào)

EPHEMERAL_SEQUENTIAL：臨時(shí)節(jié)點(diǎn)、序列化。客戶端與zookeeper斷開連接后，該節(jié)點(diǎn)被刪除，只是Zookeeper給該節(jié)點(diǎn)名稱進(jìn)行順序編號(hào)

操作節(jié)點(diǎn)

創(chuàng)建這四種節(jié)點(diǎn)：

[zk:localhost:2181(CONNECTED)0]create/aatest#創(chuàng)建持久化節(jié)點(diǎn)Created/aa[zk:localhost:2181(CONNECTED)1]create-s/bbtest#創(chuàng)建持久序列化節(jié)點(diǎn)Created/bb0000000001[zk:localhost:2181(CONNECTED)2]create-e/cctest#創(chuàng)建臨時(shí)節(jié)點(diǎn)Created/cc[zk:localhost:2181(CONNECTED)3]create-e-s/ddtest#創(chuàng)建臨時(shí)序列化節(jié)點(diǎn)Created/dd0000000003[zk:localhost:2181(CONNECTED)4]ls/#查看某個(gè)節(jié)點(diǎn)下的子節(jié)點(diǎn)[aa,bb0000000001,cc,dd0000000003,zookeeper][zk:localhost:2181(CONNECTED)5]stat/#查看某個(gè)節(jié)點(diǎn)的狀態(tài)cZxid=0x0ctime=ThuJan0108:00:00CST1970mZxid=0x0mtime=ThuJan0108:00:00CST1970pZxid=0x5cversion=3dataVersion=0aclVersion=0ephemeralOwner=0x0dataLength=0numChildren=5[zk:localhost:2181(CONNECTED)6]get/aa#查看某個(gè)節(jié)點(diǎn)的內(nèi)容test[zk:localhost:2181(CONNECTED)11]delete/aa#刪除某個(gè)節(jié)點(diǎn)[zk:localhost:2181(CONNECTED)7]ls/#再次查看[bb0000000001,cc,dd0000000003,zookeeper]

事件監(jiān)聽

在讀取數(shù)據(jù)時(shí)，我們可以同時(shí)對(duì)節(jié)點(diǎn)設(shè)置事件監(jiān)聽，當(dāng)節(jié)點(diǎn)數(shù)據(jù)或結(jié)構(gòu)變化時(shí)，zookeeper會(huì)通知客戶端。當(dāng)前zookeeper針對(duì)節(jié)點(diǎn)的監(jiān)聽有如下四種事件：

節(jié)點(diǎn)創(chuàng)建：stat-w/xx

當(dāng)/xx節(jié)點(diǎn)創(chuàng)建時(shí)：NodeCreated

節(jié)點(diǎn)刪除：stat-w/xx

當(dāng)/xx節(jié)點(diǎn)刪除時(shí)：NodeDeleted

節(jié)點(diǎn)數(shù)據(jù)修改：get-w/xx

當(dāng)/xx節(jié)點(diǎn)數(shù)據(jù)發(fā)生變化時(shí)：NodeDataChanged

子節(jié)點(diǎn)變更：ls-w/xx

當(dāng)/xx節(jié)點(diǎn)的子節(jié)點(diǎn)創(chuàng)建或者刪除時(shí)：NodeChildChanged

java客戶端

ZooKeeper的java客戶端有：原生客戶端、ZkClient、Curator框架（類似于redisson，有很多功能性封裝）。

引入依賴

org.apache.zookeeperzookeeper3.7.0

常用api及其方法

publicclassZkTest{publicstaticvoidmain(String[]args)throwsKeeperException,InterruptedException{//獲取zookeeper鏈接CountDownLatchcountDownLatch=newCountDownLatch(1);ZooKeeperzooKeeper=null;try{zooKeeper=newZooKeeper("172.16.116.100:2181",30000,newWatcher{@Overridepublicvoidprocess(WatchedEventevent){if(Event.KeeperState.SyncConnected.equals(event.getState)&&Event.EventType.None.equals(event.getType)){System.out.println("獲取鏈接成功。。。。。。"+event);countDownLatch.countDown;}}});countDownLatch.await;}catch(Exceptione){e.printStackTrace;}//創(chuàng)建一個(gè)節(jié)點(diǎn)，1-節(jié)點(diǎn)路徑2-節(jié)點(diǎn)內(nèi)容3-節(jié)點(diǎn)的訪問(wèn)權(quán)限4-節(jié)點(diǎn)類型//OPEN_ACL_UNSAFE：任何人可以操作該節(jié)點(diǎn)//CREATOR_ALL_ACL：創(chuàng)建者擁有所有訪問(wèn)權(quán)限//READ_ACL_UNSAFE:任何人都可以讀取該節(jié)點(diǎn)//zooKeeper.create("/zktest/aa","haha~~".getBytes,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);zooKeeper.create("/test","haha~~".getBytes,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL);//zooKeeper.create("/zktest/cc","haha~~".getBytes,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT_SEQUENTIAL);//zooKeeper.create("/zktest/dd","haha~~".getBytes,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);//zooKeeper.create("/zktest/dd","haha~~".getBytes,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);//zooKeeper.create("/zktest/dd","haha~~".getBytes,ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);//判斷節(jié)點(diǎn)是否存在Statstat=zooKeeper.exists("/test",true);if(stat!=null){System.out.println("當(dāng)前節(jié)點(diǎn)存在！"+stat.getVersion);}else{System.out.println("當(dāng)前節(jié)點(diǎn)不存在！");}//判斷節(jié)點(diǎn)是否存在，同時(shí)添加監(jiān)聽zooKeeper.exists("/test",event->{});//獲取一個(gè)節(jié)點(diǎn)的數(shù)據(jù)byte[]data=zooKeeper.getData("/zktest/ss0000000001",false,null);System.out.println(newString(data));//查詢一個(gè)節(jié)點(diǎn)的所有子節(jié)點(diǎn)Listchildren=zooKeeper.getChildren("/test",false);System.out.println(children);//更新zooKeeper.setData("/test","wawa...".getBytes,stat.getVersion);//刪除一個(gè)節(jié)點(diǎn)//zooKeeper.delete("/test",-1);if(zooKeeper!=null){zooKeeper.close;}}}

關(guān)鍵詞： 事件監(jiān)聽 協(xié)調(diào)服務(wù)