ZooKeeper學習第三期—Zookeeper命令操作

一、Zookeeper的四字命令

Zookeeper支援某些特定的四字命令字母與其的互動。他們大多數是查詢命令，用來獲取Zookeeper服務的當前狀態及相關資訊。使用者在客戶端可以通過telnet或nc向Zookeeper提交相應的命令。Zookeeper常用的四字命令見下圖所示。

上圖，是Zookeeper四字命令的一個簡單用例。

[[email protected] ~]# echo ruok|nc localhost 2181
 

[[email protected] ~]# zkServer.sh start zoo1.cfg
JMX enabled by default
Using config: /usr/local/zk/bin/../conf/zoo1.cfg
Starting zookeeper ... STARTED
[[email protected] ~]#  zkServer.sh start zoo2.cfg
JMX enabled by default
Using config: /usr/local/zk/bin/../conf/zoo2.cfg
Starting zookeeper ... STARTED
[
 
[email protected] ~]#  zkServer.sh start zoo3.cfg
JMX enabled by default
Using config: /usr/local/zk/bin/../conf/zoo3.cfg
Starting zookeeper ... STARTED
[[email protected] ~]# echo ruok|nc localhost 2181
imok[[email protected] ~]# echo ruok|nc localhost 2182
imok[[email protected] ~]# echo ruok
 
|nc localhost 2183
imok[[email protected] ~]# echo conf|nc localhost 2181
clientPort=2181
dataDir=/usr/local/zk/data_1/version-2
dataLogDir=/usr/local/zk/logs_1/version-2
tickTime=2000
maxClientCnxns=60
minSessionTimeout=4000
maxSessionTimeout=40000
serverId=0
initLimit=10
syncLimit=5
electionAlg=3
electionPort=3387
quorumPort=2287
peerType=0
[[email protected] ~]#

二、Zookeeper的簡單操作

2.1  Zookeeper的shell操作

2.1.1 Zookeeper命令工具

再啟動Zookeeper服務之後，輸入以下命令，連線到Zookeeper服務：

　　　　zkCli.sh -server localhost:2181

執行結果如下所示：

[[email protected] ~]# zkCli.sh -server localhost:2181
Connecting to localhost:2181
2014-10-17 03:35:51,051 [myid:] - INFO  [main:[email protected]100] - Client environment:zookeeper.version=3.4.5-1392090, built on 09/30/2012 17:52 GMT
2014-10-17 03:35:51,055 [myid:] - INFO  [main:[email protected]100] - Client environment:host.name=hadoop
2014-10-17 03:35:51,057 [myid:] - INFO  [main:[email protected]100] - Client environment:java.version=1.6.0_24
2014-10-17 03:35:51,057 [myid:] - INFO  [main:[email protected]100] - Client environment:java.vendor=Sun Microsystems Inc.
2014-10-17 03:35:51,066 [myid:] - INFO  [main:[email protected]100] - Client environment:java.home=/usr/local/jdk/jre
2014-10-17 03:35:51,079 [myid:] - INFO  [main:[email protected]100] - Client environment:java.class.path=/usr/local/zk/bin/../build/classes:/usr/local/zk/bin/../build/lib/*.jar:/usr/local/zk/bin/../lib/slf4j-log4j12-1.6.1.jar:/usr/local/zk/bin/../lib/slf4j-api-1.6.1.jar:/usr/local/zk/bin/../lib/netty-3.2.2.Final.jar:/usr/local/zk/bin/../lib/log4j-1.2.15.jar:/usr/local/zk/bin/../lib/jline-0.9.94.jar:/usr/local/zk/bin/../zookeeper-3.4.5.jar:/usr/local/zk/bin/../src/java/lib/*.jar:/usr/local/zk/bin/../conf:
2014-10-17 03:35:51,083 [myid:] - INFO  [main:[email protected]] - Client environment:java.library.path=/usr/local/jdk/jre/lib/i386/client:/usr/local/jdk/jre/lib/i386:/usr/local/jdk/jre/../lib/i386:/usr/java/packages/lib/i386:/lib:/usr/lib
2014-10-17 03:35:51,084 [myid:] - INFO  [main:[email protected]] - Client environment:java.io.tmpdir=/tmp
2014-10-17 03:35:51,086 [myid:] - INFO  [main:[email protected]] - Client environment:java.compiler=<NA>
2014-10-17 03:35:51,099 [myid:] - INFO  [main:[email protected]] - Client environment:os.name=Linux
2014-10-17 03:35:51,100 [myid:] - INFO  [main:[email protected]] - Client environment:os.arch=i386
2014-10-17 03:35:51,101 [myid:] - INFO  [main:[email protected]] - Client environment:os.version=2.6.32-358.el6.i686
2014-10-17 03:35:51,101 [myid:] - INFO  [main:[email protected]] - Client environment:user.name=root
2014-10-17 03:35:51,102 [myid:] - INFO  [main:[email protected]] - Client environment:user.home=/root
2014-10-17 03:35:51,106 [myid:] - INFO  [main:[email protected]] - Client environment:user.dir=/root
2014-10-17 03:35:51,120 [myid:] - INFO  [main:[email protected]] - Initiating client connection, connectString=localhost:2181 sessionTimeout=30000 [email protected]
Welcome to ZooKeeper!
JLine support is enabled
2014-10-17 03:35:51,233 [myid:] - INFO  [main-SendThread(localhost:2181):[email protected]] - Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (Unable to locate a login configuration)
2014-10-17 03:35:51,247 [myid:] - INFO  [main-SendThread(localhost:2181):[email protected]] - Socket connection established to localhost/127.0.0.1:2181, initiating session
[zk: localhost:2181(CONNECTING) 0] 2014-10-17 03:35:51,290 [myid:] - INFO  [main-SendThread(localhost:2181):[email protected]] - Session establishment complete on server localhost/127.0.0.1:2181, sessionid = 0x491da0e20b0000, negotiated timeout = 30000

WATCHER::

WatchedEvent state:SyncConnected type:None path:null

[zk: localhost:2181(CONNECTED) 0]

View Code

　　連線成功之後，系統會輸出Zookeeper的相關環境及配置資訊，並在螢幕輸出“welcome to Zookeeper！”等資訊。輸入help之後，螢幕會輸出可用的Zookeeper命令，如下圖所示

2.1.2 使用Zookeeper命令的簡單操作步驟

(1) 使用ls命令檢視當前Zookeeper中所包含的內容：ls /

[zk: localhost:2181(CONNECTED) 1] ls /
[zookeeper]
[zk: localhost:2181(CONNECTED) 2]

(2) 建立一個新的Znode節點”zk”，以及和它相關字元，執行命令：create /zk myData

[zk: localhost:2181(CONNECTED) 2] create /zk myData
Created /zk

(3) 再次使用ls命令來檢視現在Zookeeper的中所包含的內容：ls /

[zk: localhost:2181(CONNECTED) 3] ls /
[zk, zookeeper]

此時看到，zk節點已經被建立。　　

(4) 使用get命令來確認第二步中所建立的Znode是否包含我們建立的字串，執行命令：get /zk

[zk: localhost:2181(CONNECTED) 4] get /zk
myData
cZxid = 0x500000006
ctime = Fri Oct 17 03:54:20 PDT 2014
mZxid = 0x500000006
mtime = Fri Oct 17 03:54:20 PDT 2014
pZxid = 0x500000006
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0

(5) 接下來通過set命令來對zk所關聯的字串進行設定，執行命令：set /zk jiang1234

[zk: localhost:2181(CONNECTED) 5] set /zk jiang2014
cZxid = 0x500000006
ctime = Fri Oct 17 03:54:20 PDT 2014
mZxid = 0x500000007
mtime = Fri Oct 17 03:55:50 PDT 2014
pZxid = 0x500000006
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 9
numChildren = 0

(6) 再次使用get命令來檢視，上次修改的內容，執行命令：get /zk

[zk: localhost:2181(CONNECTED) 6] get /zk
jiang2014
cZxid = 0x500000006
ctime = Fri Oct 17 03:54:20 PDT 2014
mZxid = 0x500000007
mtime = Fri Oct 17 03:55:50 PDT 2014
pZxid = 0x500000006
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 9
numChildren = 0

(7) 下面我們將剛才建立的Znode刪除，執行命令：delete /zk

[zk: localhost:2181(CONNECTED) 7] delete /zk

(8) 最後再次使用ls命令檢視Zookeeper中的內容，執行命令：ls /

[zk: localhost:2181(CONNECTED) 8] ls /
[zookeeper]

經過驗證，zk節點已經刪除。

2.2 Zookeeper的api的簡單使用

2.2.1 ZookeeperAPI簡介

Zookeeper API共包含五個包，分別為：

　　（1）org.apache.zookeeper
　　（2）org.apache.zookeeper.data
　　（3）org.apache.zookeeper.server
　　（4）org.apache.zookeeper.server.quorum
　　（5）org.apache.zookeeper.server.upgrade

其中org.apache.zookeeper，包含Zookeeper類，他是我們程式設計時最常用的類檔案。這個類是Zookeeper客戶端的主要類檔案。如果要使用Zookeeper服務，應用程式首先必須建立一個Zookeeper例項，這時就需要使用此類。一旦客戶端和Zookeeper服務建立起了連線，Zookeeper系統將會給次連線會話分配一個ID值，並且客戶端將會週期性的向伺服器端傳送心跳來維持會話連線。只要連線有效，客戶端就可以使用Zookeeper API來做相應處理了。

Zookeeper類提供瞭如下圖所示的幾類主要方法

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