ZooKeeper是一個分佈式的，開放源碼的分佈式應用程序協調服務，是Google的Chubby一個開源的實現，是Hadoop和Hbase的重要組件。它是一個爲分佈式應用提供一致性服務的軟件，提供的功能包括：配置維護、域名服務、分佈式同步、組服務等。
ZooKeeper的目標就是封裝好複雜易出錯的關鍵服務，將簡單易用的接口和性能高效、功能穩定的系統提供給用戶。
ZooKeeper包含一個簡單的原語集提供Java和C的接口。
ZooKeeper代碼版本中，提供了分佈式獨享鎖、選舉、隊列的接口，代碼在zookeeper-3.4.3\src\recipes。其中分佈鎖和隊列有Java和C兩個版本，選舉只有Java版本。
主要作用是用來解決分佈式應用中經常遇到的一些數據管理問題，如集羣管理、統一命名管理、分佈式配置管理、分佈式消息隊列、分佈式鎖、分佈式通知協調
官方網站：https://zookeeper.apache.org/
zookeeper體系結構zk的集羣中有一個Leader，有一個或多個follower，它們之間是相互通信的，然後還存在一個客戶端用來訪問zk服務器。
服務器端具有fast fail特性，一旦主故障後，會選舉從成爲新的主，主從模式是目前最常見的模式。
zookeeper名字空間由節點NODE構成,類似於文件系統,其中各個節點相當於目錄和文件,通過路徑作爲唯一標識,與文件系統不同的是,每個節點具有與之對應的數據內容,同時也可以具有子節點,它用來存儲協調數據,如狀態、配置、位置信息、每個節點存儲的數據量很小，KB級別.
watches介紹
zk對節點的增、刪、改、查都可以觸發監聽
watch事件是一次性觸發器，當它監視的數據發生變化時，通知設置了該客戶端
Zookeeper安裝佈署四臺服務器
zk-001 10.0.0.8
zk-002 10.0.0.9
zk-003 10.0.0.10
zk-client 10.0.0.100
下載安裝JDK環境
tar zxf jdk-8u60-linux-x64.tar.gz
mv jdk1.8.0_60 /usr/local/jdk
export JAVA_HOME=/usr/local/jdk
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export PATH=$JAVA_HOME/bin:$PATH
source /etc/profile
java -version
[root@zk-001 ~]# java -version
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)
下載安裝zookeeper
wget http://www.apache.org/dist/zookeeper/zookeeper-3.4.6/zookeeper-3.4.6.tar.gz
tar zxf zookeeper-3.4.6.tar.gz
mv zookeeper-3.4.6 /usr/local/zookeeper
[root@zk-001 ~]# cd /usr/local/zookeeper/
配置環境變量
export ZOOKEEPER_HOME=/usr/local/zookeeper
export PATH=$ZOOKEEPER_HOME/bin:$PATH
source /etc/profile
Zookeeper的配置三種配置模式
1、僞分佈模式
2、完全分佈式
3、獨立模式
獨立模式配置
[root@zk-001 zookeeper]# cd conf/
[root@zk-001 conf]# ll
total 12
-rw-rw-r-- 1 1000 1000 535 Feb 20 2014 configuration.xsl
-rw-rw-r-- 1 1000 1000 2161 Feb 20 2014 log4j.properties
-rw-rw-r-- 1 1000 1000 922 Feb 20 2014 zoo_sample.cfg
[root@zk-001 conf]# cp zoo_sample.cfg zoo.cfg
[root@zk-001 conf]#vim zoo.cfg
# The number of milliseconds of each tick
tickTime=2000 #心跳檢查週期（單位毫秒）
# the directory where the snapshot is stored.
# do not use /tmp for storage, /tmp here is just
# example sakes.
dataDir=/tmp/zookeeper #存放數據目錄
# the port at which the clients will connect
clientPort=2181 #供客戶端連接的端口
集羣模式配置
tickTime=2000
initLimit=10
syncLimit=5
//server.n=host:port1:port2
數字N必須是myid中的值，Myid文件位於dataDIR目錄下，只能是一個n值
//port1:leader端口，作爲leader時，供follower連接的端口
//port2:選舉端口，選舉leader時，供follower連接的端口
server.1=s1:2888:3888
server.2=s2:2888:3888
server.3=s3:2888:3888
zk處理集羣故障的算法是2n+1,最好在奇數機器數佈署，如果同臺服務器配置多實例就要注意端口衝突問題，可以寫成如下
server.1=s1:2888:3888
server.2=s2:2889:3889
server.3=s3:2887:3887
配置過程如下
配置hosts文件
vim /etc/hosts
10.0.0.8 zk-001
10.0.0.9 zk-002
10.0.0.10 zk-003
配置各服務器配置文件
[root@zk-001 conf]# mkdir /tmp/zookeeper
[root@zk-001 conf]# cd /tmp/zookeeper/
[root@zk-001 zookeeper]# echo 8 >myid
[root@zk-001 conf]# egrep -v "^#|^$" zoo.cfg
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/tmp/zookeeper
clientPort=2181
server.8=zk-001:2888:3888
server.9=zk-002:2888:3888
server.10=zk-003:2888:3888
[root@zk-002 ~]# mkdir /tmp/zookeeper
[root@zk-002 ~]# cd /tmp/zookeeper/
[root@zk-002 zookeeper]# echo 9 >myid
[root@zk-002 zookeeper]# ll
total 4
-rw-r--r-- 1 root root 2 May 13 15:51 myid
[root@zk-002 zookeeper]# cd /usr/local/zookeeper/conf/
[root@zk-002 conf]# cp zoo_sample.cfg zoo.cfg
[root@zk-002 conf]# vim zoo.cfg
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/tmp/zookeeper
clientPort=2181
server.8=zk-001:2888:3888
server.9=zk-002:2888:3888
server.10=zk-003:2888:3888
[root@zk-003 ~]# mkdir /tmp/zookeeper
[root@zk-003 ~]# cd /tmp/zookeeper/
[root@zk-003 zookeeper]# echo 10 >myid
[root@zk-003 zookeeper]# cd /usr/local/zookeeper/conf/
[root@zk-003 conf]# cp zoo_sample.cfg zoo.cfg
[root@zk-003 conf]# vim zoo.cfg
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/tmp/zookeeper
clientPort=2181
server.8=zk-001:2888:3888
server.9=zk-002:2888:3888
server.10=zk-003:2888:3888
啓動服務
[root@zk-001 bin]# zkServer.sh start
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@zk-002 bin]# zkServer.sh start
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@zk-003 bin]# zkServer.sh start
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
查看狀態
[root@zk-001 conf]# zkServer.sh status
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: follower
[root@zk-002 conf]# zkServer.sh status
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: follower
[root@zk-003 conf]# zkServer.sh status
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: leader
可以看出已經選舉leader出來了，表明配置是正確的
測試leader故障後切換情況
[root@zk-003 conf]# jps
2694 Jps
2430 QuorumPeerMain
[root@zk-003 conf]# kill 2430
[root@zk-003 conf]# jps
2724 Jps
[root@zk-002 conf]# zkServer.sh status
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: follower
[root@zk-001 conf]# zkServer.sh status
JMX enabled by default
Using config: /usr/local/zookeeper/bin/../conf/zoo.cfg
Mode: leader
可以看出zk-001這臺服務器被選舉成新的leader了
Zookeeper客戶端四字符指令
conf 配置信息
cons 連接信息
dump 未處理會話節點
envi 環境信息
reqs 未處理請求
stat 統計信息
wchs 服務器watch的詳細信息
wchp 列出指定路徑下服務器信息
[root@zk-003 ~]# echo conf | nc 10.0.0.8 2181
clientPort=2181
dataDir=/tmp/zookeeper/version-2
dataLogDir=/tmp/zookeeper/version-2
tickTime=2000
maxClientCnxns=60
minSessionTimeout=4000
maxSessionTimeout=40000
serverId=8
initLimit=10
syncLimit=5
electionAlg=3
electionPort=3888
quorumPort=2888
peerType=0
[root@zk-003 ~]# echo envi | nc 10.0.0.8 2181
Environment:
zookeeper.version=3.4.6-1569965, built on 02/20/2014 09:09 GMT
host.name=zk-001
java.version=1.8.0_121
java.vendor=Oracle Corporation
java.home=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.121-0.b13.el6_8.x86_64/jre
java.class.path=/usr/local/zookeeper/bin/../build/classes:/usr/local/zookeeper/bin/../build/lib/*.jar:/usr/local/zookeeper/bin/../lib/slf4j-log4j12-1.6.1.jar:/usr/local/zookeeper/bin/../lib/slf4j-api-1.6.1.jar:/usr/local/zookeeper/bin/../lib/netty-3.7.0.Final.jar:/usr/local/zookeeper/bin/../lib/log4j-1.2.16.jar:/usr/local/zookeeper/bin/../lib/jline-0.9.94.jar:/usr/local/zookeeper/bin/../zookeeper-3.4.6.jar:/usr/local/zookeeper/bin/../src/java/lib/*.jar:/usr/local/zookeeper/bin/../conf:
java.library.path=/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
java.io.tmpdir=/tmp
java.compiler=<NA>
os.name=Linux
os.arch=amd64
os.version=2.6.32-504.el6.x86_64
user.name=root
user.home=/root
user.dir=/usr/local/zookeeper/conf
[root@zk-003 ~]# echo stat | nc 10.0.0.8 2181
Zookeeper version: 3.4.6-1569965, built on 02/20/2014 09:09 GMT
Clients:
/10.0.0.10:41192[0](queued=0,recved=1,sent=0)
Latency min/avg/max: 0/0/0
Received: 4
Sent: 3
Connections: 1
Outstanding: 0
Zxid: 0x200000000
Mode: leader
Node count: 4
Zookeeper客戶端命令通過zkCli.sh 連接服務器
zkCli.sh -server zk-001:2181
-server 10.0.0.9:2181
[root@zk-001 ~]# zkCli.sh -server zk-002:2181
Connecting to zk-002:2181
WATCHER::
WatchedEvent state:SyncConnected type:None path:null
[zk: zk-002:2181(CONNECTED) 0] h ##幫助命令
ZooKeeper -server host:port cmd args
stat path [watch]
set path data [version]
ls path [watch]
delquota [-n|-b] path
ls2 path [watch]
setAcl path acl
setquota -n|-b val path
history
redo cmdno
printwatches on|off
delete path [version]
sync path
listquota path
rmr path
get path [watch]
create [-s] [-e] path data acl
addauth scheme auth
quit
getAcl path
close
connect host:port
[zk: zk-002:2181(CONNECTED) 1] ls /
#列出目錄下內容
[zookeeper]
[zk: zk-002:2181(CONNECTED) 2] ls /zookeeper
[quota]
[zk: zk-002:2181(CONNECTED) 3] ls /zookeeper/quota
[]
[zk: zk-002:2181(CONNECTED) 4] create /root testfile
#創建目錄及數據
Created /root
[zk: zk-002:2181(CONNECTED)5]get /root #獲取數據
testfile
cZxid = 0x200000002
ctime = Sat May 13 20:09:52 CST 2017
mZxid = 0x200000002
mtime = Sat May 13 20:09:52 CST 2017
pZxid = 0x200000002
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 8
numChildren = 0
[zk: zk-002:2181(CONNECTED) 6] set /root testfile-001
cZxid = 0x200000002
ctime = Sat May 13 20:09:52 CST 2017
mZxid = 0x200000003
mtime = Sat May 13 21:04:17 CST 2017
pZxid = 0x200000002
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 0
需要注意的是ZK是不能一次創建多級節點的
[zk: zk-002:2181(CONNECTED) 7] create /root/s1/s1-1
[zk: zk-002:2181(CONNECTED) 8] ls /root #提示是空
[]
[zk: zk-002:2181(CONNECTED) 9] create /root/s1 s1-data
Created /root/s1
[zk: zk-002:2181(CONNECTED) 10] create /root/s2 s2-data
Created /root/s2
[zk: zk-002:2181(CONNECTED) 11] create /root/s3 s3-data
Created /root/s3
[zk: zk-002:2181(CONNECTED) 13] ls /root
[s3, s1, s2]
查看狀態
[zk: zk-002:2181(CONNECTED) 14] stat /root
cZxid = 0x200000002
ctime = Sat May 13 20:09:52 CST 2017
mZxid = 0x200000003
mtime = Sat May 13 21:04:17 CST 2017
pZxid = 0x200000006
cversion = 3
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 3
刪除目錄
[zk: zk-002:2181(CONNECTED) 15] delete /root/s3
[zk: zk-002:2181(CONNECTED) 16] ls /root
[s1, s2]
斷開連接
[zk: zk-002:2181(CONNECTED) 17] close
2017-05-13 21:13:00,603 [myid:] - INFO[main:ZooKeeper@684] - Session: 0x95c0122efa50000 closed
2017-05-13 21:13:00,604 [myid:] - INFO[main-EventThread:ClientCnxn$EventThread@512] - EventThread shut down
重新連接
由於ZK服務器間的數據是一致的，因此這次我連接其它服務器
[zk: zk-002:2181(CLOSED) 18] connect zk-001:2181
[zk: zk-001:2181(CONNECTED) 19] get /root
testfile-001
cZxid = 0x200000002
ctime = Sat May 13 20:09:52 CST 2017
mZxid = 0x200000003
mtime = Sat May 13 21:04:17 CST 2017
pZxid = 0x200000007
cversion = 4
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 2
[zk: zk-001:2181(CONNECTED) 20] get /root/s1
s1-data
cZxid = 0x200000004
ctime = Sat May 13 21:07:42 CST 2017
mZxid = 0x200000004
mtime = Sat May 13 21:07:42 CST 2017
pZxid = 0x200000004
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 7
numChildren = 0
