ZooKeeper是一个分布式的，开放源码的分布式应用程序协调服务，是Google的Chubby一个开源的实现，是Hadoop和Hbase的重要组件。它是一个为分布式应用提供一致性服务的软件，提供的功能包括：配置维护、域名服务、分布式同步、组服务等。
ZooKeeper的目标就是封装好复杂易出错的关键服务，将简单易用的接口和性能高效、功能稳定的系统提供给用户。
ZooKeeper包含一个简单的原语集提供Java和C的接口。
ZooKeeper代码版本中，提供了分布式独享锁、选举、队列的接口，代码在zookeeper-3.4.3src ecipes。其中分布锁和队列有Java和C两个版本，选举只有Java版本。
主要作用是用来解决分布式应用中经常遇到的一些数据管理问题，如集群管理、统一命名管理、分布式配置管理、分布式消息队列、分布式锁、分布式通知协调
官方网站：https://zookeeper.apache.org/
zookeeper体系结构
zk的集群中有一个Leader，有一个或多个follower，它们之间是相互通信的，然后还存在一个客户端用来访问zk服务器。
服务器端具有fast fail特性，一旦主故障后，会选举从成为新的主，主从模式是目前最常见的模式。
zookeeper名字空间由节点NODE构成,类似于文件系统,其中各个节点相当于目录和文件,通过路径作为唯一标识,与文件系统不同的是,每个节点具有与之对应的数据内容,同时也可以具有子节点,它用来存储协调数据,如状态、配置、位置信息、每个节点存储的数据量很小，KB级别.
watches介绍
zk对节点的增、删、改、查都可以触发监听
watch事件是一次性触发器，当它监视的数据发生变化时，通知设置了该客户端
Zookeeper安装布署
四台服务器
zk-001 10.0.0.8
zk-002 10.0.0.9
zk-003 10.0.0.10
zk-client 10.0.0.100
下载安装JDK环境
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)
下载安装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/
配置环境变量
export ZOOKEEPER_HOME=/usr/local/zookeeper
export PATH=$ZOOKEEPER_HOME/bin:$PATH
source /etc/profile
Zookeeper的配置
三种配置模式
1、伪分布模式
2、完全分布式
3、独立模式
独立模式配置
[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 #心跳检查周期（单位毫秒）
# the directory where the snapshot is stored.
# do not use /tmp for storage, /tmp here is just
# example sakes.
dataDir=/tmp/zookeeper #存放数据目录
# the port at which the clients will connect
clientPort=2181 #供客户端连接的端口
集群模式配置
tickTime=2000
initLimit=10
syncLimit=5
//server.n=host:port1:port2
数字N必须是myid中的值，Myid文件位于dataDIR目录下，只能是一个n值
//port1:leader端口，作为leader时，供follower连接的端口
//port2:选举端口，选举leader时，供follower连接的端口
server.1=s1:2888:3888
server.2=s2:2888:3888
server.3=s3:2888:3888
zk处理集群故障的算法是2n+1,最好在奇数机器数布署，如果同台服务器配置多实例就要注意端口冲突问题，可以写成如下
server.1=s1:2888:3888
server.2=s2:2889:3889
server.3=s3:2887:3887
配置过程如下
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
配置各服务器配置文件
[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
启动服务
[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
查看状态
[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
可以看出已经选举leader出来了，表明配置是正确的
测试leader故障后切换情况
[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这台服务器被选举成新的leader了
Zookeeper客户端四字符指令
conf 配置信息
cons 连接信息
dump 未处理会话节点
envi 环境信息
reqs 未处理请求
stat 统计信息
wchs 服务器watch的详细信息
wchp 列出指定路径下服务器信息
[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客户端命令
通过zkCli.sh 连接服务器
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 ##帮助命令
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 /
#列出目录下内容
[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
#创建目录及数据
Created /root
[zk: zk-002:2181(CONNECTED)5]get /root #获取数据
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是不能一次创建多级节点的
[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]
查看状态
[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
删除目录
[zk: zk-002:2181(CONNECTED) 15] delete /root/s3
[zk: zk-002:2181(CONNECTED) 16] ls /root
[s1, s2]
断开连接
[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
重新连接
由于ZK服务器间的数据是一致的，因此这次我连接其它服务器
[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