Zookeeper集群搭建（配置详解）

软件环境准备:

Linux服务器一台、三台、五台（2*n+1台）；
Java jdk 1.7；
zookeeper 3.4.6版；

软件安装：

解压jdk、zookeeper文件到指定目录，执行命令tar -zvxf xxxx.tar.gz -C /usr/local/program
配置环境变量，vi /etc/profile

#set enviroment
export JAVA_HOME=/usr/local/program/jdk1.7.0_79
export ZK_HOME=/usr/local/program/zk/zookeeper-3.4.6
export PATH=$JAVA_HOME/bin:$ZK_HOME/bin:$PATH

java -version 命令测试是否成功配置jdk

[root@localhost ~]# java -version
java version "1.7.0_79"
Java(TM) SE Runtime Environment (build 1.7.0_79-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

配置zookeeper；首先建立两个文件夹mkdir /usr/local/program/zk/zkdata ，mkdir /usr/local/program/zk/zkdataLog 
然后执行命令cd /usr/local/program/zk/zookeeper-3.4.6/conf/ 进入配置文件目录，拷贝一份配置文件cp zoo_sample.cfg zoo.cfg改名为zoo.cfg
编辑配置文件修改配置（将端口改大的目的是为了防止冲突）：

# The number of milliseconds of each tick
tickTime=2000
# The number of ticks that the initial
# synchronization phase can take
initLimit=10
# The number of ticks that can pass between
# sending a request and getting an acknowledgement
syncLimit=5
# the directory where the snapshot is stored.
# do not use /tmp for storage, /tmp here is just
# example sakes.
dataDir=/usr/local/program/zk/zkdata
dataLogDir=/usr/local/program/zk/zkdataLog
# the port at which the clients will connect
clientPort=12181
# the maximum number of client connections.
# increase this if you need to handle more clients
#maxClientCnxns=60
#
# Be sure to read the maintenance section of the
# administrator guide before turning on autopurge.
#
# http://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_maintenance #
# The number of snapshots to retain in dataDir
#autopurge.snapRetainCount=3
# Purge task interval in hours
# Set to "0" to disable auto purge feature
#autopurge.purgeInterval=1
server.1=192.168.0.102:12888:13888
server.2=192.168.0.103:12888:13888
server.3=192.168.0.104:12888:13888

进入zkdata目录，执行命令echo “1” > myid创建myid文件并输入值为1
依次在另外两台机器上执行同样的操作，myid的数值依次为2,3
配置成功，执行命令zkServer.sh start分别启动三台机器
执行命令zkServer.sh status查看对应的状态发现出现：zookeeper Error contacting service. It is probably not running错误
执行命令：tail -f zookeeper.out

查看到错误记录：

2016-04-21 06:56:56,242 [myid:1] – WARN  [QuorumPeer[myid=1]/0:0:0:0:0:0:0:0:2181:Follower@89] – Exception when following the leader

java.net.NoRouteToHostException: No route to host

at java.net.PlainSocketImpl.socketConnect(Native Method)

at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)

at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)

at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)

at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)

at java.net.Socket.connect(Socket.java:579)

at org.apache.zookeeper.server.quorum.Learner.connectToLeader(Learner.java:225)

at org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:71)

at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:786)

经验证：防火墙的问题，执行命令service iptables stop关闭防火墙（如要永久关闭防火墙执行命令：chkconfig iptables off）
重启机器，执行命令zkServer.sh status 分别查看每台机器的状态为leader、follower、follower则表明启动成功

配置说明：

作用：
leader：从客户端接收读写请求，响应读写请求，向slaver发送数据
slaver：从leader同步数据，当leader失败时，从新投票选举新的leader

配置详解：
myid:位于快照目录，是用来标识本台机器在集群中的唯一标识
zoo.cfg:
tickTime:是initLimit 和 syncLimit的时间单位（毫秒）
initLimit:集群机器之间的同步时间，比如启动m1，s1在这个时间段内必须都起来
syncLimit：leader与follower之间的通信时间（心跳），超时则说明follower失败

#快照日志的存储路径
dataDir=/usr/local/program/zk/zkdata
#zk事物日志存储目录 (如果不配置zkdataLog那么快照日志和事务日志都将写到dataDir中，严重影响性能)
dataLogDir=/usr/local/program/zk/zkdataLog
# the port at which the clients will connect
#本台机器的端口，默认为2181
clientPort=12181
log4j.properties:
日志文件，zookeeper.out位置bin下面，可以更改

注意：需要定期清理事务日志文件，否则会造成性能下降（crontab）
crontab -l查看当前用户定时任务
crontab -e编辑定时任务
(例：0 0 * * 0 sh /usr/local/program/zk/cleanup.sh)
另外2台机器执行同样的操作

#server.1标识本台机器，通过myid文件指定id=1;ip:机器之间通信端口（默认为2888）:leader选举端口（默认为3888）
server.1=192.168.0.102:12888:13888