基于centos8搭建zookeeper集群

【README】本文基于centos8 搭建

1，其他linux版本，命令可能不同；

2，集群包括3个节点，如下（因为采用NAT模型进行网络连接，需要让windows和linux机器在同一个网段）：

centos01: 192.168.163.201
centos02: 192.168.163.202
centos02: 192.168.163.203

【1】软件准备

1、远程文件传输软件

window 与 centos 文件传输， sz， rz
yum -y install lrzsz
yum -y install vim
yum -y install scp

yum -y install rsync 远程同步文件

2、安装java
vim /etc/profile
# JVM ENV
JAVA_HOME=/usr/local/java/jdk1.8
JRE_HOME=$JAVA_HOME/jre
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME CLASSPATH PATH JRE_HOME

source /etc/profile 更新

java -version

【2】搭建单机模式的zk

步骤1：下载 zookeeper 框架包，本文使用 zookeeper-3.4.10 , https://archive.apache.org/dist/zookeeper/zookeeper-3.4.10/zookeeper-3.4.10.tar.gz

[root@localhost module]# ls
zookeeper-3.4.10.tar.gz

步骤2：解压，位置在 /opt/module

tar -zxvf zookeeper-3.4.10.tar.gz
[root@localhost module]# ls
zookeeper-3.4.10  zookeeper-3.4.10.tar.gz
[root@localhost module]# pwd
/opt/module
[root@localhost module]# cd zookeeper-3.4.10
[root@localhost zookeeper-3.4.10]# pwd
/opt/module/zookeeper-3.4.10

步骤3：修改 zookeeper 配置文件

[root@localhost zookeeper-3.4.10]# cd conf
[root@localhost conf]# ls
configuration.xsl  log4j.properties  zoo_sample.cfg
[root@localhost conf]# cp zoo_sample.cfg zoo.cfg
[root@localhost conf]# vim zoo.cfg

设置zoo.cfg 如下，修改 dataDir=/opt/module/zookeeper-3.4.10/zkdata zkdata为自定义文件夹

-- zoo.cfg[root@localhost conf]# cat zoo.cfg
# 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=/opt/module/zookeeper-3.4.10/zkdata
# the port at which the clients will connect
clientPort=2181
# 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

步骤4：新建 /opt/module/zookeeper-3.4.10/zkdata 文件夹

[root@localhost zookeeper-3.4.10]# pwd
/opt/module/zookeeper-3.4.10
[root@localhost zookeeper-3.4.10]# mkdir zkdata

步骤5：启动zk，并查看zk状态

[root@localhost zookeeper-3.4.10]# bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@localhost zookeeper-3.4.10]#
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: standalone

standalone 为单机模式；

提醒：这里可能报错 Error contacting service. It is probably not running.

解决方法1： 关闭防火墙
查看防火墙状态：firewall-cmd --state
关闭防火墙：systemctl stop firewalld.service解决方法2： https://blog.csdn.net/PacosonSWJTU/article/details/111260961
懂的查看  zk 目录下的  zookeeper.out 日志文件；

步骤6：启动zk客户端，并退出（quit）

[root@localhost zookeeper-3.4.10]# bin/zkCli.sh
Connecting to localhost:2181
Welcome to ZooKeeper!
......
WATCHER::WatchedEvent state:SyncConnected type:None path:null
[zk: localhost:2181(CONNECTED) 0]
[zk: localhost:2181(CONNECTED) 0] ls /
[zookeeper][zk: localhost:2181(CONNECTED) 1] quit
Quitting...
2020-12-20 03:42:33,745 [myid:] - INFO  [main:ZooKeeper@684] - Session: 0x1767c83c15e0000 closed
2020-12-20 03:42:33,747 [myid:] - INFO  [main-EventThread:ClientCnxn$EventThread@519] - EventThread shut down for session: 0x1767c83c15e0000
[root@localhost zookeeper-3.4.10]#

步骤7：停止zk线程（或有）

[root@localhost zookeeper-3.4.10]# bin/zkServer.sh stop
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Stopping zookeeper ... STOPPED

补充：zoo.cfg 配置解析

序号	属性	描述
1	tickTime=2000	心跳，2000毫秒一个心跳；（2秒）
2	initLimit=10	10个2秒， 20秒是Leader和Follower 刚开始（初始化）通信的最大延时时间；如果超过这个时间，则zk服务器认为两者连接失败；
3	syncLimit=5	5个2秒， 10秒是 Leader 和 Follower的在集群正常启动后的通信的最大延时时间；如果超过这个时间，则zk服务器认为两者连接失败；
4	dataDir=/opt/module/zookeeper-3.4.10/zkdata	设置zk数据文件存储路径；
5	clientPort=2181	客户端访问 zk 服务的所在主机的端口号；

【3】搭建集群模式的zk

步骤1：201机器，在zoo.cfg下增加集群配置；

server.A=B.C.D ，如 server.1=192.168.163.201:2888:3888
其中A 等于myid文件的值1；
B表示本服务器地址 192.168.163.201；
C表示本服务器与集群中 Leader服务器交换信息的端口；两者同步的数据是数据副本； 2888；
D表示在选举Leader服务器时，服务器间相互通信的端口； 3888；

小结：添加如下配置：

server.1=192.168.163.201:2888:3888
server.2=192.168.163.202:2888:3888
server.3=192.168.163.203:2888:3888

[root@localhost module]# cat zookeeper-3.4.10/conf/zoo.cfg
# 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=/opt/module/zookeeper-3.4.10/zkdata
# the port at which the clients will connect
clientPort=2181
# 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=192.168.163.201:2888:3888
server.2=192.168.163.202:2888:3888
server.3=192.168.163.203:2888:3888

步骤2：201机器，设置服务器编号，在zkdata文件夹下新建myid，内容为1；

[root@localhost zkdata]# pwd
/opt/module/zookeeper-3.4.10/zkdata
[root@localhost zkdata]# echo "1" > myid

步骤3：把201机器下的 zookeeper 文件夹同步到202,203机器；

[root@localhost module]# rsync -azv zookeeper-3.4.10/ root@192.168.163.202:/opt/module/zookeeper-3.4.10/
[root@localhost module]# rsync -azv zookeeper-3.4.10/ root@192.168.163.203:/opt/module/zookeeper-3.4.10/

步骤4：修改 202机器的myid为2， 203机器的myid为3 ；

-- 202机器
[root@localhost zookeeper-3.4.10]# cat zkdata/myid
2

-- 203 机器
[root@localhost zookeeper-3.4.10]# cat zkdata/myid
3

步骤5：启动zk集群

-- 201机器-启动失败
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
[root@localhost zookeeper-3.4.10]#

-- 202机器-启动成功-并且成为leader
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: leader
[root@localhost zookeeper-3.4.10]#

注： zk的选举机制，自行google，这里不再赘述；

-- 203机器-启动成功-follower
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@localhost zookeeper-3.4.10]#
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower

我们再回头查看201机器的zk状态；当202,203启动zk线程后，我们再次查看201的zk状态为成功且是 follower；

-- 201
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@localhost zookeeper-3.4.10]# bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
[root@localhost zookeeper-3.4.10]# --  ### 我是分割线， 202,203开启zk线程后，[root@localhost zookeeper-3.4.10]# bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower
[root@localhost zookeeper-3.4.10]#

至此，zk集群启动成功；

【4】其他

【4.1】zookeeper 选举机制

1）半数机制：当有半数以上机器存活，则集群可用；否则不可用；（不包括半数）；建议zookeeper 集群的机器数量为奇数；
2）虽然配置文件没有指定 master 和 slave，但在工作时， zookeeper临时选择一条机器作为 master或 leader，其他机器为 slave或follower；

【4.2】zk客户端命令行

-- zk客户端常用命令
ls create get delete rmr set

登录zk客户端

[root@localhost zookeeper-3.4.10]# bin/zkCli.sh

1） ls 查看节点

ls2 查看节点详情

[zk: localhost:2181(CONNECTED) 0] ls /
[zookeeper]
[zk: localhost:2181(CONNECTED) 1] ls2 /
[zookeeper]
cZxid = 0x0
ctime = Thu Jan 01 08:00:00 CST 1970
mZxid = 0x0
mtime = Thu Jan 01 08:00:00 CST 1970
pZxid = 0x0
cversion = -1
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 0
numChildren = 1
[zk: localhost:2181(CONNECTED) 2]

stat结构体

序号	key	描述
1	cZxid	创建事务编号
2	ctime	创建时间
3	mZxid	修改事务编号
4	mtime	修改时间
5	pZxid	最后更新的子节点
6	cversion	子节点变化编号
7	dataVersion	数据变化编号
8	aclVersion	访问控制列表的变化号
9	ephemeralOwner	若是临时节点，表示的是znode拥有者的session id，如果不是，则是0
10	dataLength	znode的数据长度
11	numChildren	znode的子节点个数

2）create 创建节点

[zk: localhost:2181(CONNECTED) 2] create /sichuan "sichuan"
Created /sichuan
[zk: localhost:2181(CONNECTED) 3] ls /
[sichuan, zookeeper]

3）get 获取节点

[zk: localhost:2181(CONNECTED) 4] get /sichuan
sichuan
cZxid = 0x100000002
ctime = Sun Dec 20 04:22:16 CST 2020
mZxid = 0x100000002
mtime = Sun Dec 20 04:22:16 CST 2020
pZxid = 0x100000002
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 7
numChildren = 0
[zk: localhost:2181(CONNECTED) 5]

4）delete 删除节点

[zk: localhost:2181(CONNECTED) 5] create /sichuan/cd "chengdu"
Created /sichuan/cd
[zk: localhost:2181(CONNECTED) 7] create /sichuan/leshan "leshan4"
Created /sichuan/leshan
[zk: localhost:2181(CONNECTED) 8] ls /sichuan
[cd, leshan]
[zk: localhost:2181(CONNECTED) 9] delete /sichuan/leshan
[zk: localhost:2181(CONNECTED) 10]
[zk: localhost:2181(CONNECTED) 10] ls /sichuan
[cd]
[zk: localhost:2181(CONNECTED) 11]

5）rmr 递归删除当前目录及其下的所有子目录

[zk: localhost:2181(CONNECTED) 10] ls /sichuan
[cd]
[zk: localhost:2181(CONNECTED) 11] create /sichuan/my "mianyang"
Created /sichuan/my
[zk: localhost:2181(CONNECTED) 12] ls /sichuan
[cd, my]
[zk: localhost:2181(CONNECTED) 13] rmr /sichuan
[zk: localhost:2181(CONNECTED) 14]
[zk: localhost:2181(CONNECTED) 14] ls /sichuan
Node does not exist: /sichuan

6）set 设置节点存储的值

[zk: localhost:2181(CONNECTED) 18] create /china "china"
Created /china
[zk: localhost:2181(CONNECTED) 19] [zk: localhost:2181(CONNECTED) 19] get /china
china
cZxid = 0x10000000b
ctime = Sun Dec 20 04:28:10 CST 2020
mZxid = 0x10000000b
mtime = Sun Dec 20 04:28:10 CST 2020
pZxid = 0x10000000b
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0[zk: localhost:2181(CONNECTED) 20] set /china "china xiongqi"
cZxid = 0x10000000b
ctime = Sun Dec 20 04:28:10 CST 2020
mZxid = 0x10000000c
mtime = Sun Dec 20 04:28:35 CST 2020
pZxid = 0x10000000b
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 0[zk: localhost:2181(CONNECTED) 21] get /china
china xiongqi
cZxid = 0x10000000b
ctime = Sun Dec 20 04:28:10 CST 2020
mZxid = 0x10000000c
mtime = Sun Dec 20 04:28:35 CST 2020
pZxid = 0x10000000b
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 0
[zk: localhost:2181(CONNECTED) 22]

7）zk有4种节点类型：

1、类型1-持久目录节点： 客户端与服务器断开后，创建的节点不删除；
2、类型2-持久化顺序编号目录节点：客户端与服务器断开连接后，该节点依旧存在，只是zookeeper 给该节点名称进行顺序编号；
应用场景：在分布式系统中，顺序号可以被用于为所有的事件进行全局排序，这样客户端可以通过顺序号推断事件的顺序；（哪台服务器先上，哪台服务器后上）
3、类型3-临时目录节点：两者断开后，创建的节点被删除；
应用场景： zk 服务器监听某台客户端机器的状态；若客户端机器下线，则zk服务器节点也删除；集群从而间接知晓客户端机器下线；（服务器节点动态上下线）
4、类型4-临时顺序编号目录节点：客户端与服务器断开后，该节点被删除；只是 zk 对该服务器节点名称进行了顺序编号；

8）荔枝：创建有序节点（-s）创建临时节点 -e

有序节点

-- 创建有序节点
[zk: localhost:2181(CONNECTED) 24] ls /china
[]
[zk: localhost:2181(CONNECTED) 25] create -s /china/beijing "beijing"
Created /china/beijing0000000000
[zk: localhost:2181(CONNECTED) 26] create -s /china/beijing "beijing"
Created /china/beijing0000000001
[zk: localhost:2181(CONNECTED) 27] create -s /china/beijing "beijing"
Created /china/beijing0000000002
[zk: localhost:2181(CONNECTED) 28] create -s /china/beijing "beijing"
Created /china/beijing0000000003
[zk: localhost:2181(CONNECTED) 29] ls /china
[beijing0000000001, beijing0000000000, beijing0000000003, beijing0000000002]

创建临时+有序节点（chongqing）

[zk: localhost:2181(CONNECTED) 31] create -e -s /china/chongqing "chongqing4"
Created /china/chongqing0000000004
[zk: localhost:2181(CONNECTED) 32]
[zk: localhost:2181(CONNECTED) 32] ls /china
[beijing0000000001, beijing0000000000, chongqing0000000004, beijing0000000003, beijing0000000002]

退出当前客户端 quit 并再次登录客户端，发现chognqing节点被删除了；

[zk: localhost:2181(CONNECTED) 33] quit
Quitting...
2020-12-20 04:38:48,888 [myid:] - INFO  [main:ZooKeeper@684] - Session: 0x1767ca215950000 closed
2020-12-20 04:38:48,890 [myid:] - INFO  [main-EventThread:ClientCnxn$EventThread@519] - EventThread shut down for session: 0x1767ca215950000
[root@localhost zookeeper-3.4.10]#
[root@localhost zookeeper-3.4.10]# bin/zkCli.sh[zk: localhost:2181(CONNECTED) 0] ls /china
[beijing0000000001, beijing0000000000, beijing0000000003, beijing0000000002]
[zk: localhost:2181(CONNECTED) 1]

还有话说：为啥 -s是有序，-e是临时。看下zk的java api 的节点类型常量命名就知道了，如下：

/****  CreateMode value determines how the znode is created on ZooKeeper.*/
public enum CreateMode {/*** The znode will not be automatically deleted upon client's disconnect.*/PERSISTENT (0, false, false),/*** The znode will not be automatically deleted upon client's disconnect,* and its name will be appended with a monotonically increasing number.*/PERSISTENT_SEQUENTIAL (2, false, true),/*** The znode will be deleted upon the client's disconnect.*/EPHEMERAL (1, true, false),/*** The znode will be deleted upon the client's disconnect, and its name* will be appended with a monotonically increasing number.*/EPHEMERAL_SEQUENTIAL (3, true, true);

最后，可以通过 zk提供的javaapi 连接 zk集群， refer 2 https://blog.csdn.net/PacosonSWJTU/article/details/111404364