centos8平台安装zookeeper3.6集群

孤街浪徒 提交于 2020-03-21 17:31:02

一,规划三台zk服务器构成集群

ip:172.18.1.1        机器名:zk1     对应myid: 1
ip:172.18.1.2        机器名:zk2     对应myid: 2
ip:172.18.1.3        机器名:zk3     对应myid: 3

 

说明:为什么zookeeper集群的数量需要是单数?

1,为了容错,增删改操作中需要半数以上服务器通过才算成功,

2,防脑裂,一个zookeeper集群中,必需有且只能有一台leader服务器

    当leader服务器宕机时,剩下的服务器会通过半数以上投票选出一个新的leader服务器

集群总数共2台时,半数是1,半数以上最少是2,也就是一台也不能宕机

集群总数共3台时,半数是1.5,半数以上最少是2,也就是允许一台能宕机
集群总数共4台时,半数是2,半数以上最少是3,也就是允许一台能宕机

集群总数共5台时,半数是2.5,半数以上最少是3,也就是允许两台能宕机,
集群总数共6台时,半数是3,半数以上最少是4,也就是允许两台能宕机,

可见

    允许两台能宕机:5台比6台成本更低

    允许一台能宕机:3台比4台成本更低

 

说明:刘宏缔的架构森林是一个专注架构的博客,地址:https://www.cnblogs.com/architectforest

         对应的源码可以访问这里获取: https://github.com/liuhongdi/

 说明:作者:刘宏缔 邮箱: 371125307@qq.com

 

二,在每台服务器上安装zookeeper之安装java

说明:jdk的安装包请从java官方站下载

1,解压并安装

[root@zookeeper ~]# cd /usr/local/source/
[root@zookeeper source]# tar -zxvf jdk-13.0.2_linux-x64_bin.tar.gz
[root@zookeeper source]# mkdir /usr/local/soft
[root@zookeeper source]# mv jdk-13.0.2 /usr/local/soft/

 

2,配置环境变量:

[root@zookeeper source]# vi /etc/profile

在末尾处添加环境变量:

export JAVA_HOME=/usr/local/soft/jdk-13.0.2
export JRE_HOME=${JAVA_HOME}/jre
export CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin

使环境变量生效:

[root@zookeeper source]# source /etc/profile

 

3,查看版本,检验安装是否生效

[root@zookeeper source]# java --version
java 13.0.2 2020-01-14
Java(TM) SE Runtime Environment (build 13.0.2+8)
Java HotSpot(TM) 64-Bit Server VM (build 13.0.2+8, mixed mode, sharing)

 

三,在每台服务器上安装zookeeper之安装zookeeper

1,安装wget,供文件下载时使用:

[root@zookeeper source]# yum install wget

 

2,下载zookeeper

[root@zookeeper source]# wget https://downloads.apache.org/zookeeper/zookeeper-3.6.0/apache-zookeeper-3.6.0-bin.tar.gz

 

3,解压,安装

[root@zookeeper source]# tar -zxvf apache-zookeeper-3.6.0-bin.tar.gz
[root@zookeeper source]# mv apache-zookeeper-3.6.0-bin/ /usr/local/soft/

 

4,创建数据和日志目录

[root@zookeeper source]# mkdir -p /data/zookeeper
[root@zookeeper source]# mkdir -p /data/zookeeper/data
[root@zookeeper source]# mkdir -p /data/zookeeper/datalogs
[root@zookeeper source]# mkdir -p /data/zookeeper/logs

说明:

      data:数据目录

      datalogs:事务日志

      logs:zk应用的日志

5,生成配置文件:

[root@zookeeper source]# cd /usr/local/soft/apache-zookeeper-3.6.0-bin/conf/
[root@zookeeper conf]# cp zoo_sample.cfg zoo.cfg 

 

6,设置配置文件:

[root@zookeeper conf]# vi zoo.cfg

内容:

dataDir=/data/zookeeper/data
dataLogDir=/data/zookeeper/datalogs
admin.enableServer=false

说明:admin.enableServer=false 用来关闭zk内置的web管理器

dataDir 定义了zk的数据目录

dataLogDir 定义了zk的事务日志

 

7,配置环境变量

[root@zookeeper conf]# vi /etc/profile

在末尾增加以下内容:

export ZK_HOME=/usr/local/soft/apache-zookeeper-3.6.0-bin
export PATH=$ZK_HOME/bin:$PATH

使环境变量生效:

[root@zookeeper conf]# source /etc/profile

 

8,测试启动和停止zookeeper

[root@zookeeper conf]# zkServer.sh start
[root@zookeeper conf]# zkServer.sh stop

 

四,在每台服务器上安装zookeeper之使zookeeper支持systemd

1,修改zkEnv.sh这个脚本

[root@zookeeper conf]# vi /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/zkEnv.sh

添加如下一行

JAVA_HOME=/usr/local/soft/jdk-13.0.2

到ZOOBINDIR=一行的上方

说明:为了解决从systemctl启动时找不到java而报错

 

2,找到ZOO_LOG_DIR一行,修改为:

ZOO_LOG_DIR="/data/zookeeper/logs"

用来记录zk运行时的日志

 

3,增加service文件,用来供systemd启动使用:

[root@zookeeper conf]# vi /etc/systemd/system/zookeeper.service

内容:

[Unit]
Description=zookeeper.service
After=network.target
ConditionPathExists=/usr/local/soft/apache-zookeeper-3.6.0-bin/conf/zoo.cfg

[Service]
Type=forking
User=root
Group=root
ExecStart=/usr/local/soft/apache-zookeeper-3.6.0-bin/bin/zkServer.sh start
ExecStop=/usr/local/soft/apache-zookeeper-3.6.0-bin/bin/zkServer.sh stop

[Install]
WantedBy=multi-user.target

 

3,测试启动/停止zk:

[root@zookeeper conf]# systemctl daemon-reload
[root@zookeeper conf]# systemctl start zookeeper
[root@zookeeper conf]# systemctl stop zookeeper

 

五,在每台服务器上安装zookeeper之查看当前已安装zk的版本:

1,安装nc,查看版本时作为工具使用

[root@zookeeper conf]# yum install nc

 

2,显示版本时会报错

[root@zookeeper conf]# echo stat|nc 127.0.0.1 2181
stat is not executed because it is not in the whitelist.

解决:

[root@zookeeper conf]# vi /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/zkServer.sh

在这个fi下面添加一行

ZOOMAIN="org.apache.zookeeper.server.quorum.QuorumPeerMain"
fi

新加一行:

ZOOMAIN="-Dzookeeper.4lw.commands.whitelist=* ${ZOOMAIN}"

保存退出后重启服务:

[root@zookeeper conf]# systemctl stop zookeeper
[root@zookeeper conf]# systemctl start zookeeper

 

3,再次查看zk版本

[root@zookeeper conf]# echo stat|nc 127.0.0.1 2181
Zookeeper version: 3.6.0--b4c89dc7f6083829e18fae6e446907ae0b1f22d7, built on 02/25/2020 14:38 GMT
Clients:
 /127.0.0.1:47654[0](queued=0,recved=1,sent=0)
Latency min/avg/max: 0/0.0/0
Received: 1
Sent: 0
Connections: 1
Outstanding: 0
Zxid: 0x0
Mode: standalone
Node count: 5

 

六,在三台zookeeper服务器上做集群配置

1,配置文件中增加集群配置

[root@zk1 ~]# vi /usr/local/soft/apache-zookeeper-3.6.0-bin/conf/zoo.cfg

添加如下配置内容

#cluster
server.1=172.18.1.1:2888:3888
server.2=172.18.1.2:2888:3888
server.3=172.18.1.3:2888:3888

 

说明:server.n  n是一个数字,表示zookeeper服务器的序号

      2888是在集群中follower连接到leader时使用的端口,

     也就是:leader上开放此端口,follower连接到leader此端口访问数据

     3888:集群内进行leader选举时使用的端口

说明:三台机器上都添加此集群配置,   配置内容相同

 

2,给每个机器指定id

在每台机器上zoo.cfg里dataDir指定的目录下,生成一个id值文件:myid

说明:myid内的值,要和本机ip对应的zoo.cfg中序号一致

zk1(172.18.1.1)上

[root@zk1 ~]# vi /data/zookeeper/data/myid
[root@zk1 ~]# more /data/zookeeper/data/myid 
1

 

zk2(172.18.1.2)上

[root@zk2 ~]# vi /data/zookeeper/data/myid
[root@zk2 ~]# more /data/zookeeper/data/myid
2

 

zk3(172.18.1.3)上

[root@zk3 ~]# vi /data/zookeeper/data/myid
[root@zk3 ~]# more /data/zookeeper/data/myid
3

 

七,逐台启动服务器,检查各zookeeper的状态

1,启动zk服务

在三台机器上分别执行:

systemctl start zookeeper

 

2,分别在三台机器上检查状态:

[root@zk1 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: follower

它的工作模式是: follower

 

[root@zk2 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: leader

它的工作模式是: leader

 

[root@zk3 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: follower

它的工作模式是: follower

 

3,mode也可以用stat这个四字命令查看,例子:

[root@zk1 ~]# echo stat | nc 172.18.1.1 2181
Zookeeper version: 3.6.0--b4c89dc7f6083829e18fae6e446907ae0b1f22d7, built on 02/25/2020 14:38 GMT
Clients:
 /172.18.1.1:59284[0](queued=0,recved=1,sent=0)
Latency min/avg/max: 0/1.9375/41
Received: 34
Sent: 33
Connections: 1
Outstanding: 0
Zxid: 0x100000004
Mode: follower
Node count: 6

 

4,单机方式运行的zookeeper服务的mode是什么?

[root@zk /]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: standalone

可以看到,其Mode是standalone

 

八,测试:连接到zk服务,创建一个znode

1,在zk3上创建节点:

[root@zk3 ~]# zkCli.sh -server localhost
[zk: localhost(CONNECTED) 0] ls /
[zookeeper]
[zk: localhost(CONNECTED) 1] create /demo 'this is a demo'
Created /demo
[zk: localhost(CONNECTED) 2] ls /
[demo, zookeeper]

 

2,从zk1上查看节点:

[root@zk1 ~]# zkCli.sh -server localhost
[zk: localhost(CONNECTED) 2] get /demo
this is a demo

可见创建的节点已同步到了zk1

 

九,测试:模拟zk集群一个节点发生故障后的处理?

1,当前zk2是leader,我们停掉它,然后看各服务器的mode变化:

停掉zk2

[root@zk2 ~]# systemctl stop zookeeper

 

zk1上查看状态

[root@zk1 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: follower

zk1仍然是follower

 

zk3上查看状态

[root@zk3 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: leader

zk3变成了leader

 

2,重新启动zk2:

[root@zk2 ~]# systemctl start zookeeper

 

再次查看状态,变成了 follower

[root@zk2 ~]# zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /usr/local/soft/apache-zookeeper-3.6.0-bin/bin/../conf/zoo.cfg
Client port found: 2181. Client address: localhost.
Mode: follower

 

3,在zk1上写入数据,从zk2上观察效果

[root@zk1 ~]# zkCli.sh -server localhost
[zk: localhost(CONNECTED) 1] create /demo2 'demo2'
Created /demo2
[zk: localhost(CONNECTED) 2] get /demo2
demo2

 

回到zk2

[root@zk2 ~]# zkCli.sh -server localhost
[zk: localhost(CONNECTED) 1] get /demo2
demo2

 

4,结论:zookeeper的集群模式能有效的防止单点故障

 

十,查看centos的版本

[root@localhost liuhongdi]# cat /etc/redhat-release
CentOS Linux release 8.1.1911 (Core)

 

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