本文讲述单机环境下，如何搭建一个zookeeper集群。
方式一是在本地机器上，利用三个端口模拟三个zk服务器，准备三份zk配置文件，搭建zk集群。
方式二在本地机器上，通过docker compose搭建zk集群。
方式一：纯手工搭建一个zookeeper集群
集群包含3个节点，使用端口号2181，2182，2183.
- 准备好3个节点的配置文件。
zoo.cfg默认在/usr/local/etc/zookeeper目录下。在这个目录下创建zoo1.cfg zoo2.cfg zoo3.cfg.
其中，各个节点需要配置相应的dataDir，clientPort。
另外，server.1, server.2, server.3是集群配置信息，表明构成集群的3个节点。
例如server.A=B:D:D. 这里的A是一个数字，表示服务器的编号。B是这个服务器的ip地址。C是zookeeper服务器之间通信端口。D是Leader选举的端口。
zookeeper $ cat zoo1.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=/usr/local/var/run/zookeeper/zk1/data
# 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=localhost:2287:3387
server.2=localhost:2288:3388
server.3=localhost:2289:3389
zookeeper $ cat zoo2.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=/usr/local/var/run/zookeeper/zk2/data
# the port at which the clients will connect
clientPort=2182
# 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=localhost:2287:3387
server.2=localhost:2288:3388
server.3=localhost:2289:3389
zookeeper $ cat zoo3.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=/usr/local/var/run/zookeeper/zk3/data
# the port at which the clients will connect
clientPort=2183
# 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=localhost:2287:3387
server.2=localhost:2288:3388
server.3=localhost:2289:3389
- 创建data目录和myid文件
#创建如下data目录
/usr/local/var/run/zookeeper/zk1/data
/usr/local/var/run/zookeeper/zk2/data
/usr/local/var/run/zookeeper/zk3/data
#创建如下myid文件
data $ cat /usr/local/var/run/zookeeper/zk1/data/myid
1
data $ cat /usr/local/var/run/zookeeper/zk2/data/myid
2
data $ cat /usr/local/var/run/zookeeper/zk3/data/myid
3
- 启动3个zookeeper
$ zkServer start /usr/local/etc/zookeeper/zoo1.cfg
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo1.cfg
Starting zookeeper ... STARTED
$ zkServer start /usr/local/etc/zookeeper/zoo2.cfg
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo2.cfg
Starting zookeeper ... STARTED
$ zkServer start /usr/local/etc/zookeeper/zoo3.cfg
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo3.cfg
Starting zookeeper ... STARTED
- 查看各个节点的状态：1个leader，2个follower
$ zkServer status /usr/local/etc/zookeeper/zoo1.cfg
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo1.cfg
Mode: follower
zkServer status /usr/local/etc/zookeeper/zoo2.cfg
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo2.cfg
Mode: follower
$ zkServer status /usr/local/etc/zookeeper/zoo3.cfg
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo3.cfg
Mode: leader
- 进入zookeeper集群内部，登陆各个节点
$ zkCli -server localhost:2181
Connecting to localhost:2181
Welcome to ZooKeeper!
JLine support is enabled
WATCHER::
WatchedEvent state:SyncConnected type:None path:null
$ zkCli -server localhost:2182
$ zkCli -server localhost:2183
#在zk1上新建一个node，到zk2和3上能够马上查看到
[zk: localhost:2181(CONNECTED) 1] create /test-zk1 "test-zk1"
Created /test-zk1
[zk: localhost:2182(CONNECTED) 1] get /test-zk1
test-zk1
cZxid = 0x100000007
ctime = Sat Mar 13 22:05:00 CST 2021
mZxid = 0x100000007
mtime = Sat Mar 13 22:05:00 CST 2021
pZxid = 0x100000007
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 8
numChildren = 0
[zk: localhost:2183(CONNECTED) 0] get /test-zk1
test-zk1
cZxid = 0x100000007
ctime = Sat Mar 13 22:05:00 CST 2021
mZxid = 0x100000007
mtime = Sat Mar 13 22:05:00 CST 2021
pZxid = 0x100000007
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 8
numChildren = 0
方式二：用docker compose搭建一个zookeeper集群
方式一中需要准备3份配置文件，启动3次zk服务，比较麻烦。那么用docker compose可以更快捷地通过容器搭建zk集群。
- 通过docker下载zookeeper镜像。如果对docker compose不了解，可以参考docker系列中的 Docker安装及原理
和 Docker compose介绍及常用命令
$ docker pull zookeeper:3.4.13
$ docker images |grep zookeeper
zookeeper 3.4.13 4ebfb9474e72 23 months ago 150 MB
- 准备docker-compose.yaml
注意yaml文件有很严格的语法标准，符号：和-后都需要有空格，否则会报错。
$ cat docker-compose.yaml
version: '3.1'
services:
zoo1:
image: zookeeper:3.4.13
restart: always
hostname: zoo1
container_name: zoo1
ports:
- "2181:2181"
environment:
ZOO_MY_ID: 1
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
zoo2:
image: zookeeper:3.4.13
restart: always
hostname: zoo2
container_name: zoo2
ports:
- "2182:2181"
environment:
ZOO_MY_ID: 2
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
zoo3:
image: zookeeper:3.4.13
restart: always
hostname: zoo3
container_name: zoo3
ports:
- "2183:2181"
environment:
ZOO_MY_ID: 3
ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
- 启动并测试
#启动docker容器
$ docker-compose up
Creating network "zookeeper_default" with the default driver
Creating zoo1
Creating zoo2
Creating zoo3
#查看，3个容器被创建好了
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b7bd4fb6e17b zookeeper:3.4.13 "/docker-entrypoin..." 32 hours ago Up 2 minutes 2888/tcp, 3888/tcp, 0.0.0.0:2182->2181/tcp zoo2
2b0dde93bea9 zookeeper:3.4.13 "/docker-entrypoin..." 32 hours ago Up 2 minutes 2888/tcp, 3888/tcp, 0.0.0.0:2183->2181/tcp zoo3
9c3d91824726 zookeeper:3.4.13 "/docker-entrypoin..." 32 hours ago Up 2 minutes 2888/tcp, 0.0.0.0:2181->2181/tcp, 3888/tcp zoo1
#查看集群状态，一个leader，两个follower
$ docker exec -it zoo1 bash ./bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /conf/zoo.cfg
Mode: follower
$ docker exec -it zoo2 bash ./bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /conf/zoo.cfg
Mode: leader
$ docker exec -it zoo3 bash ./bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /conf/zoo.cfg
Mode: follower
- 进入容器中的集群节点，查看集群上的数据
#登陆zoo2，查看数据
##############
zookeeper $ docker exec -it zoo2 /bin/bash
bash-4.4# pwd
/zookeeper-3.4.13
bash-4.4# ./bin/zkCli.sh -server localhost:2181
Connecting to localhost:2181
2021-03-12 19:22:04,234 [myid:] - INFO [main:Environment@100] - Client environment:zookeeper.version=3.4.13-2d71af4dbe22557fda74f9a9b4309b15a7487f03, built on 06/29/2018 04:05 GMT
......
[zk: localhost:2181(CONNECTED) 0] ls /
[zookeeper]
#登陆zoo1，查看数据
################
$ docker exec -it zoo1 /bin/bash
bash-4.4# ./bin/zkCli.sh -server localhost:2181
[zk: localhost:2181(CONNECTED) 1] ls /
[zookeeper]
#在zoo2上新建一个节点，到zoo1上可以看到
#################
#zoo2
[zk: localhost:2181(CONNECTED) 2] create /zoo2 "zoo2-create"
Created /zoo2
#zoo1
[zk: localhost:2181(CONNECTED) 1] ls /
[zoo2, zookeeper]
