ZooKeeper 是一种分布式协调服务。在分布式环境中协调和管理服务是一个复杂的过程。 ZooKeeper 使用简单的架构和API解决了这个问题。 ZooKeeper 允许开发人员专注于核心应用程序逻辑，而不必担心应用程序的分布式性质。zkui 是一个提供了 ZooKeeper CRUD 操作的 UI。 本文介绍 ZooKeeper 的简单搭建过程及zkui的配置。

使用 Vagrant 创建三台 Zookeeper 虚拟机，三台虚拟机分布在三台物理机，基本信息如下：

Name ADDRESS HOSTNAME
zookeeper1 172.16.63.101 zookeeper1
zookeeper2 172.16.63.102 zookeeper2
zookeeper3 172.16.63.103 zookeeper3

ZooKeeper 的搭建在任意一台机器上的过程都是一样的，这里以 zookeeper1 为例进行说明：

# 设置 MaxHeapSize 以 Avoid swapping
[vagrant@zookeeper1 ~]$ export _JAVA_OPTIONS="-Xmx3072m"
# 下载安装包
[vagrant@zookeeper1 ~]$ wget http://apache.mirrors.ionfish.org/zookeeper/stable/zookeeper-3.4.9.tar.gz
[vagrant@zookeeper1 ~]$ tar xvf zookeeper-3.4.9.tar.gz
[vagrant@zookeeper1 ~]$ cd zookeeper-3.4.9/
# 配置文件重命名为zoo.cfg
[vagrant@zookeeper1 zookeeper-3.4.9]$ mv conf/zoo_sample.cfg conf/zoo.cfg
# 编辑 conf/zoo.cfg
[vagrant@zookeeper1 zookeeper-3.4.9]$ cat 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=/data/zookeeper
# 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

# ZooKeeper集群含三台机器，本机的Server应该配置为IP: 0.0.0.0，这点很重要
server.1=0.0.0.0:2888:3888
server.2=zookeeper2:2888:3888
server.3=zookeeper3:2888:3888
[vagrant@zookeeper1 zookeeper-3.4.9]$

在/data/zookeeper下创建一个名为myid的文件，并填写自己的Server ID，zookeeper1 对应 1，zookeeper2 对应 2， zookeeper3 对应 3。

启动ZooKeeper

[vagrant@zookeeper1 zookeeper-3.4.9]$ bin/zkServer.sh start
# 查看日志
[vagrant@zookeeper1 zookeeper-3.4.9]$ tail -f zookeeper.out

测试

[vagrant@zookeeper1 zookeeper-3.4.9]$ bin/zkCli.sh
Picked up _JAVA_OPTIONS: -Xmx3072m
Connecting to localhost:2181
2017-03-22 07:45:28,716 [myid:] - INFO  [main:Environment@100] - Client environment:zookeeper.version=3.4.9-1757313, built on 08/23/2016 06:50 GMT
2017-03-22 07:45:28,720 [myid:] - INFO  [main:Environment@100] - Client environment:host.name=zookeeper1
2017-03-22 07:45:28,720 [myid:] - INFO  [main:Environment@100] - Client environment:java.version=1.8.0_121
2017-03-22 07:45:28,723 [myid:] - INFO  [main:Environment@100] - Client environment:java.vendor=Oracle Corporation
2017-03-22 07:45:28,723 [myid:] - INFO  [main:Environment@100] - Client environment:java.home=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.121-0.b13.el7_3.x86_64/jre
2017-03-22 07:45:28,723 [myid:] - INFO  [main:Environment@100] - Client environment:java.class.path=/home/vagrant/zookeeper-3.4.9/bin/../build/classes:/home/vagrant/zookeeper-3.4.9/bin/../build/lib/*.jar:/home/vagrant/zookeeper-3.4.9/bin/../lib/slf4j-log4j12-1.6.1.jar:/home/vagrant/zookeeper-3.4.9/bin/../lib/slf4j-api-1.6.1.jar:/home/vagrant/zookeeper-3.4.9/bin/../lib/netty-3.10.5.Final.jar:/home/vagrant/zookeeper-3.4.9/bin/../lib/log4j-1.2.16.jar:/home/vagrant/zookeeper-3.4.9/bin/../lib/jline-0.9.94.jar:/home/vagrant/zookeeper-3.4.9/bin/../zookeeper-3.4.9.jar:/home/vagrant/zookeeper-3.4.9/bin/../src/java/lib/*.jar:/home/vagrant/zookeeper-3.4.9/bin/../conf:
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:java.library.path=/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:java.io.tmpdir=/tmp
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:java.compiler=<NA>
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:os.name=Linux
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:os.arch=amd64
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:os.version=3.10.0-514.6.2.el7.x86_64
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:user.name=vagrant
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:user.home=/home/vagrant
2017-03-22 07:45:28,724 [myid:] - INFO  [main:Environment@100] - Client environment:user.dir=/home/vagrant/zookeeper-3.4.9
2017-03-22 07:45:28,726 [myid:] - INFO  [main:ZooKeeper@438] - Initiating client connection, connectString=localhost:2181 sessionTimeout=30000 watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@69d0a921
2017-03-22 07:45:28,769 [myid:] - INFO  [main-SendThread(zookeeper1:2181):ClientCnxn$SendThread@1032] - Opening socket connection to server zookeeper1/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)
Welcome to ZooKeeper!
JLine support is enabled
2017-03-22 07:45:28,944 [myid:] - INFO  [main-SendThread(zookeeper1:2181):ClientCnxn$SendThread@876] - Socket connection established to zookeeper1/127.0.0.1:2181, initiating session
2017-03-22 07:45:28,966 [myid:] - INFO  [main-SendThread(zookeeper1:2181):ClientCnxn$SendThread@1299] - Session establishment complete on server zookeeper1/127.0.0.1:2181, sessionid = 0x15af4d71e230001, negotiated timeout = 30000

WATCHER::

WatchedEvent state:SyncConnected type:None path:null
[zk: localhost:2181(CONNECTED) 0] ls /
[zookeeper]
[zk: localhost:2181(CONNECTED) 1] create /hello my_data
Created /hello
[zk: localhost:2181(CONNECTED) 2] ls /
[hello, zookeeper]
[zk: localhost:2181(CONNECTED) 3] get /hello
my_data
cZxid = 0x100000006
ctime = Wed Mar 22 07:47:01 UTC 2017
mZxid = 0x100000006
mtime = Wed Mar 22 07:47:01 UTC 2017
pZxid = 0x100000006
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 7
numChildren = 0
[zk: localhost:2181(CONNECTED) 4] set /hello another_data
cZxid = 0x100000006
ctime = Wed Mar 22 07:47:01 UTC 2017
mZxid = 0x100000007
mtime = Wed Mar 22 07:47:25 UTC 2017
pZxid = 0x100000006
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 0
[zk: localhost:2181(CONNECTED) 5] get /hello
another_data
cZxid = 0x100000006
ctime = Wed Mar 22 07:47:01 UTC 2017
mZxid = 0x100000007
mtime = Wed Mar 22 07:47:25 UTC 2017
pZxid = 0x100000006
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 0
[zk: localhost:2181(CONNECTED) 6]

ZKUI

ZKUI 到现在我都没有构建成功，只好使用docker镜像来启动应用，比较简单，不多说了，大家知道有这么个工具就行了。


Reference:
1 ZooKeeper Administrator’s Guide
2 Zookeeper error: Cannot open channel to X at election address