1 概述
1.1 zookeeper 简介
- 中间件，提供协调服务
- 作用于分布式系统，发挥其优势，为大数据服务
- 支持 Java，提供 Java 和 C语言的客户端 API
1.2 什么是分布式系统
- 很多台计算机组成一个整体,一个整体一致对外并且处理同一请求
- 内部的每台计算机都可以相互通信(REST/RPC)
- 客户端到服务端的一次请求到响应结束会经历多台计算机
1.3 分布式系统的瓶颈
1.3.1 zookeeper 的特性
- 一致性数据一致性,数据按照顺序分批入库
- 原子性事务要么成功要么失败,不会局部化
- 单一视图客户端连接集群中的任一 zk 节点,数据都是一致的
- 可靠性每次对 zk的操作状态都会保存在服务端
- 实时性客户端可以读取到 zk 服务端的最新数据
2 下载、安装以及配置
安装 JDK
2.1 单机模式
2.1.1 Linux环境操作
linux etc/profile：
2.1.2 Mac OS操作
$brew install zookeeper
==> Downloading https://homebrew.bintray.com/bottles/zookeeper-3.4.6_1.mavericks.bottle.2.tar.gz
######################################################################## 100.0%
==> Pouring zookeeper-3.4.6_1.mavericks.bottle.2.tar.gz
==> Caveats
To have launchd start zookeeper at login:
ln -sfv /usr/local/opt/zookeeper/*.plist ~/Library/LaunchAgents
Then to load zookeeper now:
launchctl load ~/Library/LaunchAgents/homebrew.mxcl.zookeeper.plist
Or, if you don't want/need launchctl, you can just run:
zkServer start
==> Summary
安装成功后，在/usr/local/etc/zookeeper/目录，已有默认配置文件
$ cd /usr/local/etc/zookeeper/
$ ls
zoo.cfg
配置[/usr/local/etc/zookeeper/zoo.cfg] 文件
# 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/data
dataLogDir=/usr/local/var/run/zookeeper/log
# the port at which the clients will connect
clientPort=2181
bin下的可执行文件：
手动下载
下载tar包解压，推荐使用3.5.x，不要使用3.6以高版本，和JDK1.8冲突，事到如今，也不要直接brew install zookeeper--默认会下载最高版本！很难用！
下载二进制安装包：
https://www.apache.org/dyn/closer.lua/zookeeper/zookeeper-3.5.10/apache-zookeeper-3.5.10-bin.tar.gz
解压缩：
tar -zxvf apache-zookeeper-3.5.10-bin.tar.gz
将conf目录下的zoo_sample.cfg文件更名为zoo.cfg，简单修改配置文件，自定义设置数据文件目录和日志文件目录。
新建文件夹data和log：
$ zookeeper-3.5.10 ll
total 48
-rw-r--r--@ 1 sss admin 11K 5 19 2022 LICENSE.txt
-rw-r--r--@ 1 sss admin 432B 5 19 2022 NOTICE.txt
-rw-r--r--@ 1 sss admin 1.5K 5 19 2022 README.md
-rw-r--r--@ 1 sss admin 1.3K 5 19 2022 README_packaging.txt
drwxr-xr-x@ 13 sss admin 416B 5 19 2022 bin
drwxr-xr-x@ 5 sss admin 160B 3 8 17:49 conf
drwxr-xr-x 2 sss admin 64B 3 8 17:50 data
drwxr-xr-x@ 21 sss admin 672B 5 29 2022 docs
drwxr-xr-x 54 sss admin 1.7K 3 8 17:46 lib
drwxr-xr-x 2 sss admin 64B 3 8 17:50 log
修改路径地址：dataDir 和 dataLogDir
# 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=/Volumes/doc/zookeeper-3.5.10/data
dataLogDir=/Volumes/doc/zookeeper-3.5.10/log
# 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
配置环境变量
sudo vi ~/.bash_profile
export ZK_HOME=/Volumes/doc/zookeeper-3.5.10/
export PATH=$PATH:$ZK_HOME/bin
$ cd bin
$ bin zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /Volumes/doc/zookeeper-3.5.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
3 常用命令
3.1 启动
执行命令zkServer：
$ zkServer
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo.cfg
Usage: ./zkServer.sh {start|start-foreground|stop|restart|status|upgrade|print-cmd}
zkServer status
$ zkServer status
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo.cfg
Mode: standalone
zkServer start
$ zkServer start
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo.cfg
Starting zookeeper ... STARTED
brew services start zookeeper
brew services restart zookeeper
3.2 查看运行状态
$ zkServer status
ZooKeeper JMX enabled by default
Using config: /usr/local/etc/zookeeper/zoo.cfg
Mode: standalone
