zookeeper实际上是yahoo开发的,用于分布式中一致性处理的框架。最初其作为研发Hadoop时的副产品。由于分布式系统中一致性处理较为困难,其他的分布式系统没有必要 费劲重复造轮子,故随后的分布式系统中大量应用了zookeeper,以至于zookeeper成为了各种分布式系统的基础组件,其地位之重要,可想而知。著名的hadoop,kafka,dubbo 都是基于zookeeper而构建。
要想理解zookeeper到底是做啥的,那首先得理解清楚,什么是一致性?
所谓的一致性,实际上就是围绕着“看见”来的。谁能看见?能否看见?什么时候看见?举个例子:淘宝后台卖家,在后台上架一件大促的商品,通过服务器A提交到主数据库,假设刚提交后立马就有用户去通过应用服务器B去从数据库查询该商品,就会出现一个现象,卖家已经更新成功了,然而买家却看不到;而经过一段时间后,主数据库的数据同步到了从数据库,买家就能查到了。
假设卖家更新成功之后买家立马就能看到卖家的更新,则称为强一致性
如果卖家更新成功后买家不能看到卖家更新的内容,则称为弱一致性
而卖家更新成功后,买家经过一段时间最终能看到卖家的更新,则称为最终一致性
VMware版本号:12.0.0
CentOS版本:CentOS 7.3.1611
ZooKeeper版本:ZooKeeper-3.4.9.tar.gz
JDK环境:jdk-8u144-linux-x64.tar.gz
JDK 1.8 安装
cd /opt/
wget https://mirrors.tuna.tsinghua.edu.cn/apache/zookeeper/zookeeper-3.4.9/zookeeper-3.4.9.tar.gz
或者在浏览器下载上传至opt 目录
cd /opt/
tar -zxf zookeeper-3.4.9.tar.gz
cd zookeeper-3.4.9
创建data
文件夹 用于存储数据文件
mkdir data logs
创建logs
文件夹 用于存储日志
mkdir logs
使用命令 vi conf/zoo.cfg
创建配置文件并打开,ps (其实目录conf
下有默认的配置文件,但是注释太多,英文一大堆,太乱)
vi /opt/zookeeper-3.4.9/conf/zoo.cfg
编辑内容如下
tickTime = 2000
dataDir = /opt/zookeeper-3.4.9/data
dataLogDir = /opt/zookeeper-3.4.9/logs
tickTime = 2000
clientPort = 2181
initLimit = 5
syncLimit = 2
配置文件描述
tickTime
dataDir
dataLogDir
initLimit
syncLimit
/opt/zookeeper-3.4.9/bin/zkServer.sh start
响应
ZooKeeper JMX enabled by default
Using config: /opt/zookeeper-3.4.9/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
连接到ZooKeeper服务
/opt/zookeeper-3.4.9/bin/zkCli.sh
响应
Connecting to localhost:2181
2017-08-22 16:43:05,954 [myid:] - INFO [main:Environment@100] - Client environment:zookeeper.version=3.4.9-1757313, built on 08/23/2016 06:50 GMT
2017-08-22 16:43:05,958 [myid:] - INFO [main:Environment@100] - Client environment:host.name=node1
2017-08-22 16:43:05,958 [myid:] - INFO [main:Environment@100] - Client environment:java.version=1.8.0_144
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:java.vendor=Oracle Corporation
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:java.home=/usr/lib/jvm/jre
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:java.class.path=/opt/zookeeper-3.4.9/bin/../build/classes:/opt/zookeeper-3.4.9/bin/../build/lib/*.jar:/opt/zookeeper-3.4.9/bin/../lib/slf4j-log4j12-1.6.1.jar:/opt/zookeeper-3.4.9/bin/../lib/slf4j-api-1.6.1.jar:/opt/zookeeper-3.4.9/bin/../lib/netty-3.10.5.Final.jar:/opt/zookeeper-3.4.9/bin/../lib/log4j-1.2.16.jar:/opt/zookeeper-3.4.9/bin/../lib/jline-0.9.94.jar:/opt/zookeeper-3.4.9/bin/../zookeeper-3.4.9.jar:/opt/zookeeper-3.4.9/bin/../src/java/lib/*.jar:/opt/zookeeper-3.4.9/bin/../conf:.:/lib/jvm/lib:/lib/jvm/jre/lib
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:java.library.path=/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:java.io.tmpdir=/tmp
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:java.compiler=<NA>
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:os.name=Linux
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:os.arch=amd64
2017-08-22 16:43:05,967 [myid:] - INFO [main:Environment@100] - Client environment:os.version=3.10.0-514.26.2.el7.x86_64
2017-08-22 16:43:05,968 [myid:] - INFO [main:Environment@100] - Client environment:user.name=root
2017-08-22 16:43:05,968 [myid:] - INFO [main:Environment@100] - Client environment:user.home=/root
2017-08-22 16:43:05,968 [myid:] - INFO [main:Environment@100] - Client environment:user.dir=/opt/zookeeper-3.4.9
2017-08-22 16:43:05,969 [myid:] - INFO [main:ZooKeeper@438] - Initiating client connection, connectString=localhost:2181 sessionTimeout=30000 watcher=org.apache.zookeeper.ZooKeeperMain$MyWatcher@506c589e
Welcome to ZooKeeper!
2017-08-22 16:43:06,011 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@1032] - Opening socket connection to server localhost/0:0:0:0:0:0:0:1:2181. Will not attempt to authenticate using SASL (unknown error)
JLine support is enabled
2017-08-22 16:43:06,164 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@876] - Socket connection established to localhost/0:0:0:0:0:0:0:1:2181, initiating session
2017-08-22 16:43:06,237 [myid:] - INFO [main-SendThread(localhost:2181):ClientCnxn$SendThread@1299] - Session establishment complete on server localhost/0:0:0:0:0:0:0:1:2181, sessionid = 0x15e091bf2020000, negotiated timeout = 30000
WATCHER::
WatchedEvent state:SyncConnected type:None path:null
[zk: localhost:2181(CONNECTED) 0]
/opt/zookeeper-3.4.9/bin/zkServer.sh status
响应
ZooKeeper JMX enabled by default
Using config: /opt/zookeeper-3.4.9/bin/../conf/zoo.cfg
Mode: standalone
/opt/zookeeper-3.4.9/bin/zkServer.sh stop
响应
bin/zkServer.sh stop
ZooKeeper JMX enabled by default
Using config: /opt/zookeeper-3.4.9/bin/../conf/zoo.cfg
Stopping zookeeper ... STOPPED
CentOs7.3 搭建 ZooKeeper-3.4.9 Cluster 集群服务
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