1、Zookeeper熟悉和用途综述

集群 配置:

192.168.32.80  192.168.32.81  192.168.32.82

server 1:
zjtest7-redis:/opt/zookeeper/conf# cat zoo.cfg  | grep -v "^#"
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/opt/zookeeper/server1/data
dataLogDir=/opt/zookeeper/server1/logs
clientPort=2181
server.1=192.168.32.80:2888:3888
server.2=192.168.32.81:2888:3888
server.3=192.168.32.82:2888:3888

server 2:

zjtest7-redis2:/opt/zookeeper/conf# cat zoo.cfg  | grep -v "^#"
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/opt/zookeeper/server2/data
dataLogDir=/opt/zookeeper/server2/logs
clientPort=2181
server.1=192.168.32.80:2888:3888
server.2=192.168.32.81:2888:3888
server.3=192.168.32.82:2888:3888

server 3:

zjtest7-haproxy:/opt/zookeeper/conf# cat zoo.cfg  | grep -v "^#"
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/opt/zookeeper/server3/data
dataLogDir=/opt/zookeeper/server3/logs
clientPort=2181
server.1=192.168.32.80:2888:3888
server.2=192.168.32.81:2888:3888
server.3=192.168.32.82:2888:3888

一个zookeeper 集群 只有一个leader： 类似master/slave模式

/**192.168.32.80 follower
zjtest7-redis:/opt/zookeeper/conf# telnet 192.168.32.80 2181
Trying 192.168.32.80...
Connected to 192.168.32.80.
Escape character is '^]'.
stat
Zookeeper version: 3.4.8--1, built on 02/06/2016 03:18 GMT
Clients:
 /192.168.32.80:54168[0](queued=0,recved=1,sent=0)
 /127.0.0.1:59950[1](queued=0,recved=23550,sent=23550)

Latency min/avg/max: 0/0/111
Received: 25815
Sent: 25814
Connections: 2
Outstanding: 0
Zxid: 0x10000000b
Mode: follower
Node count: 4
Connection closed by foreign host.

/***192.168.32.81 leader

zjtest7-redis:/opt/zookeeper/conf# telnet 192.168.32.81 2181
Trying 192.168.32.81...
Connected to 192.168.32.81.
Escape character is '^]'.
stat
Zookeeper version: 3.4.8--1, built on 02/06/2016 03:18 GMT
Clients:
 /192.168.32.80:40376[0](queued=0,recved=1,sent=0)

Latency min/avg/max: 0/0/0
Received: 2
Sent: 1
Connections: 1
Outstanding: 0
Zxid: 0x10000000b
Mode: leader
Node count: 4
Connection closed by foreign host.

/*******192.168.32.82
zjtest7-redis:/opt/zookeeper/conf# telnet 192.168.32.82 2181
Trying 192.168.32.82...
Connected to 192.168.32.82.
Escape character is '^]'.
stat
Zookeeper version: 3.4.8--1, built on 02/06/2016 03:18 GMT
Clients:
 /192.168.32.80:56173[0](queued=0,recved=1,sent=0)

Latency min/avg/max: 0/0/0
Received: 2
Sent: 1
Connections: 1
Outstanding: 0
Zxid: 0x10000000b
Mode: follower
Node count: 4
Connection closed by foreign host.
zjtest7-redis:/opt/zookeeper/conf# 

客户端提交请求之后,先发送到leader,leader作为接收者,广播到每个server

znode ：
节点/NameService/Server1 唯一路径（Node），且携带数据

即是目录又是文件

临时节点,不能有子节点

znode节点变化的时候,可以出发事件

zookeeper 节点:znode

每个watcher 就是服务器集群中的一台机器

zookeeper 应用场景:

zk 保存Storm集群的所有数据

Storm集群：Zookeeper作为nimbus（master）和supervisor（slave）的中间枢纽，
保存Storm集群和作业的所有信息，并负责nimbus和supervisor的全部通信，
Fast faill 。

Zookeeper 作为master和slave之间唯一的通道,

消息提交到master上，master会把消息发送给zookeeper,zk在分发到每个slave

发布与订阅即所谓的配置管理，顾名思义就是将数据发布到zk节点上，供订阅者动态获取数据，
实现配置信息的集中式管理和动态更新。例如全局的配置信息，地址列表等就非常适合使用。

每天节点自动从zk获取

一个节点是全局唯一的path

zk 创建节点:

客户端访问:

redis01:/root# cd /zookeeper/server1
redis01:/zookeeper/server1# cd bin/
redis01:/zookeeper/server1/bin# ./zkCli.sh -server localhost:2181

2 ）创建一个新的 znode ，使用 create /zk myData 。这个命令创建了一个新的 znode 节点“ zk ”以及与它关联的字符串：

在leader 上创建: create /zk myData

会自动同步到所有服务器

在folloer上创建:也会同步到leader

一个节点上的数据发生变化后,通知其他节点

watch 监听节点变化

zk集群上相同的znode数据一定是相同的