zookeeper分布式算法和部署

算法摘要
安装

####二阶段提交(Two-Phase Commit)
投票和执行
+ 协调者向参与者发送事务内容，询问是否可以提交，各参与者节点执行事务并向协调者反馈
+ 如果所有参与者反馈yes，那么提交事务；如果有no或者超时，中断事务回滚。参与者执行完操作后再向协调者发送ack消息；协调者收到ack消息，完

Paxos算法

提高分布式系统容错性的一致性算法

三个角色

Proposer（提案人），Acceptor（接收人），Learner（学习人）

一个提案被选定需要被半数以上的Acceptor接受

chubby的Quorum机制

过半机制

chubby分布式锁处理

锁延迟，如果锁因为异常情况被释放，chubby会为锁保留一定时间，类似自旋等待
锁序列器，锁的持有者向chubby请求一个锁序列器，包括锁名字，模式，序号，服务端检测验证

Zookeeper

所有机器通过选举确定Leader。Follower和Observer都能提供读服务，Observer机不参与Leader选举过程，也不参与过半写成功策略。

机器节点和数据节点

机器节点是集群中的机器，数据节点是数据模型中的数据单元-Znode，所有数据存储在内存中，数据模型就是一棵树Znode Tree

ZAB(Zookeeper Atomic Broadcast)原子广播协议

崩溃恢复（恢复模式下选举产生新的Leader）和消息广播，其中消息广播协议是基于具有FIFO特性的tcp协议来进行网络通信的，因此容易保证广播过程中消息接受与发送的顺序性

####安装单机伪分布式zk
```bash
cd /usr/local/src/
tar xvf zookeeper-3.4.11.tar.gz
mv zookeeper-3.4.11 ../zookeeper00
cd ../zookeeper00/
cd conf/
cp zoo_sample.cfg zoo.cfg

cd ../

mkdir {dataDir,dataLogDir}

cd dataDir/

vim myid # 配置该节点的id为1

cp zookeeper00 zookeeper01 -rf

cp zookeeper00 zookeeper02 -rf

<span id="config">

####节点1配置文件

其他节点修改clientPort端口号和dataDir，dataLogDir对应路径，创建对应的myid为2和3

```bash

[root@sjck-node03 conf]# cat 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=/usr/local/zookeeper00/dataDir

dataLogDir=/usr/local/zookeeper00/dataLogDir

# the port at which the clients will connect

clientPort=2181

# master

server.1=172.16.67.131:2888:3888

server.2=172.16.67.131:2889:3889

server.3=172.16.67.131:2890:3890

####简单集群zk监控脚本
```bash
[root@sjck-node03 zk]# cd /home/soft/zk/
[root@sjck-node03 zk]# cat start.sh
#!/bin/bash
/usr/local/zookeeper00/bin/zkServer.sh start
/usr/local/zookeeper01/bin/zkServer.sh start
/usr/local/zookeeper02/bin/zkServer.sh start
[root@sjck-node03 zk]# cat stop.sh
#!/bin/bash
/usr/local/zookeeper00/bin/zkServer.sh stop
/usr/local/zookeeper01/bin/zkServer.sh stop
/usr/local/zookeeper02/bin/zkServer.sh stop
[root@sjck-node03 zk]# cat checkzk.sh
#!/bin/bash
/usr/local/zookeeper00/bin/zkServer.sh status
/usr/local/zookeeper01/bin/zkServer.sh status
/usr/local/zookeeper02/bin/zkServer.sh status
```
####集群zk状态监控
```bash
[root@sjck-node03 zk]# sh start.sh
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper00/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper01/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper02/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@sjck-node03 zk]# sh checkzk.sh
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper00/bin/../conf/zoo.cfg
Mode: follower
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper01/bin/../conf/zoo.cfg
Mode: leader
ZooKeeper JMX enabled by default
Using config: /usr/local/zookeeper02/bin/../conf/zoo.cfg
Mode: follower
```
####常用监控命令
jps(Java Virtual Machine Process Status Tool)
查看java进程pid，-l输出完整package名，-v输出jvm参数
```bash
[root@sjck-node03 zk]# jps
7984 Jps
7746 QuorumPeerMain
7804 QuorumPeerMain
7773 QuorumPeerMain
```
####查看监听的端口
netstat -lntp |grep java

####连接
其他节点对应连接，2182，2183端口
```bash
[root@sjck-node03 bin]# ./zkCli.sh -server localhost:2181
```
####创建znode，其他节点连接查看数据是否同步
```bash
[zk: localhost:2181(CONNECTED) 0] create /data test-data
Created /data
[zk: localhost:2181(CONNECTED) 1] ls /
[zookeeper, data]
[zk: localhost:2181(CONNECTED) 2] get /data
```
####退出
```bash
[zk: localhost:2181(CONNECTED) 0] quit
```