Zookeeper学习（3）：基本操作

一、单节点操作

1. 启动服务器和client：

启动服务器
~# zkServer.sh start
ZooKeeper JMX enabled by default
Using config: /data/zookeeper/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
启动客户端
~# zkCli.sh

2. 查看当前所有节点

[zk: localhost:2181(CONNECTED) 0] ls -R /
# Zookeeper系统自带的节点
/
/zookeeper
/zookeeper/config
/zookeeper/quota

3. 新建app1和app2的znode

[zk: localhost:2181(CONNECTED) 1] create /app1
[zk: localhost:2181(CONNECTED) 1] create /app2
[zk: localhost:2181(CONNECTED) 1] create /app1/p_1
[zk: localhost:2181(CONNECTED) 1] create /app1/p_2
[zk: localhost:2181(CONNECTED) 1] create /app1/p_3

# 查看一下
[zk: localhost:2181(CONNECTED) 0] ls -R /
/
/app1
/app2
/zookeeper
/app1/p_1
/app1/p_2
/app1/p_3
/zookeeper/config
/zookeeper/quota

 

二、实现一个分布式锁

分布式锁要求如果锁的持有者宕了，锁可以被释放。ZooKeeper 的 ephemeral 节点恰好具备这样的特性。

 客户端1：创建一个临时znode（获取锁）

[zk: localhost:2181(CONNECTED) 6] create -e /lock
Created /lock

客户端2：这个时候也去创建一个相同znode（由于被锁定了，客户端2无法获取）

# 创建提示已经存在
[zk: localhost:2181(CONNECTED) 0] create -e /lock
Node already exists: /lock

# 监控该znode
[zk: localhost:2181(CONNECTED) 2] stat -w /lock
cZxid = 0xb
ctime = Thu May 19 09:13:48 EDT 2022
mZxid = 0xb
mtime = Thu May 19 09:13:48 EDT 2022
pZxid = 0xb
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x1074e5aa8bc0000
dataLength = 0
numChildren = 0

客户端1：退出客户端，由于是临时znode，断开链接之后会自动删除（释放锁）

[zk: localhost:2181(CONNECTED) 7] quit

WATCHER::

WatchedEvent state:Closed type:None path:null
2022-05-19 09:21:01,264 [myid:] - INFO  [main:ZooKeeper@1619] - Session: 0x1074e5aa8bc0000 closed
2022-05-19 09:21:01,266 [myid:] - ERROR [main:ServiceUtils@42] - Exiting JVM with code 0
2022-05-19 09:21:01,267 [myid:] - INFO  [main-EventThread:ClientCnxn$EventThread@578] - EventThread shut down for session: 0x1074e5aa8bc0000

客户端2：由于客户端2有监控这个znode，所以客户端1退出的时候，会收到日志，这个时候客户端2就可以创建了（获取锁）

WATCHER::

WatchedEvent state:SyncConnected type:NodeDeleted path:/lock

# 创建znode
[zk: localhost:2181(CONNECTED) 0] create -e /lock
Created /lock

　　

三、3节点quorum模式Zookeeper集群搭建 

节点1：

# 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/data1
# 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

## Metrics Providers
#
# https://prometheus.io Metrics Exporter
#metricsProvider.className=org.apache.zookeeper.metrics.prometheus.PrometheusMetricsProvider
#metricsProvider.httpPort=7000
#metricsProvider.exportJvmInfo=true

server.1=127.0.0.1:3333:3334
server.2=127.0.0.1:4444:4445
server.3=127.0.0.1:5555:5556

节点2：

# 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.存储位置需要修改
dataDir=/data/zookeeper/data2
# the port at which the clients will connect，端口修改下
clientPort=2182
# 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

## Metrics Providers
#
# https://prometheus.io Metrics Exporter
#metricsProvider.className=org.apache.zookeeper.metrics.prometheus.PrometheusMetricsProvider
#metricsProvider.httpPort=7000
#metricsProvider.exportJvmInfo=true

server.1=127.0.0.1:3333:3334
server.2=127.0.0.1:4444:4445
server.3=127.0.0.1:5555:5556

节点3：

# 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.存储位置需要修改
dataDir=/data/zookeeper/data3
# the port at which the clients will connect，端口修改下
clientPort=2183
# 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

## Metrics Providers
#
# https://prometheus.io Metrics Exporter
#metricsProvider.className=org.apache.zookeeper.metrics.prometheus.PrometheusMetricsProvider
#metricsProvider.httpPort=7000
#metricsProvider.exportJvmInfo=true

server.1=127.0.0.1:3333:3334
server.2=127.0.0.1:4444:4445
server.3=127.0.0.1:5555:5556　

启动集群：

zkServer.sh /data/zookeeper/conf/zoo-quorum-node1.cfg 
zkServer.sh /data/zookeeper/conf/zoo-quorum-node2.cfg 
zkServer.sh /data/zookeeper/conf/zoo-quorum-node3.cfg

连接集群：

zkCli.sh -server 127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183