四 ZooKeeper常用命令行操作

  • 通过./zkCli.sh 打开zk的客户端进入命令行后台

    • ls/ls2 列出当前节点下的子节点 ls2还会列出当前节点的状态
    [zk: localhost:2181(CONNECTED) 5] ls2 /
[cluster, controller_epoch, brokers, zookeeper, admin, isr_change_notification, consumers, log_dir_event_notification, latest_producer_id_block, config]
cZxid = 0x0
ctime = Thu Jan 01 08:00:00 CST 1970
mZxid = 0x0
mtime = Thu Jan 01 08:00:00 CST 1970
pZxid = 0x4e
cversion = 14
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 0
numChildren = 10
    • get 与 stat命令
      • stat 列出节点状态 ls2相当于 ls + stat
    [zk: localhost:2181(CONNECTED) 6] stat /
cZxid = 0x0
ctime = Thu Jan 01 08:00:00 CST 1970
mZxid = 0x0
mtime = Thu Jan 01 08:00:00 CST 1970
pZxid = 0x4e
cversion = 14
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 0
numChildren = 10
    • get命令 获取节点内容和节点状态
    [zk: localhost:2181(CONNECTED) 8] get /zookeeper

cZxid = 0x0 #该节点创建（Create）时的id
ctime = Thu Jan 01 08:00:00 CST 1970
mZxid = 0x0 #该节点修改（Modify）后的id
mtime = Thu Jan 01 08:00:00 CST 1970
pZxid = 0x0 #子节点列表最后一次被修改的事务id
cversion = -1 #子节点的版本号
dataVersion = 0 #当前节点数据的版本号 节点数据改变时这个值会变化
aclVersion = 0  # 权限版本, 权限发生变化时版本号回发生变化
ephemeralOwner = 0x0
dataLength = 0 #数据长度
numChildren = 1 #子节点数量

4.2 zk特性 session的基本原理与create命令使用

  • 客户端与服务端之间的链接存在Session(会话)

  • 每个会话可以设置一个超时时间

  • 心跳机制: 客户端向服务端的ping包请求

  • 心跳结束, session则过期

  • Session过期, 则临时节点znode会被抛弃

  • create命令

    [zk: localhost:2181(CONNECTED) 10] create /czk czk-data #创建永久节点
Created /czk
[zk: localhost:2181(CONNECTED) 11] get /czk
czk-data
cZxid = 0x50
ctime = Sat Dec 29 17:17:53 CST 2018
mZxid = 0x50
mtime = Sat Dec 29 17:17:53 CST 2018
pZxid = 0x50
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 0
    • 创建临时节点 &session过期临时节点删除
    [zk: localhost:2181(CONNECTED) 12] create -e /itheima/tmp itheima-data
Created /itheima/tmp
[zk: localhost:2181(CONNECTED) 13] get /itheima
itheima-data
cZxid = 0x50
ctime = Sat Dec 29 17:17:53 CST 2018
mZxid = 0x50
mtime = Sat Dec 29 17:17:53 CST 2018
pZxid = 0x51
cversion = 1
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 12
numChildren = 1
    • 创建顺序节点
    [zk: localhost:2181(CONNECTED) 1] ls /itheima
[]
[zk: localhost:2181(CONNECTED) 2] create -s /itheima/sec seq
Created /itheima/sec0000000001
[zk: localhost:2181(CONNECTED) 3] create -s /itheima/sec seq
Created /itheima/sec0000000002
[zk: localhost:2181(CONNECTED) 4] ls /itheima
[sec0000000001, sec0000000002]

4.3 set/delete 命令

  • set命令:

     set path data [version] # set 路径 数据 [版本号]       []内为可选参数
    • 不传入版本号
    [zk: localhost:2181(CONNECTED) 17] get /czk
czk-data1
cZxid = 0x5b
ctime = Sat Dec 29 17:45:26 CST 2018
mZxid = 0x66
mtime = Sat Dec 29 18:00:12 CST 2018
pZxid = 0x65
cversion = 5
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 3
[zk: localhost:2181(CONNECTED) 18] set /czk czk-data2
cZxid = 0x5b
ctime = Sat Dec 29 17:45:26 CST 2018
mZxid = 0x67
mtime = Sat Dec 29 18:02:15 CST 2018
pZxid = 0x65
cversion = 5
dataVersion = 2
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 3
[zk: localhost:2181(CONNECTED) 19] get /czk
czk-data2
cZxid = 0x5b
ctime = Sat Dec 29 17:45:26 CST 2018
mZxid = 0x67
mtime = Sat Dec 29 18:02:15 CST 2018
pZxid = 0x65
cversion = 5
dataVersion = 2
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 3
    • 不传入版本号可能会有并发修改问题 可以通过指定版本号类似加锁功能
    [zk: localhost:2181(CONNECTED) 22] set /itheima itheima-data3 1
version No is not valid : /itheima  #版本不匹配 修改失败 当前版本2
[zk: localhost:2181(CONNECTED) 23] set /itheima itheima-data3 2
cZxid = 0x5b
ctime = Sat Dec 29 17:45:26 CST 2018
mZxid = 0x69
mtime = Sat Dec 29 18:29:21 CST 2018
pZxid = 0x65
cversion = 5
dataVersion = 3
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 3
[zk: localhost:2181(CONNECTED) 24] get /itheima
itheima-data3
cZxid = 0x5b
ctime = Sat Dec 29 17:45:26 CST 2018
mZxid = 0x69
mtime = Sat Dec 29 18:29:21 CST 2018
pZxid = 0x65
cversion = 5
dataVersion = 3
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 13
numChildren = 3
    • delete 命令: delete path [version]
    [zk: localhost:2181(CONNECTED) 25] ls /itheima
[sec0000000003, sec0000000001, sec0000000002]
[zk: localhost:2181(CONNECTED) 27] delete /itheima/sec000000000
sec0000000003   sec0000000001   sec0000000002
[zk: localhost:2181(CONNECTED) 27] delete /itheima/sec0000000001
[zk: localhost:2181(CONNECTED) 28] ls /itheima
[sec0000000003, sec0000000002]
[zk: localhost:2181(CONNECTED) 29] set /itheima/sec000000000
sec0000000003   sec0000000002
[zk: localhost:2181(CONNECTED) 29] set /itheima/sec0000000002 test2
cZxid = 0x64
ctime = Sat Dec 29 17:49:38 CST 2018
mZxid = 0x6b
mtime = Sat Dec 29 18:54:33 CST 2018
pZxid = 0x64
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0
[zk: localhost:2181(CONNECTED) 30] delete /itheima/sec000000000
sec0000000003   sec0000000002
[zk: localhost:2181(CONNECTED) 30] delete /itheima/sec0000000002 0
version No is not valid : /itheima/sec0000000002

  • 总结 使用set / delete命令的时候尽量使用版本号 避免误操作

4.4 watcher机制

  • 针对每个节点的操作, 都会有一个监督者->watcher

  • 当监控的某个对象(znode)发生了变化, 则触发watcher事件

  • zk中的watcher是一次性的, 触发后立即销毁

  • 父节点, 子节点增删改都能触发其watcher

  • 针对不同类型的操作, 触发的watcher事件也不同:

    • (子)节点创建事件
    • (子)节点删除事件
    • (子)节点数据变化事件

  • watcher命令行

    • 通过get path [watch]设置watcher
    • 父节点 增 删 改操作触发 watcher
    • 子节点 增 删 改操作触发 watcher

  • 创建父节点触发: NodeCreated

    • stat path [watch]
    [zk: localhost:2181(CONNECTED) 33] stat /itcast watch
Node does not exist: /itcast
[zk: localhost:2181(CONNECTED) 35] create /itcast 123

WATCHER::Created /itcast


WatchedEvent state:SyncConnected type:NodeCreated path:/itcast
    • get path [watch]
    [zk: localhost:2181(CONNECTED) 36] get /itcast watch
123
cZxid = 0x6d
ctime = Sat Dec 29 19:43:13 CST 2018
mZxid = 0x6d
mtime = Sat Dec 29 19:43:13 CST 2018
pZxid = 0x6d
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 3
numChildren = 0
[zk: localhost:2181(CONNECTED) 37] set /itcast 789

WATCHER::

WatchedEvent state:SyncConnected type:NodeDataChanged path:/itcast
cZxid = 0x6d
ctime = Sat Dec 29 19:43:13 CST 2018
mZxid = 0x6e
mtime = Sat Dec 29 19:47:24 CST 2018
pZxid = 0x6d
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 3
numChildren = 0
    • ls/ls2 path [watch]
    [zk: localhost:2181(CONNECTED) 38] ls /itcast watch
[]
[zk: localhost:2181(CONNECTED) 39] delete /itcast

WATCHER::

WatchedEvent state:SyncConnected type:NodeDeleted path:/itcast

  • ls为父节点设置watcher, 创建子节点触发:NodeChildrenChanged

  • ls为父节点设置watcher, 删除子节点触发:NodeChildrenChanged

  • ls为父节点设置watcher, 修改子节点不触发事件

    [zk: localhost:2181(CONNECTED) 49] ls /itheima watch
[sec0000000003, dir1, sec0000000002]
[zk: localhost:2181(CONNECTED) 51] create /itheima/dir2 123

WATCHER::Created /itheima/dir2


WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/itheima
[zk: localhost:2181(CONNECTED) 52] ls /itheima watch
[sec0000000003, dir2, dir1, sec0000000002]
[zk: localhost:2181(CONNECTED) 53] delete /itheima/dir2

WATCHER::

WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/itheima
[zk: localhost:2181(CONNECTED) 54]

  • watcher 使用场景

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