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3.2.3 节点类型(持久/短暂/有序号/无序号)
3.2.3.1 节点类型
持久(Persistent):客户端和服务器端断开连接后,创建的节点不删除
短暂(Ephemeral):客户端和服务器端断开连接后,创建的节点自己删除
说明:创建znode时设置顺序标识,znode名称后会附加一个值,顺序号是一个单调递增的计数器,由父节点维护
注意:在分布式系统中,顺序号可以被用于为所有的事件进行全局排序,这样客户端可以通过顺序号推断事件的顺序
(1)持久化目录节点客户端与Zookeeper断开连接后,该节点依旧存在 (2)持久化顺序编号目录节点客户端与Zookeeper断开连接后,该节点依旧存在,只是Zookeeper给该节点名称进行顺序编号 (3)临时目录节点客户端与Zookeeper断开连接后,该节点被删除 (4)临时顺序编号目录节点客户端与 Zookeeper 断开连接后 , 该节点被删除 , 只是Zookeeper给该节点名称进行顺序编号
3.2.3.2 分别创建2个普通节点(永久节点 + 不带序号)
[zk: hadoop102:2181(CONNECTED) 5] create /sanguo "simayi"
Created /sanguo
[zk: hadoop102:2181(CONNECTED) 6] ls /
[sanguo, zookeeper]
[zk: hadoop102:2181(CONNECTED) 7] create /sanguo/shuguo "liubei"
Created /sanguo/shuguo
注意:创建节点时,要赋值
3.2.3.3 获得节点的值
[zk: hadoop102:2181(CONNECTED) 10] get -s /sanguo/shuguo
liubei
cZxid = 0x300000009
ctime = Wed Dec 21 16:53:24 CST 2022
mZxid = 0x300000009
mtime = Wed Dec 21 16:53:24 CST 2022
pZxid = 0x300000009
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0
[zk: hadoop102:2181(CONNECTED) 4] get -s /sanguo
simayi
cZxid = 0x300000008
ctime = Wed Dec 21 16:53:09 CST 2022
mZxid = 0x300000008
mtime = Wed Dec 21 16:53:09 CST 2022
pZxid = 0x30000000f
cversion = 6
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 2
3.2.3.4 创建带序号的节点(永久节点 + 带序号)
(1)先创建一个普通的根节点/sanguo/weiguo
[zk: hadoop102:2181(CONNECTED) 1] create /sanguo/weiguo "caocao"
Created /sanguo/weiguo
(2)创建带序号的节点
[zk: hadoop102:2181(CONNECTED) 2] create -s /sanguo/weiguo/zhangliao "zhangliao"
Created /sanguo/weiguo/zhangliao0000000000
[zk: hadoop102:2181(CONNECTED) 3] create -s /sanguo/weiguo/zhangliao "zhangliao"
Created /sanguo/weiguo/zhangliao0000000001
[zk: hadoop102:2181(CONNECTED) 4] create -s /sanguo/weiguo/xuchu "xuchu"
Created /sanguo/weiguo/xuchu0000000002
如果原来没有序号节点,序号从0开始依次递增。如果原节点下已有2个节点,则再排序时从2开始,以此类推。
3.2.3.5 创建短暂节点(短暂节点 + 不带序号 or 带序号)
(1)创建短暂的不带序号的节点
[zk: hadoop102:2181(CONNECTED) 7] create -e /sanguo/wuguo "zhouyu"
Created /sanguo/wuguo
(2)创建短暂的带序号的节点
[zk: hadoop102:2181(CONNECTED) 2] create -e -s /sanguo/wuguo "zhouyu"
Created /sanguo/wuguo0000000001
(3)在当前客户端是能查看到的
[zk: hadoop102:2181(CONNECTED) 3] ls /sanguo
[wuguo, wuguo0000000001, shuguo]
(4)退出当前客户端然后再重启客户端
[zk: hadoop102:2181(CONNECTED) 12] quit
[summer@hadoop104 zookeeper-3.5.7]$ bin/zkCli.sh
(5)再次查看根目录下短暂节点已经删除
[zk: hadoop102:2181(CONNECTED) 0] ls /sanguo
[shuguo]
3.2.3.6 修改节点数据值
[zk: hadoop102:2181(CONNECTED) 6] set /sanguo/weiguo "simayi"