5.1 常见命令行操作
常见操作。
启动客户端。
[wangzhou@zookeeper01 bin]$ ./zkCli.sh Connecting to localhost:2181 2022-04-05 07:37:54,764 [myid:] - INFO [main:Environment@109] - Client environment:zookeeper.version=3.5.7-f0fdd52973d373ffd9c86b81d99842dc2c7f660e, built on 02/10/2020 11:30 GMT ... WATCHER:: WatchedEvent state:SyncConnected type:None path:null [zk: localhost:2181(CONNECTED) 0]
不过，客户端连接的服务端是localhost,我们也可以通过： sh zkCli.sh -server host:port实现客户端与远程的服务端相连。
[zk: localhost:2181(CONNECTED) 0] quit [wangzhou@zookeeper01 bin]$ ./zkCli.sh -server zookeeper02:2181
在后续中，我们可以使用一台主机作为客户端、一台主机作为服务端。
查看帮助文档
[zk: zookeeper01:2181(CONNECTED) 0] help ZooKeeper -server host:port cmd args addauth scheme auth close config [-c] [-w] [-s] connect host:port create [-s] [-e] [-c] [-t ttl] path [data] [acl] delete [-v version] path deleteall path delquota [-n|-b] path get [-s] [-w] path getAcl [-s] path history listquota path ls [-s] [-w] [-R] path ls2 path [watch] printwatches on|off quit reconfig [-s] [-v version] [[-file path] | [-members serverID=host:port1:port2;port3[,...]*]] | [-add serverId=host:port1:port2;port3[,...]]* [-remove serverId[,...]*] redo cmdno removewatches path [-c|-d|-a] [-l] rmr path set [-s] [-v version] path data setAcl [-s] [-v version] [-R] path acl setquota -n|-b val path stat [-w] path sync path
我们重点学习里面增删改查节点信息的操作就可以了。
5.2 查看节点信息
先查看当前监听的服务端的节点信息看看。
[zk: zookeeper01:2181(CONNECTED) 1] ls / [zookeeper] [zk: zookeeper01:2181(CONNECTED) 2] ls -s / [zookeeper]cZxid = 0x0 ctime = Wed Dec 31 16:00:00 PST 1969 mZxid = 0x0 mtime = Wed Dec 31 16:00:00 PST 1969 pZxid = 0x0 cversion = -1 dataVersion = 0 aclVersion = 0 ephemeralOwner = 0x0 dataLength = 0 numChildren = 1
解释如下：
czxid：
创建节点的事务的zxid。
每次修改 ZooKeeper 状态都会产生一个 ZooKeeper 事务 ID。事务 ID 是 ZooKeeper 中所有修改总的次序。
ctime： znode 被创建的毫秒数（从 1970 年开始） mzxid： znode 最后更新的事务 zxid mtime： znode 最后修改的毫秒数（从 1970 年开始） pZxid： znode 最后更新的子节点 zxid cversion： znode 子节点变化号，znode 子节点修改次数 dataversion： znode 数据变化号 aclVersion： znode 访问控制列表的变化号 ephemeralOwner： 如果是临时节点，这个是 znode 拥有者的 session id。如果不是临时节点则是 0。 dataLength： znode 的数据长度 numChildren： znode 子节点数量
5.3 节点类型与对应操作
5.3.1 节点类型
注意，之前在讲集群时，节点指代的都是服务器主机节点。而这里只是znode下存放信息以节点形式进行组织，请读者注意区别
5.3.2 创建节点
创建永久节点
[zk: zookeeper01:2181(CONNECTED) 3] ls / [zookeeper] [zk: zookeeper01:2181(CONNECTED) 4] create /sanguo "lvbu" Created /sanguo [zk: zookeeper01:2181(CONNECTED) 5] ls / [sanguo, zookeeper] [zk: zookeeper01:2181(CONNECTED) 6] create /sanguo/shuguo "liubei" Created /sanguo/shuguo [zk: zookeeper01:2181(CONNECTED) 7] ls /sanguo [shuguo]
获取该节点信息
[zk: zookeeper01:2181(CONNECTED) 8] get -s /sanguo lvbu cZxid = 0x700000004 ctime = Tue Apr 05 08:02:45 PDT 2022 mZxid = 0x700000004 mtime = Tue Apr 05 08:02:45 PDT 2022 pZxid = 0x700000005 cversion = 1 dataVersion = 0 aclVersion = 0 ephemeralOwner = 0x0 dataLength = 4 numChildren = 1
创建带序列号的永久节点
[zk: zookeeper01:2181(CONNECTED) 10] create -s /sanguo/weiguo "caocao" Created /sanguo/weiguo0000000001 [zk: zookeeper01:2181(CONNECTED) 11] ls /sanguo [shuguo, weiguo0000000001] [zk: zookeeper01:2181(CONNECTED) 12] create -s /sanguo/weiguo "caocao" Created /sanguo/weiguo0000000002 [zk: zookeeper01:2181(CONNECTED) 13] ls /sanguo [shuguo, weiguo0000000001, weiguo0000000002]
创建临时节点。客户端重启后临时节点的信息会丢失
create -e /sanguo/wuguo"zhouyu"
修改节点值
[zk: zookeeper01:2181(CONNECTED) 15] set /sanguo/shuguo "zz" [zk: zookeeper01:2181(CONNECTED) 16] get -s /sanguo/shuguo zz cZxid = 0x700000005 ctime = Tue Apr 05 08:04:01 PDT 2022 mZxid = 0x700000008 mtime = Tue Apr 05 08:21:34 PDT 2022 pZxid = 0x700000005 cversion = 0 dataVersion = 1 aclVersion = 0 ephemeralOwner = 0x0 dataLength = 2 numChildren = 0
5.3.3 监听器原理
总结一句话就是，客户端在服务端进行注册，当客户端关心的数据发生变化，或者服务器节点上、下线了，服务端通过回调方法通知到客户端。其实现的方法其实就是观察者模式。如果读者不了解观察者模式，建议您阅读文章：从零开始学习Java设计模式 | 行为型模式篇：观察者模式_李阿昀的博客-CSDN博客，讲解的特别透彻了
[zk: zookeeper01:2181(CONNECTED) 17] get -w /sanguo lvbu [zk: zookeeper01:2181(CONNECTED) 18] set /sanguo zhubajie WATCHER:: WatchedEvent state:SyncConnected type:NodeDataChanged path:/sanguo
值得注意的是，只注册一次监听，只能监听一次节点信息的变化，下一次就不会通知了
