Zk學習筆記——建立節點
阿新 • • 發佈:2020-07-05
參考:從Paxos到Zookeeper分散式一致性原理和實踐
使用的zk依賴是cdh5.16.2的3.4.5
<!-- zookeeper --> <dependency> <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId> <version>3.4.5-cdh5.16.2</version> </dependency>
Zk在建立節點的有同步建立和非同步建立,但是Zk是不支援遞迴建立節點,即父節點必須儲存。
在建立同名的節點的時候,會丟擲NodeExistsException異常。
Zookeeper節點內容只支援位元組陣列(byte[])
程式碼,其中建立了一個永久節點,key是/app1,value是123
package com.bigdata.zookeeper; import org.apache.zookeeper.*; import java.util.concurrent.CountDownLatch; public class ZkExample implements Watcher { public static CountDownLatch connectedSemaphore = new CountDownLatch(1); public static void main(String[] args) throws Exception { ZooKeeper zk = new ZooKeeper("master:2181", 5000, new ZkExample()); System.out.println(zk.getState()); try { connectedSemaphore.await(); String path = zk.create("/app1", "123".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); System.out.println("success create znode: " + path); } catch (InterruptedException e) { System.out.println("Zk session established" + e); } } @Override public void process(WatchedEvent watchedEvent) { System.out.println(watchedEvent); if (Event.KeeperState.SyncConnected == watchedEvent.getState()) { connectedSemaphore.countDown(); } } }
輸出,使用Zkui檢視zk中的資料,能發現多出了/app1的節點,節點的值是123
Zk中節點的型別分為持久節點(PERSISTENT),持久順序節點(PERSISTENT_SEQUENTIAL),臨時節點(EPHEMERAL),臨時順序節點(EPHEMERAL_SEQUENTIAL)
區別如下