0 課程地址
https://coding.imooc.com/lesson/201.html#mid=12735
1 重點關注
1.1 本節內容
curator使用監聽(無論改變多少次，只能監聽一次)
1.2 關鍵代碼
cto.client.getData().usingWatcher(new MyCuratorWatcher()).forPath(nodePath);
package com.imooc.curator; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; public class MyWatcher implements Watcher { @Override public void process(WatchedEvent event) { System.out.println("觸發watcher，節點路徑爲：" + event.getPath()); } }
2 課程內容
3 Coding
3.1 Curator使用監聽
- 啓動服務端
進入到
cd /usr/local/zookeeper/bin
重啓zookeeper服務端
./zkServer.sh restart
- 主類
package com.imooc.curator; import java.util.List; import org.apache.curator.RetryPolicy; import org.apache.curator.framework.CuratorFramework; import org.apache.curator.framework.CuratorFrameworkFactory; import org.apache.curator.framework.recipes.cache.ChildData; import org.apache.curator.framework.recipes.cache.PathChildrenCache; import org.apache.curator.framework.recipes.cache.PathChildrenCache.StartMode; import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent; import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener; import org.apache.curator.retry.RetryNTimes; import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.ZooDefs.Ids; import org.apache.zookeeper.data.Stat; public class CuratorOperator { public CuratorFramework client = null; public static final String zkServerPath = "172.26.139.4:2181"; /** * 實例化zk客戶端 */ public CuratorOperator() { /** * 同步創建zk示例，原生api是異步的 * * curator鏈接zookeeper的策略:ExponentialBackoffRetry * baseSleepTimeMs：初始sleep的時間 * maxRetries：最大重試次數 * maxSleepMs：最大重試時間 */ // RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 5); /** * curator鏈接zookeeper的策略:RetryNTimes * n：重試的次數 * sleepMsBetweenRetries：每次重試間隔的時間 */ RetryPolicy retryPolicy = new RetryNTimes(3, 5000); /** * curator鏈接zookeeper的策略:RetryOneTime * sleepMsBetweenRetry:每次重試間隔的時間 */ // RetryPolicy retryPolicy2 = new RetryOneTime(3000); /** * 永遠重試，不推薦使用 */ // RetryPolicy retryPolicy3 = new RetryForever(retryIntervalMs) /** * curator鏈接zookeeper的策略:RetryUntilElapsed * maxElapsedTimeMs:最大重試時間 * sleepMsBetweenRetries:每次重試間隔 * 重試時間超過maxElapsedTimeMs後，就不再重試 */ // RetryPolicy retryPolicy4 = new RetryUntilElapsed(2000, 3000); client = CuratorFrameworkFactory.builder() .connectString(zkServerPath) .sessionTimeoutMs(10000).retryPolicy(retryPolicy) .namespace("workspace").build(); client.start(); } /** * * @Description: 關閉zk客戶端連接 */ public void closeZKClient() { if (client != null) { this.client.close(); } } public static void main(String[] args) throws Exception { // 實例化 CuratorOperator cto = new CuratorOperator(); boolean isZkCuratorStarted = cto.client.isStarted(); System.out.println("當前客戶的狀態：" + (isZkCuratorStarted ? "連接中" : "已關閉")); // 創建節點 String nodePath = "/super/imooc"; // byte[] data = "superme".getBytes(); // cto.client.create().creatingParentsIfNeeded() // .withMode(CreateMode.PERSISTENT) // .withACL(Ids.OPEN_ACL_UNSAFE) // .forPath(nodePath, data); // 更新節點數據 // byte[] newData = "batman".getBytes(); // cto.client.setData().withVersion(0).forPath(nodePath, newData); // 刪除節點 // cto.client.delete() // .guaranteed() // 如果刪除失敗，那麼在後端還是繼續會刪除，直到成功 // .deletingChildrenIfNeeded() // 如果有子節點，就刪除 // .withVersion(0) // .forPath(nodePath); // 讀取節點數據 // Stat stat = new Stat(); // byte[] data = cto.client.getData().storingStatIn(stat).forPath(nodePath); // System.out.println("節點" + nodePath + "的數據爲: " + new String(data)); // System.out.println("該節點的版本號爲: " + stat.getVersion()); // 查詢子節點 // List<String> childNodes = cto.client.getChildren() // .forPath(nodePath); // System.out.println("開始打印子節點："); // for (String s : childNodes) { // System.out.println(s); // } // 判斷節點是否存在,如果不存在則爲空 // Stat statExist = cto.client.checkExists().forPath(nodePath + "/abc"); // System.out.println(statExist); // watcher 事件 當使用usingWatcher的時候，監聽只會觸發一次，監聽完畢後就銷燬 cto.client.getData().usingWatcher(new MyCuratorWatcher()).forPath(nodePath); // cto.client.getData().usingWatcher(new MyWatcher()).forPath(nodePath); // 爲節點添加watcher // NodeCache: 監聽數據節點的變更，會觸發事件 // final NodeCache nodeCache = new NodeCache(cto.client, nodePath); // // buildInitial : 初始化的時候獲取node的值並且緩存 // nodeCache.start(true); // if (nodeCache.getCurrentData() != null) { // System.out.println("節點初始化數據爲：" + new String(nodeCache.getCurrentData().getData())); // } else { // System.out.println("節點初始化數據爲空..."); // } // nodeCache.getListenable().addListener(new NodeCacheListener() { // public void nodeChanged() throws Exception { // if (nodeCache.getCurrentData() == null) { // System.out.println("空"); // return; // } // String data = new String(nodeCache.getCurrentData().getData()); // System.out.println("節點路徑：" + nodeCache.getCurrentData().getPath() + "數據：" + data); // } // }); // 爲子節點添加watcher // PathChildrenCache: 監聽數據節點的增刪改，會觸發事件 // String childNodePathCache = nodePath; // // cacheData: 設置緩存節點的數據狀態 // final PathChildrenCache childrenCache = new PathChildrenCache(cto.client, childNodePathCache, true); // /** // * StartMode: 初始化方式 // * POST_INITIALIZED_EVENT：異步初始化，初始化之後會觸發事件 // * NORMAL：異步初始化 // * BUILD_INITIAL_CACHE：同步初始化 // */ // childrenCache.start(StartMode.POST_INITIALIZED_EVENT); // // List<ChildData> childDataList = childrenCache.getCurrentData(); // System.out.println("當前數據節點的子節點數據列表："); // for (ChildData cd : childDataList) { // String childData = new String(cd.getData()); // System.out.println(childData); // } // // childrenCache.getListenable().addListener(new PathChildrenCacheListener() { // public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception { // if(event.getType().equals(PathChildrenCacheEvent.Type.INITIALIZED)){ // System.out.println("子節點初始化ok..."); // } // // else if(event.getType().equals(PathChildrenCacheEvent.Type.CHILD_ADDED)){ // String path = event.getData().getPath(); // if (path.equals(ADD_PATH)) { // System.out.println("添加子節點:" + event.getData().getPath()); // System.out.println("子節點數據:" + new String(event.getData().getData())); // } else if (path.equals("/super/imooc/e")) { // System.out.println("添加不正確..."); // } // // }else if(event.getType().equals(PathChildrenCacheEvent.Type.CHILD_REMOVED)){ // System.out.println("刪除子節點:" + event.getData().getPath()); // }else if(event.getType().equals(PathChildrenCacheEvent.Type.CHILD_UPDATED)){ // System.out.println("修改子節點路徑:" + event.getData().getPath()); // System.out.println("修改子節點數據:" + new String(event.getData().getData())); // } // } // }); Thread.sleep(100000); cto.closeZKClient(); boolean isZkCuratorStarted2 = cto.client.isStarted(); System.out.println("當前客戶的狀態：" + (isZkCuratorStarted2 ? "連接中" : "已關閉")); } public final static String ADD_PATH = "/super/imooc/d"; }
- watcher類
package com.imooc.curator; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; public class MyWatcher implements Watcher { @Override public void process(WatchedEvent event) { System.out.println("觸發watcher，節點路徑爲：" + event.getPath()); } }
- linux客戶端修改節點（修改多次）
--啓動linux客戶端 zkCli.sh [zk: localhost:2181(CONNECTED) 0] ls /workspace/super/imooc [a, b] --第一次修改 [zk: localhost:2181(CONNECTED) 1] set /workspace/super/imooc 56 cZxid = 0xd5 ctime = Sun Apr 07 06:26:23 CST 2024 mZxid = 0xe0 mtime = Mon Apr 08 06:39:55 CST 2024 pZxid = 0xd9 cversion = 2 dataVersion = 1 aclVersion = 0 ephemeralOwner = 0x0 dataLength = 2 numChildren = 2 --第2次修改 [zk: localhost:2181(CONNECTED) 2] set /workspace/super/imooc 56 cZxid = 0xd5 ctime = Sun Apr 07 06:26:23 CST 2024 mZxid = 0xe2 mtime = Mon Apr 08 06:40:12 CST 2024 pZxid = 0xd9 cversion = 2 dataVersion = 2 aclVersion = 0 ephemeralOwner = 0x0 dataLength = 2 numChildren = 2 --第3次修改 [zk: localhost:2181(CONNECTED) 3] set /workspace/super/imooc 56 cZxid = 0xd5 ctime = Sun Apr 07 06:26:23 CST 2024 mZxid = 0xe3 mtime = Mon Apr 08 06:40:16 CST 2024 pZxid = 0xd9 cversion = 2 dataVersion = 3 aclVersion = 0 ephemeralOwner = 0x0 dataLength = 2 numChildren = 2 [zk: localhost:2181(CONNECTED) 4]
- 打印日誌（只監聽一次）
2024-04-08 06:40:00,026 [main-SendThread(172.26.139.4:2181)] [org.apache.zookeeper.ClientCnxn$SendThread.logStartConnect(ClientCnxn.java:1035)] - [INFO] Opening socket connection to server 172.26.139.4/172.26.139.4:2181. Will not attempt to authenticate using SASL (unknown error) 2024-04-08 06:40:00,029 [main] [org.apache.curator.framework.imps.CuratorFrameworkImpl.start(CuratorFrameworkImpl.java:326)] - [INFO] Default schema 當前客戶的狀態：連接中 2024-04-08 06:40:00,033 [main-SendThread(172.26.139.4:2181)] [org.apache.zookeeper.ClientCnxn$SendThread.primeConnection(ClientCnxn.java:877)] - [INFO] Socket connection established to 172.26.139.4/172.26.139.4:2181, initiating session 2024-04-08 06:40:00,043 [main-SendThread(172.26.139.4:2181)] [org.apache.zookeeper.ClientCnxn$SendThread.onConnected(ClientCnxn.java:1302)] - [INFO] Session establishment complete on server 172.26.139.4/172.26.139.4:2181, sessionid = 0x1003feb17e70006, negotiated timeout = 10000 2024-04-08 06:40:00,051 [main-EventThread] [org.apache.curator.framework.state.ConnectionStateManager.postState(ConnectionStateManager.java:237)] - [INFO] State change: CONNECTED 觸發watcher，節點路徑爲：/super/imooc 2024-04-08 06:41:40,095 [Curator-Framework-0] [org.apache.curator.framework.imps.CuratorFrameworkImpl.backgroundOperationsLoop(CuratorFrameworkImpl.java:924)] - [INFO] backgroundOperationsLoop exiting 2024-04-08 06:41:40,108 [main] [org.apache.zookeeper.ZooKeeper.close(ZooKeeper.java:687)] - [INFO] Session: 0x1003feb17e70006 closed 當前客戶的狀態：已關閉