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The following page has been changed by BenjaminReed: http://wiki.apache.org/hadoop/ZooKeeper/ZooKeeperExercise1 New page: Let's start off by creating a minimal ZooKeeper client: {{{ import java.io.*; import org.apache.zookeeper.*; public class SimpleZoo { static class MyWatcher implements Watcher { public void process(WatchedEvent event) { System.err.println(event); } } public static void main(String[] args) throws Exception { MyWatcher myWatcher = new MyWatcher(); ZooKeeper zk = new ZooKeeper(args[0], 10000, myWatcher); Thread.sleep(10000); zk.close(); } } }}} What events do you get when you start? Lets create a program to create a znode (I'll use "/motd", but you can pick your own name). You'll need to add: {{{ zk.create("/motd", "hi".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); }}} What happens if you try to create /motd twice? Create a new simple client to set "/motd": {{{ zk.setData("/motd", newdata, -1); }}} Create a new simple client to read "/motd". {{{ Stat stat = new Stat(); byte data[] = zk.getData("/motd", true, stat); }}} Try changing /data and watch the events you get. What if you change /data twice in a row? Could this be used for messaging?
