zookeeper 实战操作

一：监听服务端zookeeper节点数据改变

import java.io.IOException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;

public class ConfigApp1 {
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        //连接zookeeper服务器
        ZooKeeper zk = new ZooKeeper("127.0.0.1:2181", 5000,
                new Watcher() {
                    public void process(WatchedEvent event) {
                        if (KeeperState.SyncConnected == event.getState()) {    //zk连接成功通知事件
                            if ( EventType.None == event.getType() && null == event.getPath() ) {
                                connectedSemaphore.countDown();
                                System.out.println("===========");
                            }
                        }

                    }
                });

        connectedSemaphore.await();
        //创建节点app1，不进行ACL权限控制，EPHEMERAL：临时节点
        zk.create("/app1", "app1Date".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);

        //注册对该节点的监听
        zk.exists("/app1", new WatcherClass(zk));

        //延迟2秒后 开始改变数据
        TimeUnit.SECONDS.sleep(2);
        for(int i = 0; i < 10; i++) {
            TimeUnit.SECONDS.sleep(1);
            String s = ("app" + i * 10);
            zk.setData("/app1", s.getBytes(), -1);
            System.out.println("数据改变了:"+s);
        }
        System.in.read();
    }

    static class WatcherClass implements Watcher {
        private ZooKeeper zk;

        public WatcherClass(ZooKeeper zk) {
            this.zk = zk;
        }

        @Override
        public void process(WatchedEvent arg0) {
            try {
                byte[] b = zk.getData("/app1", false, null);
                System.out.println("改变数据通知：" + new String(b));

                //获取数据后，再次对节点进行监听
                zk.exists("/app1", new WatcherClass(zk));
            } catch (KeeperException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }
}

console结果截图：

 二：集群管理

　　应用集群中，我们常常需要让每一个机器知道集群中（或依赖的其他某一个集群）哪些机器是活着的，并且在集群机器因为宕机，网络断链等原因能够不在人工介入的情况下迅速通知到每一个机器

思路：用三个类模拟成三个服务器，去连接zookeeper，这三个服务器监控zookeeper节点root，每个服务器上线都会在zookeeper的节点root下创建一个临时节点，这样，这三个服务器watcher这个zookeeper的root节点就可以动态感知服务器的上下线情况。

import java.io.IOException;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.data.Stat;
import org.apache.zookeeper.ZooKeeper;

public class Cluster1 {

    private static final int zkSessionTimeOut = 5000;

    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        //连接zookeeper服务器
        ZooKeeper zk = new ZooKeeper("127.0.0.1:2181", zkSessionTimeOut,
                new Watcher() {
                    public void process(WatchedEvent event) {
                        if (KeeperState.SyncConnected == event.getState()) {    //zk连接成功通知事件
                            if ( EventType.None == event.getType() && null == event.getPath() ) {
                                connectedSemaphore.countDown();
                                System.out.println("===========");
                            }
                        }

                    }
                });

        connectedSemaphore.await();

        Stat stat = zk.exists("/root", true);
         if(stat == null) {
             System.out.println("/root" + "路径不存在，请先创建该节点");
             //创建节点root，不进行ACL权限控制，PERSISTENTAL：永久节点  只有永久节点才可以创建子节点的临时节点
             zk.create("/root", "rootDate".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
         }
        String clusterPath = zk.create("/root/cluster1", "cluster1Date".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(clusterPath);

        ZkWatcher zkWatcher = new ZkWatcher(zk);
        List<String> clusterList = zk.getChildren("/root", zkWatcher);

        System.out.println("****************");
        for(String str : clusterList) {
            System.out.println("cluster:" + str);
        }
        System.out.println("****************");

        while(true) {

        }
    }

}

import java.io.IOException;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.data.Stat;

public class Cluster2 {

    private static final int zkSessionTimeOut = 5000;

    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        //连接zookeeper服务器
        ZooKeeper zk = new ZooKeeper("127.0.0.1:2181", zkSessionTimeOut,
                new Watcher() {
                    public void process(WatchedEvent event) {
                        if (KeeperState.SyncConnected == event.getState()) {    //zk连接成功通知事件
                            if ( EventType.None == event.getType() && null == event.getPath() ) {
                                connectedSemaphore.countDown();
                                System.out.println("===========");
                            }
                        }

                    }
                });

        connectedSemaphore.await();

        Stat stat = zk.exists("/root", true);
         if(stat == null) {
             System.out.println("/root" + "路径不存在，请先创建该节点");
             zk.create("/root", "rootDate".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
         }
        String clusterPath = zk.create("/root/cluster2", "cluster2Date".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(clusterPath);

        ZkWatcher zkWatcher = new ZkWatcher(zk);
        List<String> clusterList = zk.getChildren("/root", zkWatcher);

        System.out.println("****************");
        for(String str : clusterList) {
            System.out.println("cluster:" + str);
        }
        System.out.println("****************");

        while(true) {

        }
    }

}

import java.io.IOException;
import java.util.List;
import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;

public class Cluster3 {

    private static final int zkSessionTimeOut = 5000;

    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        //连接zookeeper服务器
        ZooKeeper zk = new ZooKeeper("127.0.0.1:2181", zkSessionTimeOut,
                new Watcher() {
                    public void process(WatchedEvent event) {
                        if (KeeperState.SyncConnected == event.getState()) {    //zk连接成功通知事件
                            if ( EventType.None == event.getType() && null == event.getPath() ) {
                                connectedSemaphore.countDown();
                                System.out.println("===========");
                            }
                        }

                    }
                });

        connectedSemaphore.await();

         Stat stat = zk.exists("/root", true);
         if(stat == null) {
             System.out.println("/root" + "路径不存在，请先创建该节点");
             zk.create("/root", "rootDate".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
         }
        String clusterPath = zk.create("/root/cluster3", "cluster3Date".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(clusterPath);

        ZkWatcher zkWatcher = new ZkWatcher(zk);
        List<String> clusterList = zk.getChildren("/root", zkWatcher);

        System.out.println("****************");
        for(String str : clusterList) {
            System.out.println("cluster:" + str);
        }
        System.out.println("****************");

        while(true) {

        }
    }

}

import java.util.List;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooKeeper;

public class ZkWatcher implements Watcher{

    private ZooKeeper zk;

    public ZkWatcher(ZooKeeper zk) {
        this.zk = zk;
    }

    @Override
    public void process(WatchedEvent event) {
        if(EventType.NodeChildrenChanged.equals(event.getType())) {
            List<String> clusterList = null;
            try {
                clusterList = zk.getChildren("/root", this);
            } catch (KeeperException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println("****************");
            System.out.println("changed");
            for(String str : clusterList) {
                System.out.println("cluster:" + str);
            }
            System.out.println("****************");
        }
    }

}