zookeeper应用

yonght

　　服务器端：监听zk上父节点的子节点变化

• 
  
  
  package monitor;
  import java.util.List;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.TimeUnit;
  import org.apache.zookeeper.CreateMode;
  import org.apache.zookeeper.WatchedEvent;
  import org.apache.zookeeper.Watcher;
  import org.apache.zookeeper.Watcher.Event.KeeperState;
  import org.apache.zookeeper.ZooDefs;
  import org.apache.zookeeper.ZooKeeper;
  /**
  * 监听客户端的上下线
  * @author lisg
  *
  */
  public class ServerMonitor {
  public static final String HOSTS = "vm1";
  private ZooKeeper zk = null;
  public static final String PARENT_PATH = "/monitor";
  private static int client_count = 0;
  public ServerMonitor() {
  final CountDownLatch cdl = new CountDownLatch(1);
  try {
  zk = new ZooKeeper(HOSTS, 5000, new Watcher() {
  @Override
  public void process(WatchedEvent event) {
  if(KeeperState.SyncConnected.equals(event.getState())) {
  cdl.countDown();
  }
  }
  });
  cdl.await();
  //创建父节点
  if(zk.exists(PARENT_PATH, false) == null) {
  zk.create(PARENT_PATH,
  "".getBytes(),
  ZooDefs.Ids.OPEN_ACL_UNSAFE,
  CreateMode.PERSISTENT);
  }
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
  public void run() {
  try {
  zk.getChildren(PARENT_PATH, new ClientChangeWatcher());
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
  class ClientChangeWatcher implements Watcher {
  @Override
  public void process(WatchedEvent event) {
  try {
  if(Event.EventType.NodeChildrenChanged.equals(event.getType())) {
  //获取子节点，同时注册监听
  final List<String> children = zk.getChildren(PARENT_PATH, this);
  if(client_count > children.size()) {
  System.out.println("有客户端下线");
  } else {
  System.out.println("有客户端上线");
  }
  client_count = children.size();
  }
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
  }
  public static void main(String[] args) {
  new ServerMonitor().run();
  try {
  TimeUnit.DAYS.sleep(1);
  } catch (InterruptedException e) {
  e.printStackTrace();
  }
  }
  }
  
  　　
  
  
• 
  

客户端：上线的时候在父节点上创建短暂的子节点




package monitor;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
/**
* 客户端
* 上线的时候在zk上创建一个短暂的子节点
* @author lisg
*
*/
public class Client {
public static final String CLIENT_PATH_PREFIX = "cli-";
public static void main(String[] args) {
final CountDownLatch cdl = new CountDownLatch(1);
try {
ZooKeeper zk = new ZooKeeper(ServerMonitor.HOSTS, 5000, new Watcher() {
@Override
public void process(WatchedEvent event) {
if(KeeperState.SyncConnected.equals(event.getState())) {
cdl.countDown();
}
}
});
cdl.await();
//创建父节点
zk.create(ServerMonitor.PARENT_PATH + "/" + CLIENT_PATH_PREFIX,
"".getBytes(),
Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
TimeUnit.SECONDS.sleep(5);
zk.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}

　　
　　



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