使用Zookeeper来为你的程序加上Leader Election的功能。
ZooKeeper是Hadoop的正式子项目，它是一个针对大型分布式系统的可靠协调系统，提供的功能包括：配置维护、名字服务、分布式同步、组服务等。ZooKeeper的目标就是封装好复杂易出错的关键服务，将简单易用的接口和性能高效、功能稳定的系统提供给用户。

废话不多说，

package com.ericsson.threef.zookeeper;import org.apache.zookeeper.*;import org.apache.zookeeper.data.Stat;import java.net.InetAddress;import java.net.UnknownHostException;import java.util.List;import java.util.concurrent.CountDownLatch;/** * Created by IntelliJ IDEA. * User: EDENYIN * Date: 1/4/11 * Time: 3:13 PM * To change this template use File | Settings | File Templates. */public class LeaderElection implements Watcher, Runnable {    private String zookeeperConnectionString;    private String rootPath;    private ZooKeeper zk;    private byte[] hostAddress;    public LeaderElection(String zookeeperConnectionString, String rootPath) {        this.zookeeperConnectionString = zookeeperConnectionString;        this.rootPath = rootPath;        try {            hostAddress = InetAddress.getLocalHost().getHostAddress().getBytes();        } catch (UnknownHostException e) {            e.printStackTrace();        }        buildZK();    }    private void buildZK() {        System.out.println("Build zk client");        try {            zk = new ZooKeeper(zookeeperConnectionString, 10000, this);            Stat s = zk.exists(rootPath, false);            if (s == null) {                zk.create(rootPath, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);                zk.create(rootPath + "/ELECTION", new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);            }            String value = zk.create(rootPath + "/ELECTION/n_", hostAddress, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);        } catch (Exception e) {            e.printStackTrace();            System.err.println("Error connect to zoo keeper");        }    }    public void process(WatchedEvent event) {        System.out.println(event);        if (event.getState() == Event.KeeperState.Disconnected || event.getState() == Event.KeeperState.Expired) {            System.out.println("Zookeeper connection timeout.");            buildZK();        }    }    public void run() {            while (true) {                try {                    List<String> children = zk.getChildren(rootPath + "/ELECTION", false);                    String leaderPath = "Not found";                    int minValue = -1;                    for (int i=0;i<children.size();i++) {                        String child = children.get(i);                        int index = Integer.parseInt(child.substring(2));                        if (i == 0) {                            minValue = index;                            leaderPath = child;                        }else if (index < minValue) {                            minValue = index;                            leaderPath = child;                        }                    }                    LatchChildWatcher latchChildWatcher = new LatchChildWatcher();                    byte[] data = zk.getData(rootPath + "/ELECTION/" + leaderPath, latchChildWatcher, null);                    System.out.println("find the leader on the path:" + leaderPath + " whose host address is " + new String(data));                    latchChildWatcher.await();                } catch (Exception e) {                    e.printStackTrace();                    System.err.println("Error get the leader." + e.getMessage());                }        }    }    private class LatchChildWatcher implements Watcher {        CountDownLatch latch;        public LatchChildWatcher(){            latch = new CountDownLatch(1);        }        public void process(WatchedEvent event){            System.out.println("Watcher fired on path: " + event.getPath() + " state: " +                    event.getState() + " type " + event.getType());            latch.countDown();        }        public void await() throws InterruptedException {            latch.await();        }    }}

附件是完整的maven项目。

Reference: http://hadoop.apache.org/zookeeper/docs/r3.3.1/recipes.html#sc_leaderElection