LeaderSelector

让所有 client 竞争，成功竞争成功（也就是获取锁）的就是 Leader

public class LeaderSelectorExample {
    public static void main(String[] args) throws Exception {
        List<CuratorFramework> clients = Lists.newArrayList();
        List<LeaderSelector> leaderSelectors = Lists.newArrayList();
        for (int i = 0; i < 10; i++) {
            CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1:2181", 5000, 5000, new RetryNTimes(3, 1000));
            clients.add(client);
            client.start();
            LeaderSelector leaderSelector = new LeaderSelector(client, "/leaderSelector", new LeaderSelectorListener() {
                @Override
                public void takeLeadership(CuratorFramework curatorFramework) throws Exception {
                    // 当 client 被选举为 leader 时，就会回调这个方法
                    // 利用锁来实现，让所有 client 竞争锁，也就是竞争 leader
                    System.out.println("当前的 Leader 是 = " + client);
                    // TODO
                    TimeUnit.SECONDS.sleep(5);
                }
                @Override
                public void stateChanged(CuratorFramework curatorFramework, ConnectionState connectionState) {
                }
            });
            leaderSelectors.add(leaderSelector);
            leaderSelector.start();
        }
        TimeUnit.SECONDS.sleep(5);
        System.out.println("按任意键退出...");
        System.in.read();
        for (LeaderSelector leaderSelector : leaderSelectors) {
            leaderSelector.close();
        }
        for (CuratorFramework client : clients) {
            client.close();
        }
    }
}

LeaderLatch

获取临时顺序节点中序号最小的值，就是 Leader

public class LeaderLatchExample {

    public static void main(String[] args) throws Exception {
        List<CuratorFramework> clients = Lists.newArrayList();
        List<LeaderLatch> leaderLatches = Lists.newArrayList();

        for (int i = 0; i < 10; i++) {
            CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1:2181", 5000, 5000, new RetryNTimes(3, 1000));
            clients.add(client);
            client.start();

            LeaderLatch leaderLatch = new LeaderLatch(client, "/leaderLatch", "leaderLatch#" + i);
            leaderLatches.add(leaderLatch);
            leaderLatch.start();
        }

        TimeUnit.SECONDS.sleep(5);

        // 获取临时顺序节点中序号最小的值，就是 Leader
        for (LeaderLatch leaderLatch : leaderLatches) {
            if (leaderLatch.hasLeadership()) {
                System.out.println("当前 Leader 是" + leaderLatch.getId());
                break;
            }
        }

        System.out.println("按任意键退出...");
        System.in.read();

        for (CuratorFramework client : clients) {
            client.close();
        }
    }
}