java – 如何有效地使用LeaderElection配方使用Zookeeper的策展人？

我正在使用Apache Curator图书馆在Zookeeper上进行领导选举.我的应用程序代码部署在各种机器中,我需要从一台机器执行我的代码,这就是为什么我在zookeeper上进行领导选举,以便我可以检查我是否是领导者,然后执行此代码.

以下是我的leaderElectionExecutor类,它确保每个应用程序都有一个策展人实例

public class leaderElectionExecutor {

    private ZookeeperClient zookClient;

    private static final String leader_NODE = "/testleader";

    private static class Holder {
        static final leaderElectionExecutor INSTANCE = new leaderElectionExecutor();
    }

    public static leaderElectionExecutor getInstance() {
        return Holder.INSTANCE;
    }

    private leaderElectionExecutor() {
        try {
            String hostname = Utils.getHostName();

            String nodes = "host1:2181,host2:2181;

            zookClient = new ZookeeperClient(nodes,leader_NODE,hostname);
            zookClient.start();

            // added sleep specifically for the leader to get selected
            // since I cannot call isleader method immediately after starting the latch
            TimeUnit.MINUTES.sleep(1);
        } catch (Exception ex) {
            // logging error
            System.exit(1);
        }
    }

    public ZookeeperClient getZookClient() {
        return zookClient;
    }
}

以下是我的ZookeeperClient代码 –

// can this class be improved in any ways?
public class ZookeeperClient {

    private CuratorFramework client;
    private String latchPath;
    private String id;
    private leaderLatch leaderLatch;

    public ZookeeperClient(String connString,String latchPath,String id) {
        client = CuratorFrameworkFactory.newClient(connString,new ExponentialBackoffRetry(1000,Integer.MAX_VALUE));
        this.id = id;
        this.latchPath = latchPath;
    }

    public void start() throws Exception {
        client.start();
        leaderLatch = new leaderLatch(client,latchPath,id);
        leaderLatch.start();
    }

    public boolean isleader() {
        return leaderLatch.hasleadership();
    }

    public Participant currentleader() throws Exception {
        return leaderLatch.getleader();
    }

    public void close() throws IOException {
        leaderLatch.close();
        client.close();
    }

    public CuratorFramework getClient() {
        return client;
    }

    public String getLatchPath() {
        return latchPath;
    }

    public String getId() {
        return id;
    }

    public leaderLatch getleaderLatch() {
        return leaderLatch;
    }
}

现在在我的应用程序中,我正在使用这样的代码 –

public void method01() {
    ZookeeperClient zookClient = leaderElectionExecutor.getInstance().getZookClient();
    if (zookClient.isleader()) {
        // do something
    }
}

public void method02() {
    ZookeeperClient zookClient = leaderElectionExecutor.getInstance().getZookClient();
    if (zookClient.isleader()) {
        // do something
    }
}

问题陈述：-

在策展人库中 – 调用isleader()在启动锁定后立即不起作用.领导选择需要时间.而且由于这个原因,我已经在我的leaderElectionExecutor代码中添加了1分钟的睡眠,但是我觉得这不是正确的方法.

有没有更好的办法呢？记住这一点,我需要一种方法来检查我是否是领导者,然后执行这段代码.我不能在一个方法中做所有事情,所以我需要调用来自不同类和方法的isleader方法来检查我是否是领导者,然后执行这段代码.

我正在使用Zookeeper 3.4.5和Curator 1.7.1版本.

解决方法

一旦我解决了一个非常类似于你的问题.这是我怎么做到的.

首先,我有我的对象由Spring管理.所以我有一个leaderLatch可以通过容器注入.使用leaderLatch的组件之一是leadershipwatcher,一个Runnable接口的实现,将领导事件发送到其他组件.这些最后一个组件是我命名为leadershipObserver的接口的实现. leadershipwatcher的实现主要是如下代码：

@Component
public class leadershipwatcher implements Runnable {
  private final leaderLatch leaderLatch;
  private final Collection<leadershipObserver> leadershipObservers;

  /* constructor with @Inject */

  @Override
  public void run() {
    try {
      leaderLatch.await();

      for (leadershipObserver observer : leadershipObservers) {
        observer.granted();
      }
    } catch (InterruptedException e) {
      for (leadershipObserver observer : leadershipObservers) {
        observer.interrupted();
      }
    }
  }
}

由于这只是一个草图,我建议您加强此代码,也许应用命令模式调用观察者,甚至将观察者提交到线程池,如果他们的作业阻塞或长时间运行cpu密集型任务.

原文地址：https://www.jb51.cc/java/123553.html