ZooKeeper 实现分布式锁的方法示例

private const int CONNECTION_TIMEOUT = 50000;
private const string CONNECTION_STRING = "127.0.0.1:2181";
private ZooKeeper CreateClient()
{
	var zooKeeper = new ZooKeeper(CONNECTION_STRING, CONNECTION_TIMEOUT, NullWatcher.Instance);
	Stopwatch sw = new Stopwatch();
	sw.Start();
	while (sw.ElapsedMilliseconds < CONNECTION_TIMEOUT)
	{
		var state = zooKeeper.getState();
		if (state == ZooKeeper.States.CONNECTED || state == ZooKeeper.States.CONNECTING)
		{
			break;
		}
	}
	sw.Stop();
	return zooKeeper;
}

class NullWatcher : Watcher
  {
    public static readonly NullWatcher Instance = new NullWatcher();
    private NullWatcher() { }
    public override Task process(WatchedEvent @event)
    {
      return Task.CompletedTask;
    }
  }

/// <summary>
/// 加锁
/// </summary>
/// <param name="key">加锁的节点名</param>
/// <param name="lockAcquiredAction">加锁成功后需要执行的逻辑</param>
/// <param name="lockReleasedAction">锁释放后需要执行的逻辑，可为空</param>
/// <returns></returns>
public async Task Lock(string key, Action lockAcquiredAction, Action lockReleasedAction = null)
{
	// 获取 ZooKeeper Client
	ZooKeeper keeper = CreateClient();
	// 指定锁节点
	WriteLock writeLock = new WriteLock(keeper, $"/{key}", null);

	var lockCallback = new LockCallback(() =>
	{
		lockAcquiredAction.Invoke();
		writeLock.unlock();
	}, lockReleasedAction);
	// 绑定锁获取和释放的监听对象
	writeLock.setLockListener(lockCallback);
	// 获取锁（获取失败时会监听上一个临时节点）
	await writeLock.Lock();
}

class LockCallback : LockListener
{
	private readonly Action _lockAcquiredAction;
	private readonly Action _lockReleasedAction;

	public LockCallback(Action lockAcquiredAction, Action lockReleasedAction)
	{
		_lockAcquiredAction = lockAcquiredAction;
		_lockReleasedAction = lockReleasedAction;
	}

	/// <summary>
	/// 获取锁成功回调
	/// </summary>
	/// <returns></returns>
	public Task lockAcquired()
	{
		_lockAcquiredAction?.Invoke();
		return Task.FromResult(0);
	}

	/// <summary>
	/// 释放锁成功回调
	/// </summary>
	/// <returns></returns>
	public Task lockReleased()
	{
		_lockReleasedAction?.Invoke();
		return Task.FromResult(0);
	}
}

static async Task RunAsync()
{
	Parallel.For(1, 10, async (i) =>
	{
		await new ZooKeeprDistributedLock().Lock("locks", () =>
		{
			Console.WriteLine($"第{i}个请求,获取锁成功:{DateTime.Now},线程Id:{Thread.CurrentThread.ManagedThreadId}");
			Thread.Sleep(1000); // 业务逻辑...
		}, () =>
		{
			Console.WriteLine($"第{i}个请求,释放锁成功:{DateTime.Now},线程Id:{Thread.CurrentThread.ManagedThreadId}");
			Console.WriteLine("-------------------------------");
		});
	});
	await Task.CompletedTask;
}