流水号设计（美团LeafSegment）

多线程生成流水号

设计思路

LeafSegment

关键代码

/// <summary>
/// 获取下一个Id
/// </summary>
/// <returns></returns>
public long NextId()
{
    lock (_lock)
    {
        long result = 0;

        //开启线程尝试获取数据
        _fill.Set();

        while (!_data.TryDequeue(out result))
        {
            //等待子线程
            _fillDone.WaitOne();
        }
        return result;
    }
}

private void Loop()
{
    (new Thread(_ =>
    {
        while (true)
        {
            _fill.WaitOne();

            if (FillData())
            {
                //通知主线程数据获取成功
                _fillDone.Set();
            }

        }
    })
    { IsBackground = true }).Start();
}

private bool FillData()
{
    bool isFill = false;
    //数量小于步长一半时触发拉新
    while (_data.Count < (_currentStep >> 1))
    {
        isFill = true;
        var segment = _increment.Invoke(_bizTag);
        _currentStep = segment.Step;
        for (var i = segment.MaxId - segment.Step + 1; i <= segment.MaxId; i++)
        {
            _data.Enqueue(i);
        }
    }
    return isFill;
}

性能测试

压测的两个请求：

[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
    private readonly IBusinessId _bussinessId;

    public ValuesController(IBusinessId businessId)
    {
        _bussinessId = businessId;
    }

    /// <summary>
    /// 获取流水号
    /// </summary>
    /// <param name="count"></param>
    /// <returns></returns>
    [HttpGet]
    public ActionResult<IEnumerable<string>> Get(int count)
    {
        return _bussinessId.GetMany("test_01", count);
    }


    /// <summary>
    /// 空请求
    /// </summary>
    /// <returns></returns>
    [HttpGet]
    [Route("test")]
    public ActionResult<int> Test()
    {
        return 1;
    }
}