一种基于Orleans的分布式Id生成方案

public interface ISequenceNoGenerator : Orleans.IGrainWithIntegerKey
{
Task<Immutable<string>> GetNext();
}

public class SequenceNoGenerator : Orleans.Grain, ISequenceNoGenerator
{
private const int MaxSeed = 99999;
private int _seed = 0;
private int _currentSecondCounter = 0;
Task<Immutable<string>> ISequenceNoGenerator.GetNext()
{
var oldCounter = this._currentSecondCounter;

while (true)
{
this.UpdateCurrentTimestamp();

if (oldCounter != this._currentSecondCounter)
this._seed = 1;
else
{
++this._seed;
}

if (this._seed > MaxSeed) Task.Delay(100);
else break;
}

var seq = DateTime.Now.ToString("yyyyMMdd") + this._currentSecondCounter.ToString() + this._seed.ToString();
return Task.FromResult(seq.AsImmutable());
}

public override Task OnActivateAsync()
{
//延迟1秒启动，防止Activation在某个机器上崩溃后，在集群中其它host上启动时，sequenceNo在同一秒出现重复
Task.Delay(1000);

return base.OnActivateAsync();
}

private void UpdateCurrentTimestamp()
{
var currentTime = DateTime.Now;
var currentDayStart = Convert.ToDateTime(currentTime.ToShortDateString());
this._currentSecondCounter = (int)(new TimeSpan(currentTime.Ticks - currentDayStart.Ticks).TotalSeconds);
}
}