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);
     }
 }