code.grnet.gr Git - pithos-ms-client/blob - trunk/hammock/src/net35/Hammock/Tasks/RateLimitingRule.cs

   1 using System;
   2
   3 namespace Hammock.Tasks
   4 {
   5 #if !SILVERLIGHT
   6     [Serializable]
   7 #endif
   8     public class RateLimitingRule<T> : IRateLimitingRule<T>
   9     {
  10         private readonly RateLimitType _rateLimitType;
  11
  12         public RateLimitingRule(Predicate<T> rateLimitIf)
  13         {
  14             _rateLimitType = RateLimitType.ByPredicate;
  15             RateLimitIf = rateLimitIf;
  16         }
  17
  18         public RateLimitingRule(double percentOfTotal)
  19         {
  20             _rateLimitType = RateLimitType.ByPercent;
  21             LimitToPercentOfTotal = percentOfTotal;
  22         }
  23
  24         public RateLimitingRule(Func<T> getRateLimitStatus, Predicate<T> rateLimitIf)
  25         {
  26             _rateLimitType = RateLimitType.ByPredicate;
  27             GetRateLimitStatus = getRateLimitStatus;
  28             RateLimitIf = rateLimitIf;
  29         }
  30
  31         public RateLimitingRule(Func<T> getRateLimitStatus, double percentOfTotal)
  32         {
  33             _rateLimitType = RateLimitType.ByPercent;
  34             GetRateLimitStatus = getRateLimitStatus;
  35             LimitToPercentOfTotal = percentOfTotal;
  36         }
  37
  38         #region IRateLimitingRule Members
  39
  40         public virtual double? LimitToPercentOfTotal { get; private set; }
  41         public virtual RateLimitType RateLimitType
  42         {
  43             get { return _rateLimitType; }
  44         }
  45
  46         public Func<T> GetRateLimitStatus { get; set; }
  47         public Predicate<T> RateLimitIf { get; private set; }
  48
  49         #endregion
  50
  51         public bool ShouldSkipForRateLimiting()
  52         {
  53             // [JD]: Only pre-skip via predicate; percentage based adjusts rate after the call
  54             if (RateLimitType != RateLimitType.ByPredicate)
  55             {
  56                 return false;
  57             }
  58
  59             if (RateLimitIf == null)
  60             {
  61                 throw new InvalidOperationException("Rule is set to use predicate, but no predicate is defined.");
  62             }
  63
  64             var status = default(T);
  65             if (GetRateLimitStatus != null)
  66             {
  67                 status = GetRateLimitStatus();
  68             }
  69             return !RateLimitIf(status);
  70         }
  71
  72         public TimeSpan? CalculateNewInterval()
  73         {
  74             if (RateLimitType != RateLimitType.ByPercent)
  75             {
  76                 return null;
  77             }
  78
  79             if (!LimitToPercentOfTotal.HasValue)
  80             {
  81                 return null;
  82             }
  83             var currentRateLimit = (IRateLimitStatus)GetRateLimitStatus();
  84             if (currentRateLimit.RemainingUses == 0)
  85             {
  86                 return currentRateLimit.NextReset - DateTime.Now;
  87             }
  88             var secondsUntilNextReset = (currentRateLimit.NextReset - DateTime.Now).TotalSeconds;
  89             var desiredRetriesBeforeReset = currentRateLimit.RemainingUses * LimitToPercentOfTotal.Value;
  90             var desiredInterval = (int)Math.Floor(secondsUntilNextReset / desiredRetriesBeforeReset);
  91             return new TimeSpan(0, 0, 0, desiredInterval);
  92         }
  93     }
  94 }