retry code

retry.cs

namespace Jobs {
  public static class Retry {
    static ILog log = LogManager.GetCurrentClassLogger();

    public static RetryPolicy Exponential(int retryCount, TimeSpan minBackoff, TimeSpan maxBackoff, TimeSpan deltaBackoff) {
      // Do any argument Pre-validation here, i.e. enforce max retry count etc. 
      return () => {
        return (int currentRetryCount, Exception lastException, out TimeSpan retryInterval) => {
          log.Info(m => m("currentRetryCount:{0},lastException:{1}", currentRetryCount, lastException));

          if (currentRetryCount < retryCount) {
            Random r = new Random();

            // Calculate Exponential backoff with +/- 20% tolerance
            int increment = (int)((Math.Pow(2, currentRetryCount) - 1) * r.Next((int)(deltaBackoff.TotalMilliseconds * 0.8), (int)(deltaBackoff.TotalMilliseconds * 1.2)));

            // Enforce backoff boundaries
            int timeToSleepMsec = (int)Math.Min(minBackoff.TotalMilliseconds + increment, maxBackoff.TotalMilliseconds);

            retryInterval = TimeSpan.FromMilliseconds(timeToSleepMsec);

            return true;
          }

          retryInterval = TimeSpan.Zero;
          return false;
        };
      };
    }
  }
}