ASP.NET MVC 3 中的每日调用率限制？

Question

我已经看到 Jarrod Dixon 的解决方案 (Best way to implement request throttling in ASP.NET MVC?) 用于实现每秒调用速率限制。我现在正试图弄清楚如何为每天 N-calls 构建一个类似的过滤器。

我正在构建一个开发者 API，其中免费帐户每天可获取约 100 次调用，而付费帐户可获得更高的速率限制。在 MVC 3 中限制每日调用次数的最佳方法是什么？

Answer 1

我认为内存结构在这里不够用，因为您需要测量很长的持续时间。在这种情况下，IIS 回收会出现问题。因此，我建议在数据库中记录用户对资源的访问，并且只允许在过去 24 小时内访问 100 次。

另一方面，这是我们实现的漏桶限制器（对于故障相对不重要的短期限制来说，这更方便）。使用 .NET 4 并发集合可能会改进此实现中的蛮力锁定：

public class RateLimiter
{
    private readonly double numItems;
    private readonly double ratePerSecond;
    private readonly Dictionary<object, RateInfo> rateTable = 
        new Dictionary<object, RateInfo>();
    private readonly object rateTableLock = new object();
    private readonly double timePeriod;

    public RateLimiter(double numItems, double timePeriod)
    {
        this.timePeriod = timePeriod;
        this.numItems = numItems;
        ratePerSecond = numItems / timePeriod;
    }

    public double Count
    {
        get
        {
            return numItems;
        }
    }

    public double Per
    {
        get
        {
            return timePeriod;
        }
    }

    public bool IsPermitted(object key)
    {
        RateInfo rateInfo;
        var permitted = true;
        var now = DateTime.UtcNow;
        lock (rateTableLock)
        {
            var expiredKeys = 
                rateTable
                .Where(kvp => 
                    (now - kvp.Value.LastCheckTime) 
                    > TimeSpan.FromSeconds(timePeriod))
                .Select(k => k.Key)
                .ToArray();
            foreach (var expiredKey in expiredKeys)
            {
                rateTable.Remove(expiredKey);
            }
            var dataExists = rateTable.TryGetValue(key,
                                                   out rateInfo);
            if (dataExists)
            {
                var timePassedSeconds = (now - rateInfo.LastCheckTime).TotalSeconds;
                var newAllowance = 
                     Math.Min(
                         rateInfo.Allowance 
                         + timePassedSeconds 
                         * ratePerSecond,
                         numItems);
                if (newAllowance < 1d)
                {
                    permitted = false;
                }
                else
                {
                    newAllowance -= 1d;
                }
                rateTable[key] = new RateInfo(now,
                                              newAllowance);
            }
            else
            {
                rateTable.Add(key,
                              new RateInfo(now,
                                           numItems - 1d));
            }

        }
        return permitted;
    }

    public void Reset(object key)
    {
        lock (rateTableLock)
        {
            rateTable.Remove(key);
        }
    }

    private struct RateInfo
    {
        private readonly double allowance;
        private readonly DateTime lastCheckTime;

        public RateInfo(DateTime lastCheckTime, double allowance)
        {
            this.lastCheckTime = lastCheckTime;
            this.allowance = allowance;
        }

        public DateTime LastCheckTime
        {
            get
            {
                return lastCheckTime;
            }
        }

        public double Allowance
        {
            get
            {
                return allowance;
            }
        }
    }

}