Here's a generic version of what we've been using on Stack Overflow for the past year:
/// <summary>
/// Decorates any MVC route that needs to have client requests limited by time.
/// </summary>
/// <remarks>
/// Uses the current System.Web.Caching.Cache to store each client request to the decorated route.
/// </remarks>
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
public class ThrottleAttribute : ActionFilterAttribute
{
/// <summary>
/// A unique name for this Throttle.
/// </summary>
/// <remarks>
/// We'll be inserting a Cache record based on this name and client IP, e.g. "Name-192.168.0.1"
/// </remarks>
public string Name { get; set; }
/// <summary>
/// The number of seconds clients must wait before executing this decorated route again.
/// </summary>
public int Seconds { get; set; }
/// <summary>
/// A text message that will be sent to the client upon throttling. You can include the token {n} to
/// show this.Seconds in the message, e.g. "Wait {n} seconds before trying again".
/// </summary>
public string Message { get; set; }
public override void OnActionExecuting(ActionExecutingContext c)
{
var key = string.Concat(Name, "-", c.HttpContext.Request.UserHostAddress);
var allowExecute = false;
if (HttpRuntime.Cache[key] == null)
{
HttpRuntime.Cache.Add(key,
true, // is this the smallest data we can have?
null, // no dependencies
DateTime.Now.AddSeconds(Seconds), // absolute expiration
Cache.NoSlidingExpiration,
CacheItemPriority.Low,
null); // no callback
allowExecute = true;
}
if (!allowExecute)
{
if (String.IsNullOrEmpty(Message))
Message = "You may only perform this action every {n} seconds.";
c.Result = new ContentResult { Content = Message.Replace("{n}", Seconds.ToString()) };
// see 409 - http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
c.HttpContext.Response.StatusCode = (int)HttpStatusCode.Conflict;
}
}
}
Sample usage:
[Throttle(Name="TestThrottle", Message = "You must wait {n} seconds before accessing this url again.", Seconds = 5)]
public ActionResult TestThrottle()
{
return Content("TestThrottle executed");
}
The ASP.NET Cache works like a champ here - by using it, you get automatic clean-up of your throttle entries. And with our growing traffic, we're not seeing that this is an issue on the server.
Feel free to give feedback on this method; when we make Stack Overflow better, you get your Ewok fix even faster :)