I'm building an ASP.NET MVC site where I want to limit how often authenticated users can use some functions of the site.
Although I understand how rate-limiting works fundamentally, I can't visualize how to implement it programatically without creating a major code smell.
Can you point me towards a simple yet powerful solution for approaching such a problem, with C# sample code?
If it matters, all of these functions are currently expressed as Actions that only accept HTTP POST
. I may eventually want to implement rate-limiting for HTTP GET
functions as well, so I'm looking for a solution that works for all such circumstances.
If you are using IIS 7 you could take a look at the Dynamic IP Restrictions Extension. Another possibility is to implement this as an action filter:
[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
public class RateLimitAttribute : ActionFilterAttribute
{
public int Seconds { get; set; }
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
// Using the IP Address here as part of the key but you could modify
// and use the username if you are going to limit only authenticated users
// filterContext.HttpContext.User.Identity.Name
var key = string.Format("{0}-{1}-{2}",
filterContext.ActionDescriptor.ControllerDescriptor.ControllerName,
filterContext.ActionDescriptor.ActionName,
filterContext.HttpContext.Request.UserHostAddress
);
var allowExecute = false;
if (HttpRuntime.Cache[key] == null)
{
HttpRuntime.Cache.Add(key,
true,
null,
DateTime.Now.AddSeconds(Seconds),
Cache.NoSlidingExpiration,
CacheItemPriority.Low,
null);
allowExecute = true;
}
if (!allowExecute)
{
filterContext.Result = new ContentResult
{
Content = string.Format("You can call this every {0} seconds", Seconds)
};
filterContext.HttpContext.Response.StatusCode = (int)HttpStatusCode.Conflict;
}
}
}
And then decorate the action that needs to be limited:
[RateLimit(Seconds = 10)]
public ActionResult Index()
{
return View();
}