/// <summary>
/// Initializes a new instance of the <see cref="ThrottlingSentinelAttribute"/> class.
/// </summary>
/// <param name="rateLimit">The allowed rate from within a given <paramref name="window"/>.</param>
/// <param name="window">The duration of the window.</param>
/// <param name="windowUnit">One of the enumeration values that specifies the time unit of <paramref name="window"/>.</param>
public ThrottlingSentinelAttribute(int rateLimit, double window, TimeUnit windowUnit)
{
var options = new ThrottlingSentinelOptions();
RateLimit = rateLimit;
Window = window;
WindowUnit = windowUnit;
UseRetryAfterHeader = options.UseRetryAfterHeader;
RetryAfterHeader = options.RetryAfterHeader;
TooManyRequestsMessage = options.TooManyRequestsMessage;
RateLimitHeaderName = options.RateLimitHeaderName;
RateLimitRemainingHeaderName = options.RateLimitRemainingHeaderName;
RateLimitResetHeaderName = options.RateLimitResetHeaderName;
}
public static async Task InvokeThrottlerSentinelAsync(HttpContext context, IThrottlingCache tc, ThrottlingSentinelOptions options, Action <HttpResponseMessage, HttpResponse> transformer)
{
var utcNow = DateTime.UtcNow;
var throttlingContext = options.ContextResolver?.Invoke(context);
if (!throttlingContext.IsNullOrWhiteSpace())
{
try
{
await ThrottleLocker.WaitAsync();
if (!tc.TryGetValue(throttlingContext, out var tr))
{
tr = new ThrottleRequest(options.Quota);
tc.AddIfNotContainsKey(throttlingContext, tr);
}
else
{
tr.Refresh();
tr.Total++;
}
var window = new TimeRange(utcNow, tr.Expires);
var delta = window.Duration;
var reset = utcNow.Add(delta);
context.Response.Headers.AddOrUpdate(options.RateLimitHeaderName, tr.Quota.RateLimit.ToString(CultureInfo.InvariantCulture));
context.Response.Headers.AddOrUpdate(options.RateLimitRemainingHeaderName, Math.Max(tr.Quota.RateLimit - tr.Total, 0).ToString(CultureInfo.InvariantCulture));
context.Response.Headers.AddOrUpdate(options.RateLimitResetHeaderName, reset.ToEpochTime().ToString(CultureInfo.InvariantCulture));
if (tr.Total > tr.Quota.RateLimit && tr.Expires > utcNow)
{
var message = options.ResponseBroker?.Invoke(delta, reset);
if (message != null)
{
message.ToHttpResponse(context.Response, transformer);
throw new ThrottlingException((int)message.StatusCode, await message.Content.ReadAsStringAsync(), tr.Quota.RateLimit, delta, reset);
}
}
tc[throttlingContext] = tr;
}
finally
{
ThrottleLocker.Release();
}
}
}
