/// <summary>
/// Gets the request identity key.
/// </summary>
/// <returns>The request identity key.</returns>
/// <param name="requestIdentity">Request identity.</param>
private string GetRequestIdentityKey(RequestIdentity requestIdentity, CounterRule rule)
{
var key = $"{requestIdentity.HttpVerb}:{requestIdentity.Path}:{requestIdentity.ClientId}:{rule.Period}";
var idBytes = System.Text.Encoding.UTF8.GetBytes(key);
byte[] hashBytes;
using (var algorithm = System.Security.Cryptography.SHA1.Create())
{
hashBytes = algorithm.ComputeHash(idBytes);
}
return(BitConverter.ToString(hashBytes).Replace("-", string.Empty));
}
public RateLimitCounter Process(RequestIdentity requestIdentity, CounterRule rule)
{
var counter = new RateLimitCounter
{
Timestamp = DateTime.UtcNow,
TotalRequests = 1
};
var counterId = GetRequestIdentityKey(requestIdentity, rule);
// serial reads and writes
lock (_processLocker)
{
var entry = _store.Get(counterId);
if (entry.HasValue)
{
// entry has not expired
if (entry.Value.Timestamp.AddSeconds(rule.Period) >= DateTime.UtcNow)
{
// increment request count
var totalRequests = entry.Value.TotalRequests + 1;
// deep copy
counter = new RateLimitCounter
{
Timestamp = entry.Value.Timestamp,
TotalRequests = totalRequests
};
}
}
// stores: id (string) - timestamp (datetime) - total_requests (long)
_store.Set(counterId, counter, TimeSpan.FromSeconds(rule.Period));
}
return(counter);
}