private void DeleteEmptyRequestsData(IClientIdentifier identifier)
{
if (_requests.ContainsKey(identifier) && _requests[identifier].Count == 0)
{
_requests.Remove(identifier);
}
}
private void UpdateRequestCount(IClientIdentifier identifier)
{
var expiryDate = _systemClock.UtcNow.Subtract(_configuration.RefreshRate);
_requestStore.DeleteRequestsOlderThan(identifier, expiryDate);
_requestStore.AddRequest(identifier, _systemClock.UtcNow);
}
public int NumberOfRequestsFor(IClientIdentifier identifier)
{
lock (_syncObject)
{
return(_requests.ContainsKey(identifier)
? _requests[identifier].Count
: 0);
}
}
public int RequestsRemaining(IClientIdentifier identifier)
{
UpdateRequestCount(identifier);
var numberOfRequests = GetNumberOfRequests(identifier);
var remaining = _configuration.Limit - numberOfRequests;
return(remaining);
}
public void DeleteRequestsOlderThan(IClientIdentifier identifier, DateTime expiryDate)
{
lock (_syncObject)
{
if (_requests.ContainsKey(identifier))
{
while (HasExpired(identifier, expiryDate))
{
_requests[identifier].Dequeue();
}
}
DeleteEmptyRequestsData(identifier);
}
}
public void AddRequest(IClientIdentifier identifier, DateTime dateTime)
{
lock (_syncObject)
{
if (!_requests.ContainsKey(identifier))
{
_requests.Add(identifier, new Queue <DateTime>(_maxNumberOfRequests));
}
if (_requests[identifier].Count == _maxNumberOfRequests)
{
_requests[identifier].Dequeue();
}
_requests[identifier].Enqueue(dateTime);
}
}
private bool HasExpired(IClientIdentifier identifier, DateTime expiryDate)
{
return(_requests[identifier].Count > 0 && _requests[identifier].Peek() < expiryDate);
}
private int GetNumberOfRequests(IClientIdentifier identifier)
{
return(_requestStore.NumberOfRequestsFor(identifier));
}
public async Task <RateLimitCacheEntry> CanAccessResource(string policyId, int limitPerHour, IClientIdentifier clientId)
{
var key = $"{policyId}:{clientId.IdentifierString}";
var existing = await _cache.GetJsonAsync <RateLimitCacheEntry>(key) ?? new RateLimitCacheEntry
{
Remaining = limitPerHour,
Resets = DateTime.UtcNow + TimeSpan.FromHours(1),
};
var updated = new RateLimitCacheEntry
{
Remaining = existing.Remaining - 1,
Resets = existing.Resets,
};
await _cache.SetJsonAsync(key, updated, new DistributedCacheEntryOptions
{
AbsoluteExpiration = new DateTimeOffset(updated.Resets, TimeSpan.Zero),
});
return(existing);
}
