public async Task <RateLimitRecord> ProcessRequestAsync(RateLimitRecord rateRecord, RateLimitRule rule, DateTime currentTime, CancellationToken cancellationToken = default)
{
if (rateRecord != null)
{
// entry has not expired
if (rateRecord.Timestamp + rule.PeriodTimespan.Value >= currentTime)
{
// increment request count per rule's period
rateRecord.Count += 1;
}
else
{
var timeSpan = currentTime - rule.PeriodTimespan.Value;
IEnumerable <RequestLogRecord> records = await _requestLogRepository.GetByClientIdAsync(rateRecord.ClientId, cancellationToken, (req) => req.Timestamp > timeSpan);
rateRecord.Timestamp = records.First().Timestamp.Add(rule.PeriodTimespan.Value);
rateRecord.Count = records.Count() + 1;
}
}
else
{
rateRecord = new RateLimitRecord
{
Timestamp = DateTime.UtcNow,
Count = 1
};
}
//// stores: id (string) - timestamp (datetime) - total_requests (long)
await _counterRepository.UpdateOrAddCounterAsync(rateRecord.ClientId, rateRecord, cancellationToken);
return(rateRecord);
}
public async Task <RateLimitRecord> UpdateOrAddCounterAsync(string id, RateLimitRecord entry, CancellationToken cancellationToken = default)
{
return(await Task <RateLimitRecord> .Factory.StartNew(() =>
{
if (_records.ContainsKey(id))
{
_records[id] = entry;
return entry;
}
else
{
_records.Add(id, entry);
}
return entry;
}
));
}
// IMyScopedService is injected into Invoke
public async Task InvokeAsync(HttpContext context, IRateLimitService rateLimitService)
{
// check if rate limiting is enabled
if (_options == null)
{
await _next.Invoke(context);
return;
}
// compute identity from request
var identity = await ClientIdentityHelper.ResolveIdentityAsync(context, _options);
var currentTime = DateTime.UtcNow;
// check if user is already requested
var record = await rateLimitService.GetRateLimitRecordAsync(identity);
if (record == null)
{
record = new RateLimitRecord
{
ClientId = identity.ClientId,
Timestamp = currentTime
}
}
;
// check if user is blocked
if (record.isBlocked)
{
var blockTime = record.BlockedUntillTime - currentTime;
if (blockTime.TotalSeconds > 0)
{
await ReturnQuotaExceededResponse(context, record.BlockedUntillTime);
return;
}
else
{
//reset rateCounter record if time for block is run out
await rateLimitService.ResetUserAsync(identity, context.RequestAborted);
}
}
//find all rules eligibe for request
IEnumerable <RateLimitRule> rules = await rateLimitService.GetMatchingRulesAsync(identity, context.RequestAborted);
foreach (var rule in rules)
{
RateLimitRecord rateCounter = await rateLimitService.ProcessRequestAsync(record, rule, currentTime, context.RequestAborted);
if (rule.Limit > 0)
{
// check if limit is reached
if (rateCounter.Count > rule.Limit)
{
var blockedUser = await rateLimitService.BlockUserByRateLimitAsync(identity, rule);
// break execution
await ReturnQuotaExceededResponse(context, blockedUser.BlockedUntillTime);
return;
}
}
}
// Call the next delegate/middleware in the pipeline
await _next(context);
}
