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118 changes: 118 additions & 0 deletions
118
BccCode.Tripletex.Client/TripletexRateLimitingHandler.cs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| using System; | ||
| using System.Diagnostics; | ||
| using System.Linq; | ||
| using System.Net.Http; | ||
| using System.Threading; | ||
| using System.Threading.Tasks; | ||
|
|
||
| namespace BccCode.Tripletex.Client | ||
| { | ||
| public class TripletexRateLimitingHandler : DelegatingHandler | ||
| { | ||
| private static readonly SemaphoreSlim _semaphore = new SemaphoreSlim(1, 1); | ||
| private static int _remainingRequests = 100; | ||
| private static int _requestLimit = 100; | ||
| private static DateTimeOffset _resetTime = DateTimeOffset.MinValue; | ||
|
|
||
| private const int MAX_RETRIES = 10; | ||
| private const int RETRY_DELAY_MILLISECONDS = 500; | ||
|
|
||
| private const int QUOTA_DELAY_MILLISECONDS = 50; | ||
|
|
||
| public TripletexRateLimitingHandler(HttpMessageHandler innerHandler = null!) | ||
| : base(innerHandler ?? new HttpClientHandler()) | ||
| { | ||
| } | ||
|
|
||
| protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) | ||
| { | ||
| await WaitForQuotaAsync(cancellationToken); | ||
|
|
||
| HttpResponseMessage response = default!; | ||
| for (int retry = 0; retry < MAX_RETRIES; retry++) | ||
| { | ||
| response = await base.SendAsync(request, cancellationToken); | ||
| await UpdateRateLimitStateAsync(response); | ||
|
|
||
| if (response.StatusCode != System.Net.HttpStatusCode.TooManyRequests) | ||
| { | ||
| return response; | ||
| } | ||
|
|
||
| var retryAfter = RETRY_DELAY_MILLISECONDS; | ||
| if (response.Headers.TryGetValues("Retry-After", out var values) && int.TryParse(values.FirstOrDefault(), out var retryAfterValue)) | ||
| { | ||
| retryAfter = retryAfterValue * 1000; | ||
| } | ||
|
|
||
| Debug.WriteLine("Too many requests. Retrying after {0} milliseconds", retryAfter); | ||
| await System.Threading.Tasks.Task.Delay(retryAfter * retry, cancellationToken); | ||
| } | ||
|
|
||
| return response; // Return the last response after exhausting retries | ||
| } | ||
|
|
||
| private static async System.Threading.Tasks.Task WaitForQuotaAsync(CancellationToken cancellationToken) | ||
| { | ||
| while (true) | ||
| { | ||
| await _semaphore.WaitAsync(cancellationToken); | ||
| try | ||
| { | ||
| if (DateTimeOffset.Now >= _resetTime) | ||
| { | ||
| _remainingRequests = _requestLimit; // Reset to the new limit from headers | ||
| } | ||
|
|
||
| if (_remainingRequests > 0) | ||
| { | ||
| _remainingRequests--; | ||
| return; | ||
| } | ||
| } | ||
| finally | ||
| { | ||
| _semaphore.Release(); | ||
| } | ||
|
|
||
| var now = DateTimeOffset.Now; | ||
| if (_resetTime > now) | ||
| { | ||
| var timeUntilReset = _resetTime - now; | ||
|
|
||
| Debug.WriteLine("Quota exceeded, waiting until {0}", _resetTime); | ||
| await System.Threading.Tasks.Task.Delay(timeUntilReset, cancellationToken); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private static async System.Threading.Tasks.Task UpdateRateLimitStateAsync(HttpResponseMessage response) | ||
| { | ||
| await _semaphore.WaitAsync(); | ||
| try | ||
| { | ||
| if (response.Headers.TryGetValues("X-Rate-Limit-Limit", out var limitValues) && | ||
| int.TryParse(limitValues.FirstOrDefault(), out var limit)) | ||
| { | ||
| _requestLimit = limit; | ||
| } | ||
|
|
||
| if (response.Headers.TryGetValues("X-Rate-Limit-Remaining", out var remainingValues) && | ||
| int.TryParse(remainingValues.FirstOrDefault(), out var remaining)) | ||
| { | ||
| _remainingRequests = remaining; | ||
| } | ||
|
|
||
| if (response.Headers.TryGetValues("X-Rate-Limit-Reset", out var resetValues) && | ||
| int.TryParse(resetValues.FirstOrDefault(), out var resetSeconds)) | ||
| { | ||
| _resetTime = DateTimeOffset.Now.AddSeconds(resetSeconds); | ||
| } | ||
| } | ||
| finally | ||
| { | ||
| _semaphore.Release(); | ||
| } | ||
| } | ||
| } | ||
| } |