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Bound the 429 retry and back off exponentially #70

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Bound the 429 retry and back off exponentially #70

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33 changes: 29 additions & 4 deletions digicert-certcentral-caplugin/Client/CertCentralClient.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,14 @@ private CertCentralResponse Request(CertCentralBaseRequest request)

private static int RequestIDCounter = 1;

private const int MaxRateLimitRetries = 3;

private CertCentralResponse Request(CertCentralBaseRequest request, string parameters)
{
return Request(request, parameters, 1);
}

private CertCentralResponse Request(CertCentralBaseRequest request, string parameters, int attempt)
{
//set in config files
//ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
Expand Down Expand Up @@ -129,10 +136,28 @@ private CertCentralResponse Request(CertCentralBaseRequest request, string param
{
if (errorResponse.StatusCode == (HttpStatusCode)429/*Too Many Requests*/)
{
Logger.LogInformation($"Request ID: {reqID} was rate-limited. Trying again in 5 seconds");
// TODO - Figure out how long to wait, then wait that long
System.Threading.Thread.Sleep(5000);
return Request(request, parameters);
// DigiCert's documented limits are 1000 requests / 3 minutes AND 100 / 5
// seconds, rolling, per API key, and its guidance is exponential backoff
// with a default maximum of 3 retries. A fixed 5-second wait only ever
// clears the burst window, never the 3-minute one, and the retry was
// unbounded, so a genuine rate-limit became an endless 5-second poll with a
// growing stack rather than an error the caller could report.
if (attempt >= MaxRateLimitRetries)
{
Logger.LogWarning($"Request ID: {reqID} was rate-limited by DigiCert and has exhausted {MaxRateLimitRetries} attempts. Giving up.");
using (var limitReader = new StreamReader(errorResponse.GetResponseStream()))
{
oCertCertResponse.Success = false;
oCertCertResponse.Response = limitReader.ReadToEnd();
}
}
else
{
int waitSeconds = 5 * (int)Math.Pow(2, attempt - 1);
Logger.LogInformation($"Request ID: {reqID} was rate-limited. Retry {attempt} of {MaxRateLimitRetries - 1} in {waitSeconds} seconds");
System.Threading.Thread.Sleep(waitSeconds * 1000);
return Request(request, parameters, attempt + 1);
}
}
else
{
Expand Down