private void AdjustWindowDynamic(int bytesConsumed, Http2Stream stream)
{
_deliveredBytes += bytesConsumed;
if (_deliveredBytes < StreamWindowThreshold)
{
return;
}
int windowUpdateIncrement = _deliveredBytes;
long currentTime = Stopwatch.GetTimestamp();
Http2Connection connection = stream.Connection;
TimeSpan rtt = connection._rttEstimator.MinRtt;
if (rtt > TimeSpan.Zero && _streamWindowSize < MaxStreamWindowSize)
{
TimeSpan dt = Stopwatch.GetElapsedTime(_lastWindowUpdate, currentTime);
// We are detecting bursts in the amount of data consumed within a single 'dt' window update period.
// The value "_deliveredBytes / dt" correlates with the bandwidth of the connection.
// We need to extend the window, if the bandwidth-delay product grows over the current window size.
// To enable empirical fine tuning, we apply a configurable multiplier (_windowScaleThresholdMultiplier) to the window size, which defaults to 1.0
//
// The condition to extend the window is:
// (_deliveredBytes / dt) * rtt > _streamWindowSize * _windowScaleThresholdMultiplier
//
// Which is reordered into the form below, to avoid the division:
if (_deliveredBytes * (double)rtt.Ticks > _streamWindowSize * dt.Ticks * WindowScaleThresholdMultiplier)
{
int extendedWindowSize = Math.Min(MaxStreamWindowSize, _streamWindowSize * 2);
windowUpdateIncrement += extendedWindowSize - _streamWindowSize;
_streamWindowSize = extendedWindowSize;
if (NetEventSource.Log.IsEnabled())
{
stream.Trace($"[FlowControl] Updated Stream Window. StreamWindowSize: {StreamWindowSize}, StreamWindowThreshold: {StreamWindowThreshold}");
}
Debug.Assert(_streamWindowSize <= MaxStreamWindowSize);
if (_streamWindowSize == MaxStreamWindowSize)
{
if (NetEventSource.Log.IsEnabled())
{
stream.Trace($"[FlowControl] StreamWindowSize reached the configured maximum of {MaxStreamWindowSize}.");
}
}
}
}
_deliveredBytes = 0;
Task sendWindowUpdateTask = connection.SendWindowUpdateAsync(stream.StreamId, windowUpdateIncrement);
connection.LogExceptions(sendWindowUpdateTask);
_lastWindowUpdate = currentTime;
}
public Http2StreamWindowManager(Http2Connection connection, Http2Stream stream)
{
HttpConnectionSettings settings = connection._pool.Settings;
_streamWindowSize = settings._initialHttp2StreamWindowSize;
_deliveredBytes = 0;
_lastWindowUpdate = default;
if (NetEventSource.Log.IsEnabled())
{
stream.Trace($"[FlowControl] InitialClientStreamWindowSize: {StreamWindowSize}, StreamWindowThreshold: {StreamWindowThreshold}, WindowScaleThresholdMultiplier: {WindowScaleThresholdMultiplier}");
}
}
