protected ListeningProbe()
{
_maxDataStoresPerSecond = null; // no data rate limit by default
_keepDeviceAwake = DefaultKeepDeviceAwake;
_deviceAwake = false;
_incomingDataRateCalculator = new DataRateCalculator(100);
// store all data to start with. we'll compute a store/drop rate after data have arrived.
_samplingModulus = 1;
_samplingModulusMatchAction = SamplingModulusMatchAction.Store;
}
public sealed override Task <bool> StoreDatumAsync(Datum datum, CancellationToken?cancellationToken = default(CancellationToken?))
{
bool store = true;
float maxDataStoresPerSecond = _maxDataStoresPerSecond.GetValueOrDefault(-1);
// 0 (or negligible) data per second: don't store. if max data per second is not set, the following inequality will be false.
if (Math.Abs(maxDataStoresPerSecond) < DATA_RATE_EPSILON)
{
store = false;
}
// non-negligible (or default -1) data per second: check data rate
else if (maxDataStoresPerSecond > 0)
{
_incomingDataRateCalculator.Add(datum);
// recalculate the sampling modulus after accumulating a full sample size in the data rate calculator
if ((_incomingDataRateCalculator.TotalAdded % _incomingDataRateCalculator.SampleSize) == 0)
{
double incomingDataPerSecond = _incomingDataRateCalculator.DataPerSecond;
double extraDataPerSecond = incomingDataPerSecond - maxDataStoresPerSecond;
// if we're not over the limit then store all samples
if (extraDataPerSecond <= 0)
{
_samplingModulus = 1;
_samplingModulusMatchAction = SamplingModulusMatchAction.Store;
}
// otherwise calculate a modulus that will get as close as possible to the desired rate given the empirical rate
else
{
double samplingModulusMatchRate = extraDataPerSecond / incomingDataPerSecond;
_samplingModulusMatchAction = SamplingModulusMatchAction.Drop;
if (samplingModulusMatchRate > 0.5)
{
samplingModulusMatchRate = 1 - samplingModulusMatchRate;
_samplingModulusMatchAction = SamplingModulusMatchAction.Store;
}
if (_samplingModulusMatchAction == SamplingModulusMatchAction.Store)
{
// round the (store) modulus down to oversample -- more is better, right?
_samplingModulus = (int)Math.Floor(1 / samplingModulusMatchRate);
}
else
{
// round the (drop) modulus up to oversample -- more is better, right?
_samplingModulus = (int)Math.Ceiling(1 / samplingModulusMatchRate);
}
}
}
bool isModulusMatch = (_incomingDataRateCalculator.TotalAdded % _samplingModulus) == 0;
if ((_samplingModulusMatchAction == SamplingModulusMatchAction.Store && !isModulusMatch) || (_samplingModulusMatchAction == SamplingModulusMatchAction.Drop && isModulusMatch))
{
store = false;
}
}
if (store)
{
return(base.StoreDatumAsync(datum, cancellationToken));
}
else
{
return(Task.FromResult(false));
}
}
