private static SampleDecision ApplyRule(SamplingRule rule)
{
if (rule.RateLimiter.Request())
{
return(SampleDecision.Sampled);
}
return(ThreadSafeRandom.NextDouble() <= rule.Rate ? SampleDecision.Sampled : SampleDecision.NotSampled);
}
/// <summary>
/// Use X-Ray client to get the sampling rules
/// from X-Ray service.The call is proxied and signed by X-Ray Daemon.
/// </summary>
/// <returns></returns>
public async Task <GetSamplingRulesResponse> GetSamplingRules()
{
List <SamplingRule> newRules = new List <SamplingRule>();
GetSamplingRulesRequest request = new GetSamplingRulesRequest();
var response = await _xrayClient.GetSamplingRulesAsync(request);
foreach (var record in response.SamplingRuleRecords)
{
var rule = record.SamplingRule;
if (rule.Version == Version && SamplingRule.IsValid(rule)) // We currently only handle v1 sampling rules.
{
var sampleRule = new SamplingRule(rule.RuleName, rule.Priority, rule.FixedRate, rule.ReservoirSize, rule.Host, rule.ServiceName, rule.HTTPMethod, rule.URLPath, rule.ServiceType, rule.ResourceARN, rule.Attributes);
newRules.Add(sampleRule);
}
}
GetSamplingRulesResponse result = new GetSamplingRulesResponse(newRules);
return(result);
}
private SamplingResponse ProcessMatchedRule(SamplingRule sampleRule, TimeStamp time)
{
bool shouldSample = true;
Reservoir reservoir = sampleRule.Reservoir;
SamplingResponse sampleResult = null;
sampleRule.IncrementRequestCount(); // increment request counter for matched rule
ReservoirDecision reservoirDecision = reservoir.BorrowOrTake(time, sampleRule.CanBorrow); // check if we can borrow or take from reservoir
if (reservoirDecision == ReservoirDecision.Borrow)
{
sampleRule.IncrementBorrowCount();
}
else if (reservoirDecision == ReservoirDecision.Take)
{
sampleRule.IncrementSampledCount();
}
else if (ThreadSafeRandom.NextDouble() <= sampleRule.GetRate()) // compute based on fixed rate
{
sampleRule.IncrementSampledCount();
}
else
{
shouldSample = false;
}
if (shouldSample)
{
sampleResult = new SamplingResponse(sampleRule.RuleName, SampleDecision.Sampled);
}
else
{
sampleResult = new SamplingResponse(SampleDecision.NotSampled);
}
return(sampleResult);
}
