/// <summary>
/// Return the matched sampling rule name if the sampler finds one
/// and decide to sample. If no sampling rule matched, it falls back
/// to <see cref="LocalizedSamplingStrategy"/> "ShouldTrace" implementation.
/// All optional arguments are extracted from incoming requests by
/// X-Ray middleware to perform path based sampling.
/// </summary>
/// <param name="input">Instance of <see cref="SamplingInput"/>.</param>
/// <returns>Instance of <see cref="SamplingResponse"/>.</returns>
public SamplingResponse ShouldTrace(SamplingInput input)
{
if (!_isPollerStarted) // Start pollers lazily
{
Start();
}
if (string.IsNullOrEmpty(input.ServiceType))
{
input.ServiceType = AWSXRayRecorder.Instance.Origin;
}
TimeStamp time = TimeStamp.CurrentTime();
SamplingRule sampleRule = _ruleCache.GetMatchedRule(input, time);
if (sampleRule != null)
{
_logger.DebugFormat("Rule {0} is selected to make a sampling decision.", sampleRule.RuleName);
return(ProcessMatchedRule(sampleRule, time));
}
else
{
_logger.InfoFormat("No effective centralized sampling rule match. Fallback to local rules.");
return(_localFallbackRules.ShouldTrace(input));
}
}
/// <summary>
/// Returns matched rule for the given <see cref="SamplingInput"/>.
/// </summary>
/// <param name="input">Instance of <see cref="SamplingInput"/>.</param>
/// <param name="time">Current time.</param>
/// <returns>Instance of <see cref="SamplingRule"/>.</returns>
public SamplingRule GetMatchedRule(SamplingInput input, TimeStamp time)
{
if (IsExpired(time))
{
return(null);
}
SamplingRule matchedRule = null;
_cacheLock.EnterReadLock();
try
{
foreach (var item in _cache)
{
var rule = item.Value;
if (matchedRule != null)
{
break;
}
if (rule.Match(input) || rule.IsDefault())
{
matchedRule = rule;
}
}
}
finally
{
_cacheLock.ExitReadLock();
}
return(matchedRule);
}
/// <summary>
/// Determines whether or not this sampling rule applies to the incoming
/// request based on some of the request's parameters.
/// </summary>
/// <param name="input">Instance of <see cref="SamplingInput"/>.</param>
/// <returns>True if the rule matches.</returns>
internal bool Match(SamplingInput input)
{
try
{
return(StringExtension.IsMatch(input.ServiceName, ServiceName) && StringExtension.IsMatch(input.Method, HTTPMethod) && StringExtension.IsMatch(input.Url, URLPath) && StringExtension.IsMatch(input.Host, Host) && StringExtension.IsMatch(input.ServiceType, ServiceType));
}
catch (RegexMatchTimeoutException e)
{
_logger.Error(e, "Match rule timeout. Rule: serviceName = {0}, urlPath = {1}, httpMethod = {2}, host = {3}, serviceType = {4}. Input: serviceNameToMatch = {5}, urlPathToMatch = {6}, httpMethodToMatch = {7}, hostToMatch = {8}, serviceTypeToMatch = {9}.", ServiceName, URLPath,
HTTPMethod, Host, ServiceType, input.ServiceName, input.Url, input.Method, input.Host, input.ServiceType);
return(false);
}
}