test changes

Author: nhulston

internal/trace/listener.go

@@ -85,12 +85,40 @@ func (l *Listener) HandlerStarted(ctx context.Context, msg json.RawMessage) cont
 			serviceName = "aws.lambda"
 		}
 		extensionNotRunning := !l.extensionManager.IsExtensionRunning()
-		opts := append([]tracer.StartOption{
+
+		// Initialize base options
+		baseOpts := []tracer.StartOption{
 			tracer.WithService(serviceName),
 			tracer.WithLambdaMode(extensionNotRunning),
 			tracer.WithGlobalTag("_dd.origin", "lambda"),
 			tracer.WithSendRetries(2),
-		}, l.tracerOptions...)
+		}
+
+		// Read sampling rules from environment
+		samplingRulesStr := os.Getenv("DD_TRACE_SAMPLING_RULES")
+		if samplingRulesStr != "" {
+			logger.Debug(fmt.Sprintf("Found DD_TRACE_SAMPLING_RULES: %s", samplingRulesStr))
+			var rules []tracer.SamplingRule
+			if err := json.Unmarshal([]byte(samplingRulesStr), &rules); err != nil {
+				logger.Error(fmt.Errorf("Failed to parse DD_TRACE_SAMPLING_RULES: %v", err))
+			} else {
+				logger.Debug(fmt.Sprintf("Successfully parsed %d sampling rules", len(rules)))
+				// Convert the JSON rules to tracer.SamplingRule objects
+				var samplingRules []tracer.SamplingRule
+				for _, rule := range rules {
+					if rate, ok := rule["sample_rate"].(float64); ok {
+						samplingRules = append(samplingRules, tracer.RateRule(rate))
+					}
+				}
+				if len(samplingRules) > 0 {
+					baseOpts = append(baseOpts, tracer.WithSamplingRules(samplingRules))
+				}
+			}
+		}
+
+		// Merge base options with any user-provided options
+		opts := append(baseOpts, l.tracerOptions...)
+
 		if l.otelTracerEnabled {
 			provider := ddotel.NewTracerProvider(
 				opts...,