Address PR feedback: rename datadogTags to expectedDataTags, store ksr as primitive double

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: bm1549

dd-java-agent/instrumentation/opentelemetry/opentelemetry-0.3/src/test/groovy/OpenTelemetryTest.groovy

@@ -277,9 +277,9 @@ class OpenTelemetryTest extends InstrumentationSpecification {
       "-${DDSpanId.toHexStringPadded(spanId)}" +
       "-" + (propagatedPriority > 0 ? "01" : "00")
     def expectedTracestate = "dd=s:${propagatedPriority};p:${DDSpanId.toHexStringPadded(spanId)}"
-    def datadogTags = []
+    def expectedDataTags = []
     if (propagatedMechanism != UNKNOWN) {
-      datadogTags << "_dd.p.dm=-" + propagatedMechanism
+      expectedDataTags << "_dd.p.dm=-" + propagatedMechanism
       expectedTracestate += ";t.dm:-" + propagatedMechanism
     }
     if (traceId.toHighOrderLong() != 0) {
@@ -289,10 +289,10 @@ class OpenTelemetryTest extends InstrumentationSpecification {
       expectedTracestate += ";t.ksr:1"
     }
     if (traceId.toHighOrderLong() != 0) {
-      datadogTags << "_dd.p.tid=" + traceId.toHexStringPadded(32).substring(0, 16)
+      expectedDataTags << "_dd.p.tid=" + traceId.toHexStringPadded(32).substring(0, 16)
     }
     if (contextPriority == UNSET) {
-      datadogTags << "_dd.p.ksr=1"
+      expectedDataTags << "_dd.p.ksr=1"
     }
     def expectedTextMap = [
       "x-datadog-trace-id"         : "$traceId",
@@ -301,8 +301,8 @@ class OpenTelemetryTest extends InstrumentationSpecification {
       "traceparent"                : expectedTraceparent,
       "tracestate"                 : expectedTracestate,
     ]
-    if (!datadogTags.empty) {
-      expectedTextMap.put("x-datadog-tags", datadogTags.join(','))
+    if (!expectedDataTags.empty) {
+      expectedTextMap.put("x-datadog-tags", expectedDataTags.join(','))
     }
     textMap == expectedTextMap
 

dd-trace-core/src/main/java/datadog/trace/core/propagation/ptags/PTagsFactory.java

@@ -92,8 +92,7 @@ static class PTags extends PropagationTags {
     private volatile int traceSource;
     private volatile String debugPropagation;
 
-    // extracted Knuth sampling rate tag for easier updates
-    private volatile TagValue knuthSamplingRateTagValue;
+    private volatile double knuthSamplingRate = Double.NaN;
 
     // xDatadogTagsSize of the tagPairs, does not include the decision maker tag
     private volatile int xDatadogTagsSize = -1;
@@ -272,12 +271,11 @@ public String getDebugPropagation() {
 
     @Override
     public void updateKnuthSamplingRate(double rate) {
-      TagValue newValue = TagValue.from(formatKnuthSamplingRate(rate));
-      if (!Objects.equals(knuthSamplingRateTagValue, newValue)) {
+      if (Double.compare(knuthSamplingRate, rate) != 0) {
         clearCachedHeader(DATADOG);
         clearCachedHeader(W3C);
+        knuthSamplingRate = rate;
       }
-      knuthSamplingRateTagValue = newValue;
     }
 
     /** Formats a sampling rate with up to 6 significant digits and no trailing zeros. */
@@ -298,7 +296,8 @@ static String formatKnuthSamplingRate(double rate) {
     }
 
     TagValue getKnuthSamplingRateTagValue() {
-      return knuthSamplingRateTagValue;
+      double rate = knuthSamplingRate;
+      return Double.isNaN(rate) ? null : TagValue.from(formatKnuthSamplingRate(rate));
     }
 
     @Override
@@ -428,7 +427,7 @@ int getXDatadogTagsSize() {
         size = PTagsCodec.calcXDatadogTagsSize(size, TRACE_ID_TAG, traceIdHighOrderBitsHexTagValue);
         size =
             PTagsCodec.calcXDatadogTagsSize(
-                size, KNUTH_SAMPLING_RATE_TAG, knuthSamplingRateTagValue);
+                size, KNUTH_SAMPLING_RATE_TAG, getKnuthSamplingRateTagValue());
         int currentProductTraceSource = traceSource;
         if (currentProductTraceSource != ProductTraceSource.UNSET) {
           size =