Do not allocate a tracing context when not fully extracted (#9693)

* OTEL: don't return a span if not valid

* suggestions

* feat(otel): Improving test

Moving missing trace context to a dedicated test (not dependent on other propagation style as it concerns tracecontext only).
Adding more tests related to Span.fromContextOrNull() on span activation test suite.

---------

Co-authored-by: Bruce Bujon <[email protected]>

Author: amarziali

dd-java-agent/agent-otel/otel-shim/src/main/java/datadog/opentelemetry/shim/context/OtelContext.java

@@ -45,13 +45,13 @@ public Scope makeCurrent() {
   public <V> V get(ContextKey<V> key) {
     if (OTEL_CONTEXT_SPAN_KEY.equals(key.toString())) {
       AgentSpan span = AgentSpan.fromContext(delegate);
-      if (span != null) {
+      if (span != null && span.isValid()) {
         return (V) toOtelSpan(span);
       }
       // fall-through and check for non-datadog span data
     } else if (OTEL_CONTEXT_ROOT_SPAN_KEY.equals(key.toString())) {
       AgentSpan span = AgentSpan.fromContext(delegate);
-      if (span != null) {
+      if (span != null && span.isValid()) {
         return (V) toOtelSpan(span.getLocalRootSpan());
       }
       // fall-through and check for non-datadog span data

dd-java-agent/instrumentation/opentelemetry/opentelemetry-1.4/src/test/groovy/opentelemetry14/context/ContextTest.groovy

@@ -32,25 +32,33 @@ class ContextTest extends InstrumentationSpecification {
 
     when:
     def currentSpan = Span.current()
+    def currentSpanFromContext = Span.fromContext(Context.current())
+    def currentSpanFromContextOrNull = Span.fromContextOrNull(Context.current())
 
-    then:
+    then: "current span must be invalid or null"
     currentSpan != null
-    currentSpan.spanContext.traceId == "00000000000000000000000000000000"
-    currentSpan.spanContext.spanId == "0000000000000000"
+    !currentSpan.spanContext.valid
+    currentSpanFromContext != null
+    !currentSpanFromContext.spanContext.valid
+    currentSpanFromContextOrNull == null
 
     when:
     def scope = otelSpan.makeCurrent()
     currentSpan = Span.current()
+    currentSpanFromContext = Span.fromContext(Context.current())
+    currentSpanFromContextOrNull = Span.fromContextOrNull(Context.current())
 
-    then:
+    then: "OTel span must be current span"
     currentSpan == otelSpan
+    currentSpanFromContext == otelSpan
+    currentSpanFromContextOrNull == otelSpan
 
     when:
     def ddSpan = TEST_TRACER.startSpan("dd-api", "other-name")
     def ddScope = TEST_TRACER.activateManualSpan(ddSpan)
     currentSpan = Span.current()
 
-    then:
+    then: "Datadog span must be current span"
     currentSpan.spanContext.traceId == ddSpan.traceId.toHexString()
     currentSpan.spanContext.spanId == DDSpanId.toHexStringPadded(ddSpan.spanId)
 

dd-java-agent/instrumentation/opentelemetry/opentelemetry-1.4/src/test/groovy/opentelemetry14/context/propagation/MissingTraceContextPropagatorTest.groovy

@@ -0,0 +1,38 @@
+package opentelemetry14.context.propagation
+
+import datadog.trace.agent.test.InstrumentationSpecification
+import io.opentelemetry.api.GlobalOpenTelemetry
+import io.opentelemetry.api.trace.Span
+import io.opentelemetry.api.trace.propagation.W3CTraceContextPropagator
+import io.opentelemetry.context.propagation.TextMapPropagator
+
+import static io.opentelemetry.context.Context.root
+
+class MissingTraceContextPropagatorTest extends InstrumentationSpecification {
+  @Override
+  void configurePreAgent() {
+    super.configurePreAgent()
+
+    injectSysConfig("dd.integration.opentelemetry.experimental.enabled", "true")
+  }
+
+  def "extract on missing tracecontext should return an empty context"(TextMapPropagator propagator) {
+    setup:
+    def headers = ["User-Agent":"test"]
+
+    when:
+    def context = propagator.extract(root(), headers, TextMap.INSTANCE)
+    def extractedSpan = Span.fromContext(context)
+
+    then: "Should not have a valid tracing context"
+    extractedSpan != null
+    !extractedSpan.spanContext.valid
+    Span.fromContextOrNull(context) == null
+
+    where:
+    propagator << [
+      GlobalOpenTelemetry.get().getPropagators().getTextMapPropagator(),
+      W3CTraceContextPropagator.getInstance()
+    ]
+  }
+}