Ensure Propagators are still run when DD_TRACE_PROPAGATION_BEHAVIOR_EXTRACT=ignore (#8604)

* saving changes

* cleanup and adding tests

* addressing PR comments

* optimizing calls to config

Author: mhlidd

dd-trace-core/src/main/java/datadog/trace/core/CoreTracer.java

@@ -1514,28 +1514,31 @@ private DDSpanContext buildSpanContext() {
       String parentServiceName = null;
       boolean isRemote = false;
 
-      if (parentContext != null
-          && parentContext.isRemote()
-          && Config.get().getTracePropagationBehaviorExtract()
-              == TracePropagationBehaviorExtract.RESTART) {
-        SpanLink link;
-        if (parentContext instanceof ExtractedContext) {
-          ExtractedContext pc = (ExtractedContext) parentContext;
-          link =
-              DDSpanLink.from(
-                  pc,
-                  SpanAttributes.builder()
-                      .put("reason", "propagation_behavior_extract")
-                      .put("context_headers", pc.getPropagationStyle().toString())
-                      .build());
-        } else {
-          link = SpanLink.from(parentContext);
+      TracePropagationBehaviorExtract behaviorExtract =
+          Config.get().getTracePropagationBehaviorExtract();
+      if (parentContext != null && parentContext.isRemote()) {
+        if (behaviorExtract == TracePropagationBehaviorExtract.IGNORE) {
+          // reset links that may have come terminated span links
+          links = new ArrayList<>();
+          parentContext = null;
+        } else if (behaviorExtract == TracePropagationBehaviorExtract.RESTART) {
+          links = new ArrayList<>();
+          SpanLink link =
+              (parentContext instanceof ExtractedContext)
+                  ? DDSpanLink.from(
+                      (ExtractedContext) parentContext,
+                      SpanAttributes.builder()
+                          .put("reason", "propagation_behavior_extract")
+                          .put(
+                              "context_headers",
+                              ((ExtractedContext) parentContext).getPropagationStyle().toString())
+                          .build())
+                  : SpanLink.from(parentContext);
+          links.add(link);
+          parentContext = null;
         }
-        // reset links that may have come terminated span links
-        links = new ArrayList<>();
-        links.add(link);
-        parentContext = null;
       }
+
       // Propagate internal trace.
       // Note: if we are not in the context of distributed tracing and we are starting the first
       // root span, parentContext will be null at this point.

dd-trace-core/src/test/groovy/datadog/trace/core/CoreSpanBuilderTest.groovy

@@ -363,6 +363,22 @@ class CoreSpanBuilderTest extends DDCoreSpecification {
     link.traceState() == extractedContext.propagationTags.headerValue(PropagationTags.HeaderType.W3C)
   }
 
+  def "build context from ExtractedContext with TRACE_PROPAGATION_BEHAVIOR_EXTRACT=ignore"() {
+    setup:
+    injectSysConfig("trace.propagation.behavior.extract", "ignore")
+    def extractedContext = new ExtractedContext(DDTraceId.ONE, 2, PrioritySampling.SAMPLER_DROP, null, 0, [:], [:], null, PropagationTags.factory().fromHeaderValue(PropagationTags.HeaderType.DATADOG, "_dd.p.dm=934086a686-4,_dd.p.anytag=value"), null, DATADOG)
+    final DDSpan span = tracer.buildSpan("test", "op name")
+      .asChildOf(extractedContext).start()
+
+    expect:
+    span.traceId != extractedContext.traceId
+    span.parentId != extractedContext.spanId
+    span.samplingPriority() == PrioritySampling.UNSET
+
+
+    assert span.links.size() == 0
+  }
+
   def "TagContext should populate default span details"() {
     setup:
     def thread = Thread.currentThread()

internal-api/src/main/java/datadog/trace/api/Config.java

@@ -1042,14 +1042,8 @@ private Config(final ConfigProvider configProvider, final InstrumenterConfig ins
       }
       // Now we can check if we should pick the default injection/extraction
 
-      if (extract.isEmpty()) {
-        extract = DEFAULT_TRACE_PROPAGATION_STYLE;
-      }
-
       tracePropagationStylesToExtract =
-          tracePropagationBehaviorExtract == TracePropagationBehaviorExtract.IGNORE
-              ? new HashSet<>()
-              : extract;
+          extract.isEmpty() ? DEFAULT_TRACE_PROPAGATION_STYLE : extract;
 
       tracePropagationStylesToInject = inject.isEmpty() ? DEFAULT_TRACE_PROPAGATION_STYLE : inject;
 

internal-api/src/test/groovy/datadog/trace/api/ConfigTest.groovy

@@ -2679,20 +2679,6 @@ class ConfigTest extends DDSpecification {
     config.finalDebuggerSymDBUrl == "http://localhost:8126/symdb/v1/input"
   }
 
-  def "specify overrides for PROPAGATION_STYLE_EXTRACT when TRACE_PROPAGATION_BEHAVIOR_EXTRACT=ignore"() {
-    setup:
-    def prop = new Properties()
-    prop.setProperty(PROPAGATION_STYLE_EXTRACT, "Datadog, B3")
-    prop.setProperty(TRACE_PROPAGATION_BEHAVIOR_EXTRACT, "ignore")
-
-    when:
-    Config config = Config.get(prop)
-
-    then:
-    config.tracePropagationBehaviorExtract == TracePropagationBehaviorExtract.IGNORE
-    config.tracePropagationStylesToExtract.toList() == []
-  }
-
   def "verify try/catch behavior for invalid strings for TRACE_PROPAGATION_BEHAVIOR_EXTRACT"() {
     setup:
     def prop = new Properties()