retain propagated context for random trace-ids

Author: cleverchuk

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/SdkSpanBuilder.java

@@ -37,9 +37,13 @@
 /** {@link SdkSpanBuilder} is SDK implementation of {@link SpanBuilder}. */
 class SdkSpanBuilder implements SpanBuilder {
 
-  private static final Context ROOT_CONTEXT_WITH_RANDOM_TRACE_ID_BIT =
-      preparePrimordialContext(
-          TraceFlags.builder().setRandomTraceId(true).build(), TraceState.getDefault());
+  private static final Span RANDOM_TRACE_ID_PRIMORDIAL_SPAN =
+      Span.wrap(
+          SpanContext.create(
+              TraceId.getInvalid(),
+              SpanId.getInvalid(),
+              TraceFlags.builder().setRandomTraceId(true).build(),
+              TraceState.getDefault()));
 
   private final String spanName;
   private final InstrumentationScopeInfo instrumentationScopeInfo;
@@ -64,17 +68,6 @@ class SdkSpanBuilder implements SpanBuilder {
     this.spanLimits = spanLimits;
   }
 
-  /*
-   * A primordial context can be passed as the parent context for a root span
-   * if a non-default TraceFlags or TraceState need to be passed to the sampler
-   */
-  private static Context preparePrimordialContext(TraceFlags traceFlags, TraceState traceState) {
-    SpanContext spanContext =
-        SpanContext.create(TraceId.getInvalid(), SpanId.getInvalid(), traceFlags, traceState);
-    Span span = Span.wrap(spanContext);
-    return span.storeInContext(Context.root());
-  }
-
   @Override
   public SpanBuilder setParent(Context context) {
     if (context == null) {
@@ -198,7 +191,7 @@ public Span startSpan() {
       if (idGenerator.generatesRandomTraceIds()) {
         isTraceIdRandom = true;
         // Replace parentContext for sampling with one with RANDOM_TRACE_ID bit set
-        parentContextForSampler = ROOT_CONTEXT_WITH_RANDOM_TRACE_ID_BIT;
+        parentContextForSampler = parentContext.with(RANDOM_TRACE_ID_PRIMORDIAL_SPAN);
       } else {
         isTraceIdRandom = false;
       }