Merge pull request #988 from pnerg/w3c-parent-propagation

fix for w3c propagation of the proper parentSpanId (#986)

Author: SimunKaracic

core/kamon-core-tests/src/test/scala/kamon/trace/W3CTraceContextSpanPropagationSpec.scala

@@ -14,7 +14,7 @@ class W3CTraceContextSpanPropagationSpec extends WordSpecLike with Matchers with
       val headersMap = mutable.Map.empty[String, String]
       traceContextPropagation.write(testContext(), headerWriterFromMap(headersMap))
 
-      headersMap.get("traceparent").value shouldBe "00-00000000000000000000000001020304-0000000004030201-01"
+      headersMap.get("traceparent").value shouldBe "00-00000000000000000000000001020304-0000000002020202-01"
       headersMap.get("tracestate").value shouldBe ""
     }
 

core/kamon-core/src/main/scala/kamon/trace/SpanPropagation.scala

@@ -107,7 +107,7 @@ object W3CTraceContext {
 
     val samplingDecision = if (parent.trace.samplingDecision == SamplingDecision.Sample) "01" else "00"
 
-    s"$Version-${idToHex(parent.trace.id, 32)}-${idToHex(parent.id, 16)}-${samplingDecision}"
+    s"$Version-${idToHex(parent.trace.id, 32)}-${idToHex(parent.parentId, 16)}-${samplingDecision}"
   }
 }