1 files changed, 70 insertions, 0 deletions
diff --git a/kamon-core/src/main/scala/kamon/trace/ActiveSpan.scala b/kamon-core/src/main/scala/kamon/trace/ActiveSpan.scala
new file mode 100644
index 00000000..3a46d94f
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/trace/ActiveSpan.scala
@@ -0,0 +1,70 @@
+package kamon.trace
+
+/**
+  * Wraps a [[kamon.trace.Span]] that has been activated in the current Thread. By activated we really mean, it is
+  * stored in a ThreadLocal value inside the tracer until [[kamon.trace.ActiveSpan#deactivate()]] is called.
+  *
+  * When a [[kamon.trace.Span]] is activated it will keep a reference to the previously active Span on the current
+  * Thread, take it's place as the currently active Span and put the original one once this ActiveSpan gets deactivated.
+  *
+  */
+trait ActiveSpan extends Span {
+
+  /**
+    * Sets the currently active Span to whatever Span was active when this Span was activated.
+    *
+    */
+  def deactivate(): Unit
+}
+
+object ActiveSpan {
+
+  final class Default(wrappedSpan: Span, restoreOnDeactivate: ActiveSpan, tl: ThreadLocal[ActiveSpan])
+      extends ActiveSpan {
+
+    override def deactivate(): Unit =
+      tl.set(restoreOnDeactivate)
+
+    //
+    //  Forward all other members to the wrapped Span.
+    //
+
+    override def annotate(annotation: Span.Annotation): Span =
+      wrappedSpan.annotate(annotation)
+
+    override def addSpanTag(key: String, value: String): Span =
+      wrappedSpan.addSpanTag(key, value)
+
+    override def addMetricTag(key: String, value: String): Span =
+      wrappedSpan.addMetricTag(key, value)
+
+    override def addBaggage(key: String, value: String): Span =
+      wrappedSpan.addBaggage(key, value)
+
+    override def getBaggage(key: String): Option[String] =
+      wrappedSpan.getBaggage(key)
+
+    override def disableMetricsCollection(): Span =
+      wrappedSpan.disableMetricsCollection()
+
+    override def context(): SpanContext =
+      wrappedSpan.context()
+
+    override def setOperationName(operationName: String): Span =
+      wrappedSpan.setOperationName(operationName)
+
+    override def finish(): Unit =
+      wrappedSpan.finish()
+
+    override def finish(finishMicros: Long): Unit =
+      wrappedSpan.finish(finishMicros)
+
+    override def capture(): Continuation =
+      wrappedSpan.capture()
+  }
+
+  object Default {
+    def apply(wrappedSpan: Span, restoreOnDeactivate: ActiveSpan, tl: ThreadLocal[ActiveSpan]): Default =
+      new Default(wrappedSpan, restoreOnDeactivate, tl)
+  }
+}
+\ No newline at end of file