1 files changed, 46 insertions, 0 deletions
diff --git a/kamon-core/src/main/scala/kamon/trace/ActiveSpanSource.scala b/kamon-core/src/main/scala/kamon/trace/ActiveSpanSource.scala
new file mode 100644
index 00000000..f4a363a6
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/trace/ActiveSpanSource.scala
@@ -0,0 +1,46 @@
+package kamon.trace
+
+
+trait Scope extends AutoCloseable {
+  def close(): Unit
+}
+
+trait ActiveSpanSource {
+  def activeSpan(): Span
+
+  def activate(span: Span): Scope
+  def activate(span: Span, finishOnClose: Boolean): Scope
+}
+
+object ActiveSpanSource {
+
+  final class ThreadLocalBased extends ActiveSpanSource {
+    private val emptySpan = Span.Empty(this)
+    private val storage: ThreadLocal[Span] = new ThreadLocal[Span] {
+      override def initialValue(): Span = emptySpan
+    }
+
+    override def activeSpan(): Span =
+      storage.get()
+
+    override def activate(span: Span): Scope =
+      activate(span, finishOnClose = false)
+
+    override def activate(span: Span, finishOnClose: Boolean): Scope = {
+      val previouslyActiveSpan = storage.get()
+      storage.set(span)
+
+      new Scope {
+        override def close(): Unit = {
+          storage.set(previouslyActiveSpan)
+          if (finishOnClose && span != null)
+            span.finish()
+        }
+      }
+    }
+  }
+
+  object ThreadLocalBased {
+    def apply(): ThreadLocalBased = new ThreadLocalBased()
+  }
+}
+\ No newline at end of file