1 files changed, 36 insertions, 0 deletions
diff --git a/kamon-examples/kamon-play-example/app/filters/TraceLocalFilter.scala b/kamon-examples/kamon-play-example/app/filters/TraceLocalFilter.scala
new file mode 100644
index 00000000..c9600fad
--- /dev/null
+++ b/kamon-examples/kamon-play-example/app/filters/TraceLocalFilter.scala
@@ -0,0 +1,36 @@
+package filters
+
+import kamon.trace.{TraceRecorder, TraceLocal}
+import play.api.Logger
+import play.api.mvc.{Result, RequestHeader, Filter}
+import play.api.libs.concurrent.Execution.Implicits.defaultContext
+import scala.concurrent.Future
+
+object TraceLocalKey extends TraceLocal.TraceLocalKey {
+  type ValueType = String
+}
+
+/*
+ By default Kamon spreads the trace-token-header-name but sometimes is necessary pass through the application requests with some infomation like
+ extra headers, with kamon it's possible using TraceLocalStorage, in Play applications we can do an Action Filter or using Action Composition,
+ in this example we are using a simple filter where given a Header store the value and then put the value in the result headers..
+
+ More detailed used of TraceLocalStorage: https://github.com/kamon-io/Kamon/blob/b17539d231da923ea854c01d2c69eb02ef1e85b1/kamon-core/src/test/scala/kamon/trace/TraceLocalSpec.scala
+ */
+object TraceLocalFilter extends Filter {
+  val logger = Logger(this.getClass)
+  val TraceLocalStorageKey = "MyTraceLocalStorageKey"
+
+  override def apply(next: (RequestHeader) ⇒ Future[Result])(header: RequestHeader): Future[Result] = {
+    TraceRecorder.withTraceContext(TraceRecorder.currentContext) {
+
+      TraceLocal.store(TraceLocalKey)(header.headers.get(TraceLocalStorageKey).getOrElse("unknown"))
+
+      next(header).map {
+        val traceTokenValue = TraceLocal.retrieve(TraceLocalKey).getOrElse("unknown")
+        logger.info(s"traceTokenValue: $traceTokenValue")
+        result ⇒ result.withHeaders((TraceLocalStorageKey -> traceTokenValue))
+      }
+    }
+  }
+}