+ core: refactor MDC facilities and closes #100

1 files changed, 39 insertions, 0 deletions

diff --git a/kamon-core/src/main/scala/kamon/trace/logging/MdcKeysSupport.scala b/kamon-core/src/main/scala/kamon/trace/logging/MdcKeysSupport.scala
new file mode 100644
index 00000000..d79a3ab6
--- /dev/null
+++ b/kamon-core/src/main/scala/kamon/trace/logging/MdcKeysSupport.scala
@@ -0,0 +1,39 @@
+/*
+ * =========================================================================================
+ * Copyright © 2013-2014 the kamon project <http://kamon.io/>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
+ * except in compliance with the License. You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the
+ * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
+ * either express or implied. See the License for the specific language governing permissions
+ * and limitations under the License.
+ * =========================================================================================
+ */
+
+package kamon.trace.logging
+
+import kamon.trace.TraceLocal.AvailableToMdc
+import kamon.trace.{ EmptyTraceContext, DefaultTraceContext, TraceContext, TraceRecorder }
+
+import org.slf4j.MDC
+
+trait MdcKeysSupport {
+
+  def withMdc[A](thunk: ⇒ A): A = {
+    val keys = copyToMdc(TraceRecorder.currentContext)
+    try thunk finally keys.foreach(key ⇒ MDC.remove(key))
+  }
+
+  private[this] def copyToMdc(traceContext: TraceContext): Iterable[String] = traceContext match {
+    case ctx: DefaultTraceContext ⇒
+      ctx.traceLocalStorage.underlyingStorage.collect {
+        case (available: AvailableToMdc, value) ⇒ Map(available.mdcKey -> String.valueOf(value))
+      }.map { value ⇒ value.map { case (k, v) ⇒ MDC.put(k, v); k } }.flatten
+
+    case EmptyTraceContext ⇒ Iterable.empty[String]
+  }
+}