+ core: refactor MDC facilities and closes #100

3 files changed, 61 insertions, 3 deletions

diff --git a/kamon-core/src/main/scala/kamon/instrumentation/akka/ActorLoggingInstrumentation.scala b/kamon-core/src/main/scala/kamon/instrumentation/akka/ActorLoggingInstrumentation.scala
index 6b90a81e..e0e5d316 100644
--- a/kamon-core/src/main/scala/kamon/instrumentation/akka/ActorLoggingInstrumentation.scala
+++ b/kamon-core/src/main/scala/kamon/instrumentation/akka/ActorLoggingInstrumentation.scala
@@ -16,12 +16,13 @@
 
 package akka.kamon.instrumentation
 
+import kamon.trace.logging.MdcKeysSupport
 import kamon.trace.{ TraceContextAware, TraceRecorder }
 import org.aspectj.lang.ProceedingJoinPoint
 import org.aspectj.lang.annotation._
 
 @Aspect
-class ActorLoggingInstrumentation {
+class ActorLoggingInstrumentation extends MdcKeysSupport {
 
   @DeclareMixin("akka.event.Logging.LogEvent+")
   def mixinTraceContextAwareToLogEvent: TraceContextAware = TraceContextAware.default
@@ -41,7 +42,9 @@ class ActorLoggingInstrumentation {
   @Around("withMdcInvocation(logSource, logEvent, logStatement)")
   def aroundWithMdcInvocation(pjp: ProceedingJoinPoint, logSource: String, logEvent: TraceContextAware, logStatement: () ⇒ _): Unit = {
     TraceRecorder.withInlineTraceContextReplacement(logEvent.traceContext) {
-      pjp.proceed()
+      withMdc {
+        pjp.proceed()
+      }
     }
   }
 }
diff --git a/kamon-core/src/main/scala/kamon/trace/TraceLocal.scala b/kamon-core/src/main/scala/kamon/trace/TraceLocal.scala
index 0766af74..a7296c31 100644
--- a/kamon-core/src/main/scala/kamon/trace/TraceLocal.scala
+++ b/kamon-core/src/main/scala/kamon/trace/TraceLocal.scala
@@ -16,14 +16,28 @@
 
 package kamon.trace
 
-import scala.collection.concurrent.TrieMap
 import kamon.trace.TraceLocal.TraceLocalKey
 
+import scala.collection.concurrent.TrieMap
+
 object TraceLocal {
+
   trait TraceLocalKey {
     type ValueType
   }
 
+  trait AvailableToMdc extends TraceLocalKey {
+    override type ValueType = String
+    def mdcKey: String
+  }
+
+  object AvailableToMdc {
+    case class DefaultKeyAvailableToMdc(mdcKey: String) extends AvailableToMdc
+
+    def fromKey(mdcKey: String): AvailableToMdc = DefaultKeyAvailableToMdc(mdcKey)
+    def apply(mdcKey: String): AvailableToMdc = fromKey(mdcKey)
+  }
+
   def store(key: TraceLocalKey)(value: key.ValueType): Unit = TraceRecorder.currentContext match {
     case ctx: DefaultTraceContext ⇒ ctx.traceLocalStorage.store(key)(value)
     case EmptyTraceContext        ⇒ // Can't store in the empty context.
@@ -33,6 +47,8 @@ object TraceLocal {
     case ctx: DefaultTraceContext ⇒ ctx.traceLocalStorage.retrieve(key)
     case EmptyTraceContext        ⇒ None // Can't retrieve anything from the empty context.
   }
+
+  def storeForMdc(key: String, value: String): Unit = store(AvailableToMdc.fromKey(key))(value)
 }
 
 class TraceLocalStorage {
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]
+  }
+}