gistfile1.scala

class MDCExecutionContextExecutor(val context: java.util.Map[_, _], val delegate: ExecutionContext) extends ExecutionContextExecutor {
  def execute(runnable: Runnable) {
    delegate.execute(new Runnable {
      def run() {
        val oldContext = MDC.getCopyOfContextMap
        setContextMap(context)
        try {
          runnable.run()
        } finally {
          setContextMap(oldContext)
        }
      }
    })
  }

  private[this] def setContextMap(context: java.util.Map[_, _]) {
    if (context == null) {
      MDC.clear()
    } else {
      MDC.setContextMap(context)
    }
  }

  def reportFailure(t: Throwable) = delegate.reportFailure(t)
}

class MDCExecutionContext(wrapping: ExecutionContext) extends ExecutionContext {
  def execute(runnable: Runnable) = wrapping.execute(runnable)
  def reportFailure(failure: Throwable) = wrapping.reportFailure(failure)
  override def prepare =
    new MDCExecutionContextExecutor(MDC.getCopyOfContextMap, wrapping)
}

object CustomExecutionContext {

  object Implicits {
    implicit lazy val defaultContext: scala.concurrent.ExecutionContext = new MDCExecutionContext(play.api.libs.concurrent.Execution.defaultContext)
  }

  val defaultContext = Implicits.defaultContext
}