PSF-BotServer/pslogin/src/main/scala/MDCPropagatingExecutionContext.scala

// Copyright (c) 2017 PSForever
// Taken from http://code.hootsuite.com/logging-contextual-info-in-an-asynchronous-scala-application/

import org.slf4j.MDC

import scala.concurrent.ExecutionContext

trait MDCPropagatingExecutionContext extends ExecutionContext {
  // name the self-type "self" so we can refer to it inside the nested class
  self =>

  override def prepare(): ExecutionContext = new ExecutionContext {
    // Save the call-site MDC state
    val context = MDC.getCopyOfContextMap

    def execute(r: Runnable): Unit = self.execute(new Runnable {
      def run(): Unit = {
        // Save the existing execution-site MDC state
        val oldContext = MDC.getCopyOfContextMap
        try {
          // Set the call-site MDC state into the execution-site MDC
          if (context != null )
            MDC.setContextMap(context)
          else
            MDC.clear()

          r.run()
        } finally {
          // Restore the existing execution-site MDC state
          if (oldContext != null)
            MDC.setContextMap(oldContext)
          else
            MDC.clear()
        }
      }
    })

    def reportFailure(t: Throwable): Unit = self.reportFailure(t)
  }
}

object MDCPropagatingExecutionContext {
  object Implicits {
    // Convenience wrapper around the Scala global ExecutionContext so you can just do:
    // import MDCPropagatingExecutionContext.Implicits.global
    implicit lazy val global = MDCPropagatingExecutionContextWrapper(ExecutionContext.Implicits.global)
  }
}

/**
  * Wrapper around an existing ExecutionContext that makes it propagate MDC information.
  */
class MDCPropagatingExecutionContextWrapper(wrapped: ExecutionContext)
  extends ExecutionContext with MDCPropagatingExecutionContext {

  override def execute(r: Runnable): Unit = wrapped.execute(r)

  override def reportFailure(t: Throwable): Unit = wrapped.reportFailure(t)
}

object MDCPropagatingExecutionContextWrapper {
  def apply(wrapped: ExecutionContext): MDCPropagatingExecutionContextWrapper = {
    new MDCPropagatingExecutionContextWrapper(wrapped)
  }
}