Akka/Scala example source code file (LoggingDocSpec.scala)

This example Akka source code file (LoggingDocSpec.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, akka, anyref, loggingdocspec, map, mdc, myactor, mytype, received, req, starting, test, testing, testkit

The LoggingDocSpec.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package docs.event

import akka.testkit.AkkaSpec
import akka.actor.Actor
import akka.actor.Props

object LoggingDocSpec {

  //#my-actor
  import akka.event.Logging

  class MyActor extends Actor {
    val log = Logging(context.system, this)
    override def preStart() = {
      log.debug("Starting")
    }
    override def preRestart(reason: Throwable, message: Option[Any]) {
      log.error(reason, "Restarting due to [{}] when processing [{}]",
        reason.getMessage, message.getOrElse(""))
    }
    def receive = {
      case "test" => log.info("Received test")
      case x      => log.warning("Received unknown message: {}", x)
    }
  }
  //#my-actor

  import akka.event.Logging

  class MdcActor extends Actor {
    val log = Logging(this)
    def receive = {

      case _ => {
        //#mdc
        val mdc = Map("requestId" -> 1234, "visitorId" -> 5678)
        log.mdc(mdc)

        // Log something
        log.info("Starting new request")

        log.clearMDC()
        //#mdc
      }
    }
  }

  //#mdc-actor
  import Logging.MDC

  final case class Req(work: String, visitorId: Int)

  class MdcActorMixin extends Actor with akka.actor.DiagnosticActorLogging {
    var reqId = 0

    override def mdc(currentMessage: Any): MDC = {
      reqId += 1
      val always = Map("requestId" -> reqId)
      val perMessage = currentMessage match {
        case r: Req => Map("visitorId" -> r.visitorId)
        case _      => Map()
      }
      always ++ perMessage
    }

    def receive: Receive = {
      case r: Req => {
        log.info(s"Starting new request: ${r.work}")
      }
    }
  }

  //#mdc-actor

  //#my-event-listener
  import akka.event.Logging.InitializeLogger
  import akka.event.Logging.LoggerInitialized
  import akka.event.Logging.Error
  import akka.event.Logging.Warning
  import akka.event.Logging.Info
  import akka.event.Logging.Debug

  class MyEventListener extends Actor {
    def receive = {
      case InitializeLogger(_)                        => sender() ! LoggerInitialized
      case Error(cause, logSource, logClass, message) => // ...
      case Warning(logSource, logClass, message)      => // ...
      case Info(logSource, logClass, message)         => // ...
      case Debug(logSource, logClass, message)        => // ...
    }
  }
  //#my-event-listener

  //#my-source
  import akka.event.LogSource
  import akka.actor.ActorSystem

  object MyType {
    implicit val logSource: LogSource[AnyRef] = new LogSource[AnyRef] {
      def genString(o: AnyRef): String = o.getClass.getName
      override def getClazz(o: AnyRef): Class[_] = o.getClass
    }
  }

  class MyType(system: ActorSystem) {
    import MyType._
    import akka.event.Logging

    val log = Logging(system, this)
  }
  //#my-source
}

class LoggingDocSpec extends AkkaSpec {

  import LoggingDocSpec.{ MyActor, MdcActor, MdcActorMixin, Req }

  "use a logging actor" in {
    val myActor = system.actorOf(Props[MyActor])
    myActor ! "test"
  }

  "use a MDC logging actor" in {
    val mdcActor = system.actorOf(Props[MdcActor])
    mdcActor ! "some request"
  }

  "use a MDC logging actor by mixin" in {
    val mdcActor = system.actorOf(Props[MdcActorMixin])
    mdcActor ! Req("some request", 5678)
  }

  "allow registration to dead letters" in {
    new AnyRef {
      //#deadletters
      import akka.actor.{ Actor, DeadLetter, Props }

      class Listener extends Actor {
        def receive = {
          case d: DeadLetter => println(d)
        }
      }
      val listener = system.actorOf(Props(classOf[Listener], this))
      system.eventStream.subscribe(listener, classOf[DeadLetter])
      //#deadletters
    }
  }

  "demonstrate logging more arguments" in {
    //#array
    val args = Array("The", "brown", "fox", "jumps", 42)
    system.log.debug("five parameters: {}, {}, {}, {}, {}", args)
    //#array
  }

}