Trying to deserialize a serialized ActorRef without an ActorSystem in scope - Spark/Akka/Scala

Question

EDIT: Exception relating to serialising / deserialising Akka Actor remains after forEach is confirmed to be executing. I'm learning Akka and encountering this serialisation issue, I'm quite new to Akka and finding it quite difficult to figure out how best to approach a solution.

I have a class where the actorSystem and actor is created, that class calls a method in another class, I'd like to use my actor in that other class. So far I've tried:

Class a:
-create actor
-classB.methodX(actor)

Class b:
-methodX(actorRef)
--actorRef! message

currently the message from class b does not get sent whereas the class A ones do, this is making me think that I either need to instantiate a new Actor with the ActorRef that I'm passing in or, it's completely wrong.

I understand that the system needs to be present on all nodes but I'm unsure how to do that.

Edit: Code Snippets:

ClassA:
  private val system = ActorSystem("System")
  private val metricActor= system.actorOf(Props(new MetricActor("metrics")), name = "metrics")

metricActor ! message works fine

writeFiles(metricActor) //writeFiles is in another class


writeFiles(actor: ActorRef) {
  f.forEach(v => {
  actor ! message // this doesn't seem to work
})
}

Edited to provide more code.

full example of classB as it were

def writeFiles(bucket: String, filesToWrite: RDD[(String, String)], actor:ActorRef): Unit =
filesToWrite.foreachPartition(f => {
  f.foreach(v => {
    try {
      //actor  ! ProcessSingleItem(MetricItem("File Created"))
      logger.debug(s"Writing file:")
      writeFile()
    }
    catch {
      case e: Exception =>
        //actor ! ProcessSingleItem(CloudWatchMetricItem("File create failure")) 
        logger.error("Error creating file", e)
    }
  })
})

Akka actors are just small parts of a bigger machinery that is hidden away. The actor system is more like the car's engine and your actors can be said to be like accelerator etc. Do you think the accelerator alone is going to get you moving if the whole car is missing? — sarveshseri
@SarveshKumarSingh What might you suggest for solving my current dilemma? Should every node have a car? That seems extreme. Should a node have the capability of sending a message to the foot telling ti to press the accelerator? — null
The short answer -> Whatever node needs to behave like a car needs to have capabilities of a car. Just design your solution so that only car type nodes need to behave like cars. Other nodes can stay lightweight. — sarveshseri
@SarveshKumarSingh - Thanks for taking the time to comment, it doesn't really help though. — null
Yes. I certainly know it won't help much. Its just that actor can not function without an actor system. So you will just have to design with that in mind. — sarveshseri

slouc slouc · Accepted Answer · 2016-03-30T13:52:13

What you are describing should work. You didn't paste the full (but minimal!) code sample so I can't say what's the problem (maybe something in your foreach logic; we don'e even know what f is), but here's what definitely works. Try building up on that.

object Test extends App {

  class MetricActor extends Actor {
    def receive = {
      case a: String => println(a)
    }
  }

  private val system = ActorSystem("System")
  private val metricActor= system.actorOf(Props(new MetricActor()), name = "metrics")

  OtherClass.writeFiles(metricActor) // prints "foo"
}

// this is in other file:
object OtherClass {
  def writeFiles(actor: ActorRef) {
    actor ! "foo"
  }
}

EDIT: Turns out after discussion in comments that the problematic part was unrelated to Akka (try block was not even executing), but I will leave this here in case it helps someone.

Trying to deserialize a serialized ActorRef without an ActorSystem in scope - Spark/Akka/Scala

1 Answers