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

This example Akka source code file (FactorialBackend.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, actorlogging, actorsystem, akka, array, bigint, cluster, clustersystem, concurrent, factorial, factorialbackend, future, int, pattern, unit

The FactorialBackend.scala Akka example source code

package sample.cluster.factorial

import scala.annotation.tailrec
import scala.concurrent.Future
import com.typesafe.config.ConfigFactory
import akka.actor.Actor
import akka.actor.ActorLogging
import akka.actor.ActorSystem
import akka.actor.Props
import akka.pattern.pipe

//#backend
class FactorialBackend extends Actor with ActorLogging {

  import context.dispatcher

  def receive = {
    case (n: Int) =>
      Future(factorial(n)) map { result => (n, result) } pipeTo sender()
  }

  def factorial(n: Int): BigInt = {
    @tailrec def factorialAcc(acc: BigInt, n: Int): BigInt = {
      if (n <= 1) acc
      else factorialAcc(acc * n, n - 1)
    }
    factorialAcc(BigInt(1), n)
  }

}
//#backend

object FactorialBackend {
  def main(args: Array[String]): Unit = {
    // Override the configuration of the port when specified as program argument
    val port = if (args.isEmpty) "0" else args(0)
    val config = ConfigFactory.parseString(s"akka.remote.netty.tcp.port=$port").
      withFallback(ConfigFactory.parseString("akka.cluster.roles = [backend]")).
      withFallback(ConfigFactory.load("factorial"))

    val system = ActorSystem("ClusterSystem", config)
    system.actorOf(Props[FactorialBackend], name = "factorialBackend")

    system.actorOf(Props[MetricsListener], name = "metricsListener")
  }
}