Akka Workshop Cheat Sheet

Contents

• Akka Cheat Sheet
• Robot Cheat Sheet
• Scala Cheat Sheet (List handling)

Akka Cheat Sheet

Creating an actor system (usually one per machine)

val system = ActorSystem("cluster")

 

Defining an actor:

class MyActor(myArg1: String) extends Actor {

   // initial actions here
   ...

   def receive = {
      case x: Robot => ...
   }

}

 

Creating an instance of an actor with one constructor argument:

val myActorRef =
    system.actorOf(Props(classOf[MyActor], "arg1"), "main")

 

Sending a message to an actor (ActorRef):

myActorRef ! "string message"

 

Configure your cluster node (use ipconfig/ifconfig to get your LAN ip address)
in src/main/resources/application.conf:

akka {
  ...
  remote {
    netty.tcp {
      hostname = "X.X.X.X" # your LAN ip address
  ...

  # add your own host and some other nodes to the initial cluster
  cluster {
    seed-nodes = [
      "akka.tcp://cluster@X.X.X.X:110", 
      "akka.tcp://cluster@Z.Z.Z.Z:110"]
  ...

}

 

Creating a broadcast router actor:

val broadcastRouter = system.actorOf(Props.empty.withRouter(
      ClusterRouterConfig(
        BroadcastRouter(),
        ClusterRouterSettings(totalInstances = 100, routeesPath = "/user/main", allowLocalRoutees = true, useRole = None))),
      name = "router")

 

How to let an actor do something every 10 seconds:

import scala.concurrent.duration.FiniteDuration
import java.util.concurrent.TimeUnit
import scala.concurrent.ExecutionContext.Implicits._

context.system.scheduler.schedule(FiniteDuration(10, TimeUnit.SECONDS), FiniteDuration(10, TimeUnit.SECONDS)) {
    self ! "every 10 seconds" // send message to myself every 10 seconds
}

 

Robot Cheat Sheet

Creating a random robot code

val robotCode = RobotCode.createRandomCode("your name here")

 

Creating a robot from a robot code

val robot = robotCode.evaluate

 

Performance optimization: Evaluating a list of robot codes using multiple cores:

import scala.concurrent.ExecutionContext.Implicits._

val myRobots = myRobotCodes.par.map(_.evaluate)

 

Print some debug info about a collection of robots

robot.DebugHelper.print(candidates: Seq[Robot])

 

Scala Cheat Sheet (List handling)

Concatenate two lists

val both = list1 ++ list2

 

Shuffling a list

import scala.util.Random
val shuffled = Random.shuffle(List(1, 2, 3))

 

Get a random number between 0 and 100 (not including 100):

Random.nextInt(100)

 

Sorting a list of objects by a numeric property

val sorted = myList.sortBy(_.myProperty)

 

Take first 100 elements of a list

val part = list.take(100)

 

Take everything except first 100 elements of a list

val part = list.drop(100)