Version: 2.0.x

Akka Interop

Akka Interop gives you the ability to send and receive messages between zio actors and akka typed actors.

To use Akka Interops you need in your build.sbt:

libraryDependencies += "dev.zio" %% "zio-actors-akka-interop" % "0.1.0"

Imports required for example:

import zio.actors.Actor.Stateful
import zio.actors.{ ActorSystem, ActorRef, Context, Supervisor }
import zio.actors.akka.{ AkkaTypedActor, AkkaTypedActorRefLocal }
import zio.{ ZIO, IO, Runtime }

import akka.actor.typed
import akka.actor.typed.Behavior
import akka.actor.typed.scaladsl.Behaviors
import akka.actor.typed.Scheduler
import akka.util.Timeout

import scala.concurrent.duration._

Case class for messages that zio actor send and receive from akka actor:

sealed trait TypedMessage[+_]
case class PingToZio(zioReplyToActor: ActorRef[ZioMessage], msg: String) extends TypedMessage[Unit]
case class PingFromZio(zioSenderActor: ActorRef[ZioMessage]) extends TypedMessage[Unit]

sealed trait ZioMessage[+_]
case class PongFromAkka(msg: String) extends ZioMessage[Unit]
case class Ping(akkaActor: AkkaTypedActorRefLocal[TypedMessage]) extends ZioMessage[Unit]

For zio actor basics, (Basics section). Here's the Stateful implementation for our zio actor:

val handler = new Stateful[Any, String, ZioMessage] {
  override def receive[A](state: String, msg: ZioMessage[A], context: Context): IO[Throwable, (String, A)] =
    msg match {             
      case PongFromAkka(msg) => ZIO.succeed((msg, ()))
      case Ping(akkaActor) =>
              for {
                 self <- context.self[ZioMessage]
                 _    <- akkaActor ! PingFromZio(self)
               } yield (state, ())
      case _=> ZIO.fail(new Exception("fail"))
    }
}

Akka actors (Creation akka actors), need a behavior, to define the messages to be handled, in this case send and receive messages to zio actor:

object TestBehavior {
    lazy val zioRuntime = Runtime.default
    def apply(): Behavior[TypedMessage[_]] =
      Behaviors.receiveMessage { message =>
        message match {                  
          case PingToZio(zioReplyToActor, msgToZio) => 
            zio.Unsafe.unsafe { implicit unsafe =>
              zioRuntime.unsafe.run(zioReplyToActor ! PongFromAkka(msgToZio))
            }
          case PingFromZio(zioSenderActor)          =>
            zio.Unsafe.unsafe { implicit unsafe => 
              zioRuntime.unsafe.run(zioSenderActor ! PongFromAkka("Pong from Akka"))
            }
        }
        Behaviors.same
      }
  } 

We are ready to start sending messages from zio to akka, or vice versa via fire-and-forget interaction pattern, but first we need to create a ZIO value with the created akka ActorRef(or ActorSystem), using AkkaTypedActor.make:

for {
  akkaSystem <- ZIO.succeed(typed.ActorSystem(TestBehavior(), "akkaSystem"))
  system     <- ActorSystem("zioSystem")
  akkaActor  <- AkkaTypedActor.make(akkaSystem)
  zioActor   <- system.make("zioActor", Supervisor.none, "", handler)
  _          <- akkaActor ! PingToZio(zioActor, "Ping from Akka")
  _          <- zioActor ! Ping(akkaActor)
} yield ()

There's also ask interaction pattern, that provides a way to send a message to an akka actor and expect a response. It's performed via ? method, and needs a parameter of type typed.ActorRef[R] => T (R represents the response type, T is the message type), with implicit values for akka.util.Timeout and akka.actor.typed.Scheduler:

sealed trait AskMessage[+_]
case class PingAsk(value: Int, replyTo: typed.ActorRef[Int]) extends AskMessage[Int]

object AskTestBehavior {
    def apply(): Behavior[AskMessage[_]] =
      Behaviors.receiveMessage { message =>
        message match {
          case PingAsk(value, replyTo) => replyTo ! (value * 2)
        }
        Behaviors.same
      }
  }

def PingAskDeferred(value: Int): typed.ActorRef[Int] => PingAsk 
       = (hiddenRef: typed.ActorRef[Int]) => PingAsk(value, hiddenRef)
       
import scala.concurrent.duration.DurationInt 
implicit val timeout: Timeout = 3.seconds
         
for {
  akkaAskSystem <- ZIO.succeed(typed.ActorSystem(AskTestBehavior(), "akkaSystem"))
  akkaActor <- AkkaTypedActor.make(akkaAskSystem)
  result    <- (akkaActor ? PingAskDeferred(1000)) (timeout, akkaAskSystem.scheduler)
} yield result == 2000

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