ActorSink.actorRefWithBackpressure

Sends the elements of the stream to the given ActorRef<T>ActorRef[T] of the new actors API with backpressure, to be able to signal demand when the actor is ready to receive more elements.

Actor interop operators

Dependency

The Akka dependencies are available from Akka’s library repository. To access them there, you need to configure the URL for this repository.

sbt

resolvers += "Akka library repository".at("https://repo.akka.io/maven")

Maven

<project>
  ...
  <repositories>
    <repository>
      <id>akka-repository</id>
      <name>Akka library repository</name>
      <url>https://repo.akka.io/maven</url>
    </repository>
  </repositories>
</project>

Gradle

repositories {
    mavenCentral()
    maven {
        url "https://repo.akka.io/maven"
    }
}

This operator is included in:

sbt

val AkkaVersion = "2.10.0+21-4d1074a3-SNAPSHOT"
libraryDependencies += "com.typesafe.akka" %% "akka-stream-typed" % AkkaVersion

Maven

<properties>
  <scala.binary.version>2.13</scala.binary.version>
</properties>
<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.typesafe.akka</groupId>
      <artifactId>akka-bom_${scala.binary.version}</artifactId>
      <version>2.10.0+21-4d1074a3-SNAPSHOT</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>
<dependencies>
  <dependency>
    <groupId>com.typesafe.akka</groupId>
    <artifactId>akka-stream-typed_${scala.binary.version}</artifactId>
  </dependency>
</dependencies>

Gradle

def versions = [
  ScalaBinary: "2.13"
]
dependencies {
  implementation platform("com.typesafe.akka:akka-bom_${versions.ScalaBinary}:2.10.0+21-4d1074a3-SNAPSHOT")

  implementation "com.typesafe.akka:akka-stream-typed_${versions.ScalaBinary}"
}

Signature

ActorSink.actorRefWithBackpressureActorSink.actorRefWithBackpressure

Description

Sends the elements of the stream to the given ActorRef<T>ActorRef[T] with backpressure, to be able to signal demand when the actor is ready to receive more elements. There is also a variant without a concrete acknowledge message accepting any message as such.

See also:

• ActorSink.actorRef Send elements to an actor of the new actors API, without considering backpressure
• Sink.actorRef Send elements to an actor of the classic actors API, without considering backpressure
• Sink.actorRefWithBackpressue The corresponding operator for the classic actors API

Examples

Scala

copysourceimport akka.actor.typed.ActorRef
import akka.stream.scaladsl.{ Sink, Source }
import akka.stream.typed.scaladsl.ActorSink

trait Ack
object Ack extends Ack

trait Protocol
case class Init(ackTo: ActorRef[Ack]) extends Protocol
case class Message(ackTo: ActorRef[Ack], msg: String) extends Protocol
case object Complete extends Protocol
case class Fail(ex: Throwable) extends Protocol

val actor: ActorRef[Protocol] = targetActor()

val sink: Sink[String, NotUsed] = ActorSink.actorRefWithBackpressure(
  ref = actor,
  messageAdapter = (responseActorRef: ActorRef[Ack], element) => Message(responseActorRef, element),
  onInitMessage = (responseActorRef: ActorRef[Ack]) => Init(responseActorRef),
  ackMessage = Ack,
  onCompleteMessage = Complete,
  onFailureMessage = (exception) => Fail(exception))

Source.single("msg1").runWith(sink)

Java

copysourceimport akka.NotUsed;
import akka.actor.typed.ActorRef;
import akka.actor.typed.ActorSystem;
import akka.stream.javadsl.Sink;
import akka.stream.javadsl.Source;
import akka.stream.typed.javadsl.ActorSink;


enum Ack {
  INSTANCE;
}

interface Protocol {}

class Init implements Protocol {
  private final ActorRef<Ack> ack;

  public Init(ActorRef<Ack> ack) {
    this.ack = ack;
  }
}

class Message implements Protocol {
  private final ActorRef<Ack> ackTo;
  private final String msg;

  public Message(ActorRef<Ack> ackTo, String msg) {
    this.ackTo = ackTo;
    this.msg = msg;
  }
}

class Complete implements Protocol {}

class Fail implements Protocol {
  private final Throwable ex;

  public Fail(Throwable ex) {
    this.ex = ex;
  }
}

  final ActorRef<Protocol> actorRef = // spawned actor

  final Complete completeMessage = new Complete();

  final Sink<String, NotUsed> sink =
      ActorSink.actorRefWithBackpressure(
          actorRef,
          (responseActorRef, element) -> new Message(responseActorRef, element),
          (responseActorRef) -> new Init(responseActorRef),
          Ack.INSTANCE,
          completeMessage,
          (exception) -> new Fail(exception));

  Source.single("msg1").runWith(sink, system);

Reactive Streams semantics