watch

Watch a specific ActorRef and signal a failure downstream once the actor terminates.

Actor interop operators

Signature

Source.watchSource.watch Flow.watchFlow.watch

Description

Watch a specific ActorRef and signal a failure downstream once the actor terminates. The signaled failure will be an WatchedActorTerminatedException WatchedActorTerminatedException.

Example

An ActorRef can be can be watched and the stream will fail with WatchedActorTerminatedException when the actor terminates.

Scala

copysourceval ref: ActorRef = someActor()
val flow: Flow[String, String, NotUsed] =
  Flow[String].watch(ref).recover {
    case _: WatchedActorTerminatedException => s"$ref terminated"
  }

Java

copysourcefinal ActorRef ref = someActor();
Flow<String, String, NotUsed> flow =
    Flow.of(String.class)
        .watch(ref)
        .recover(akka.stream.WatchedActorTerminatedException.class, () -> ref + " terminated");

Reactive Streams semantics