The following experiment registers for termination of the internal actor
used by the ask pattern.
The Termination message is received when the route completes normally or
times out. Closing the connection from the client has no impact on the
internal actor, which survives until the timeout finally expires.
This is sufficient to avoid a leak of the resources used by the internal
actor.
However, it means that the actor (Tracker) that is actually responding to
the HTML request is unaware that the response cannot be delivered. That is
unfortunate for use cases with expensive response processing and lengthy
timeouts to cover the worst case.
import java.util.concurrent.TimeUnit
import akka.actor.{Actor, Props, Terminated}
import akka.http.scaladsl.server.Directives._
import akka.http.scaladsl.server.Route
import akka.util.Timeout
object DeathWatcher extends App {
import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.model._
import akka.stream.ActorMaterializer
implicit val system = ActorSystem()
implicit val materializer = ActorMaterializer()
implicit val executionContext = system.dispatcher
class Tracker extends Actor {
override def receive: Receive = {
case Terminated(c) =>
println("terminated", c)
case _: String =>
context.watch(sender)
}
}
val tracker = system.actorOf(Props[Tracker])
import akka.pattern.ask
implicit val timeout = Timeout(5, TimeUnit.SECONDS)
val route: Route =
path("success") {
onComplete(tracker ? "xxx") { r =>
complete(StatusCodes.OK)
}
}
Http().bindAndHandle(route, "localhost", 8080)
}
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