could not find implicit ...: akka.http.server.RoutingSetup

Question

While playing with, akka-http experimental 1.0-M2 I am trying to create a simple Hello world example.

import akka.actor.ActorSystem
import akka.http.Http
import akka.http.model.HttpResponse
import akka.http.server.Route
import akka.stream.FlowMaterializer
import akka.http.server.Directives._

object Server extends App {

  val host = "127.0.0.1"
  val port = "8080"

  implicit val system = ActorSystem("my-testing-system")
  implicit val fm = FlowMaterializer()

  val serverBinding = Http(system).bind(interface = host, port = port)
  serverBinding.connections.foreach { connection ⇒
    println("Accepted new connection from: " + connection.remoteAddress)
    connection handleWith Route.handlerFlow {
      path("") {
        get {
          complete(HttpResponse(entity = "Hello world?"))
        }
      }
    }
  }
}

Compilation fails with could not find implicit value for parameter setup: akka.http.server.RoutingSetup

Also, if I change

complete(HttpResponse(entity = "Hello world?"))

with

complete("Hello world?")

I get another error: type mismatch; found : String("Hello world?") required: akka.http.marshalling.ToResponseMarshallable

Answer 1

With research I was able to understand the issue to be lack of Execution Context. To solve both the issue I needed to include this:

implicit val executionContext = system.dispatcher

Looking into akka/http/marshalling/ToResponseMarshallable.scala I see ToResponseMarshallable.apply requires it which returns a Future[HttpResponse].

Also, in akka/http/server/RoutingSetup.scala, RoutingSetup.apply needs it.

May be akka team just needs to add some more @implicitNotFounds. I was able to find not exact but related answer at: direct use of Futures in Akka and spray Marshaller for futures not in implicit scope after upgrading to spray 1.2

Answer 2

Well found - this problem still exists with Akka HTTP 1.0-RC2, so the code for that now must look like this (given their API changes):

import akka.actor.ActorSystem
import akka.http.scaladsl.server._
import akka.http.scaladsl._
import akka.stream.ActorFlowMaterializer
import akka.stream.scaladsl.{Sink, Source}
import akka.http.scaladsl.model.HttpResponse
import Directives._
import scala.concurrent.Future

object BootWithRouting extends App {

  val host = "127.0.0.1"
  val port = 8080

  implicit val system = ActorSystem("my-testing-system")
  implicit val fm = ActorFlowMaterializer()
  implicit val executionContext = system.dispatcher

  val serverSource: Source[Http.IncomingConnection, Future[Http.ServerBinding]] =
    Http(system).bind(interface = host, port = port)

  serverSource.to(Sink.foreach {
    connection =>
      println("Accepted new connection from: " + connection.remoteAddress)
      connection handleWith Route.handlerFlow {
        path("") {
          get {
            complete(HttpResponse(entity = "Hello world?"))
          }
        }
      }
  }).run()
}