akka-stream

I am writing a pure websocket web application, meaning that prior to the websocket upgrade there is no user/client step, more specifically: Authentication request goes over websockets as does the rest of the communication There is/are: Exactly ONE websocket endpoint on /api/ws Multiple clients connected to that endpoint Multiple projects for multiple clients Now, not each client has access to each project - the access control for that is implemented on the server side (ofc) and has nothing to do with websockets per se. My problem is, that I want to allow collaboration, meaning that N clients

I'm trying to implement an Akka Streams Flow that will convert a stream of JSON objects to a stream of a single array of JSON objects. I can use Concat to add an "[" before and "]" after, as well as Zip to insert commas in between elements, but I can't figure out how to not insert the final comma. The code I have so far is: trait JsonStreamSupport { protected def toJsonArrayString[T : Writes] = Flow[T].map(Json.toJson(_)).map(_.toString()).via(jsonArrayWrapper) private[this] val jsonArrayWrapper: Flow[String, String, NotUsed] = Flow.fromGraph(GraphDSL.create() { implicit b => import GraphDSL

Is there an idiomatic way of handling Akka stream's Source first element in a special way? What I have now is: var firstHandled = false source.map { elem => if(!firstHandled) { //handle specially firstHandled = true } else { //handle normally } } Thanks While I would generally go with Ramon's answer, you could also use prefixAndTail , with a prefix of 1, together with flatMapConcat to achieve something similar: val src = Source(List(1, 2, 3, 4, 5)) val fst = Flow[Int].map(i => s"First: $i") val rst = Flow[Int].map(i => s"Rest: $i") val together = src.prefixAndTail(1).flatMapConcat { case (head

I'm trying to make sense of the error(s) I'm seeing below, and to learn how to fix it. could not find implicit value for parameter materializer: akka.Stream.Materializer val fut: Future[Result] = action.apply(fakeRequest).run ^ not enough arguments for method run (implicit materializer: akka.stream.Materializer)scala.concurrent.Future[play.api.mvc.Result]. Unspecified value parameter materializer. val fut: Future[Result] = action.apply(fakeRequest).run ^ Here is the test code that produced the error(s): package com.foo.test import com.foo.{Api, BoundingBox} import org.scalatest.{FlatSpec,

I have an Akka Stream application with a single flow/graph. I want to measure the flow rate at the source and log it every 5 seconds, like 'received 3 messages in the last 5 seconds'. I tried with, someOtherFlow .groupedWithin(Integer.MAX_VALUE, 5 seconds) .runForeach(seq => log.debug(s"received ${seq.length} messages in the last 5 seconds") ) but it only outputs when there are messages, no empty list when there are 0 messages. I want the 0's as well. Is this possible? You could try something like src .conflateWithSeed(_ ⇒ 1){ case (acc, _) ⇒ acc + 1 } .zip(Source.tick(5.seconds, 5.seconds,

I try to redirect/forward a TCP stream to another Sink with Akka 2.4.3. The program should open a server socket, listen for incoming connections and then consume the tcp stream. Our sender does not expect/accept replies from us so we never send back anything - we just consume the stream. After framing the tcp stream we need to transform the bytes into something more useful and send it to the Sink. I tried the following so far but i struggle especially with the part how to not sending tcp packets back to the sender and to properly connect the Sink. import scala.util.Failure import scala.util

Basically I want to allow a user to download a csv file from the server. Assume the CSV file already exists on the server. A API endpoint is exposed via GET /export. How do I stream the file from Akka HTTP server to client? This is what I have so far... Service: def export(): Future[IOResult] = { FileIO.fromPath(Paths.get("file.csv")) .to(Sink.ignore) .run() } Route: pathPrefix("export") { pathEndOrSingleSlash { get { complete(HttpEntity(ContentTypes.`text/csv`, export()) } } } The Akka-Stream API allow you to create an entity directly out of a Source[ByteString, _] , so you can do something

I'm trying to understand how to use the new akka.http library. I would like to send an http request to a server and read the whole response body as a single String in order to produce a Source[String,?] . Here is the best solution I was able to produce so far: def get( modelID: String, pool: Flow[(HttpRequest,Int),(Try[HttpResponse],Int),Http.HostConnectionPool] ): Source[String,Unit] = { val uri = reactionsURL(modelID) val req = HttpRequest(uri = uri) Source.single( (req,0) ) .via( pool ) .map { case (Success(resp),_) => resp.entity.dataBytes.map( _.decodeString("utf-8") ) }.flatten

I'm using Akka 2.4.4 and trying to move from Apache HttpAsyncClient (unsuccessfully). Below is simplified version of code that I use in my project. The problem is that it hangs if I send more than 1-3 requests to the flow. So far after 6 hours of debugging I couldn't even locate the problem. I don't see exceptions, error logs, events in Decider . NOTHING :) I tried reducing connection-timeout setting to 1s thinking that maybe it's waiting for response from the server but it didn't help. What am I doing wrong ? import akka.actor.ActorSystem import akka.http.scaladsl.Http import akka.http