How do I make 10 http requests simultaneously?

I have 10 requests

  val reqTemplate = quickRequest.post(uri"http://localhost:8280/delay/1")
  val requests = for {i <- 1 to 10} yield {
    reqTemplate.body(s"{test:$i}")
  }

How do I send these requests simultaneously?

I tried


  val responseTasks = reqs.map(SttpClient.send)
  val allResponsesTask: Task[List[Response[String]]] = ZIO.collectAllPar(responseTasks)

  val appLogic: Task[Unit] = for {
    resps <- allResponsesTask
    resp <- resps
    _ <- putStrLn(resp.toString())
    _ <- putStrLn("Done")
  } yield ()

  Runtime.default.unsafeRunAsync(appLogic)

But that is giving me all sorts of fun compile errors.

Error:(18, 74) type mismatch;
 found   : scala.collection.immutable.IndexedSeq[zio.ZIO[sttp.client.asynchttpclient.zio.SttpClient,Throwable,sttp.client.Response[String]]]
    (which expands to)  scala.collection.immutable.IndexedSeq[zio.ZIO[zio.Has[sttp.client.SttpBackend[zio.Task,Nothing,sttp.client.asynchttpclient.WebSocketHandler]],Throwable,sttp.client.Response[String]]]
 required: Iterable[zio.ZIO[Any,Throwable,sttp.client.Response[String]]]
  val allResponsesTask: Task[List[Response[String]]] = ZIO.collectAllPar(responseTasks)
Error:(23, 7) type mismatch;
 found   : zio.ZIO[zio.console.Console,Nothing,Unit]
    (which expands to)  zio.ZIO[zio.Has[zio.console.Console.Service],Nothing,Unit]
 required: scala.collection.GenTraversableOnce[?]
    _ <- putStrLn(response.toString())
Error:(22, 14) type mismatch;
 found   : List[Nothing]
 required: zio.ZIO[Any,Throwable,Unit]
    response <- responses

Solution

The problem is that you have declared the an Sttp dependency but you haven't provided it.

If you annotate the responsesTask you'll see it is actually of type Seq[ZIO[SttpClient, Throwable, Response[String]]] meaning that you need to provide a client in order to satisfy the dependency.

I would change it to something like:

  val allResponsesTask: Task[List[Response[String]]] = 
    ZIO.collectAllPar(responseTasks)
      .provideLayer(AsyncHttpClientZioBackend.layer())

Note that I added the layer here for simplicity sake, but generally you want to add all layers at the edge of your application, since creating a layer is not free.