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Websocket fails with a Kleisli Routes monad

See original GitHub issue

Minimal example:

import scala.concurrent.duration._

import cats.implicits._
import cats.data.Kleisli
import cats.effect._
import fs2._
import org.http4s._
import org.http4s.dsl.Http4sDsl
import org.http4s.implicits._
import org.http4s.server.blaze._
import org.http4s.server.websocket.WebSocketBuilder
import org.http4s.websocket.WebSocketFrame

case class WebSocketRoutes[F[_]: Concurrent: Timer]() extends Http4sDsl[F] {

  val routes: HttpRoutes[F] = HttpRoutes.of[F] {
    case GET -> Root =>
      val toClient: Stream[F, WebSocketFrame] =
        Stream.awakeEvery[F](1.seconds).map(d => WebSocketFrame.Text(s"Ping! $d"))
      val fromClient: Pipe[F, WebSocketFrame, Unit] = _.evalMap {
        case WebSocketFrame.Text(t, _) => F.delay(println(t))
        case f                         => F.delay(println(s"Unknown type: $f"))
      }
      WebSocketBuilder[F].build(toClient, fromClient)
  }

}

object Middleware {

  def apply[F[_]: Sync](
      name: String
  )(httpApp: HttpApp[Kleisli[F, String, *]]): HttpApp[F] =
    Kleisli { request =>
      for {
        appRequest <- F.pure(request.mapK(Kleisli.liftK[F, String]))
        appResponse <- httpApp.run(appRequest).run(name)
        response = appResponse.mapK(Kleisli.applyK(name))
      } yield response
    }

}

object Main extends IOApp {

  type AppIO[A] = Kleisli[IO, String, A]

  def run(args: List[String]): IO[ExitCode] = {
    val routes = WebSocketRoutes[AppIO]().routes.orNotFound

    val app = Middleware("test")(routes)

    BlazeServerBuilder[IO](scala.concurrent.ExecutionContext.global)
      .bindHttp(8080, "localhost")
      .withHttpApp(app)
      .serve
      .compile
      .drain
      .as(ExitCode.Success)

  }

}

Full Stack trace:

[info] 23:11:17.950 [blaze-selector-1] INFO org.http4s.blaze.channel.nio1.NIO1SocketServerGroup - Accepted connection from /127.0.0.1:51343
[info] 23:11:17.974 [ioapp-compute-1] DEBUG org.http4s.server.blaze.Http1ServerStage$$anon$1 - Websocket key: Some(WebSocketContext(WebSocket(Stream(..),org.http4s.server.websocket.WebSocketBuilder$Builder$$Lambda$299/1538312351@2487cace,Kleisli(cats.data.KleisliFunctions$$Lambda$298/754950929@33f502e0)),Headers(),Kleisli(cats.data.KleisliFunctions$$Lambda$298/754950929@365d5f01)))
[info] Request headers: Headers(Host: 127.0.0.1:8080, Connection: Upgrade, Upgrade: websocket, Sec-WebSocket-Version: 13, Sec-WebSocket-Key: 4+mLlx5cT/kKSia8zG5MSw==)
[info] 23:11:17.985 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.Http1ServerStage$$anon$1 - Switching pipeline segments for websocket
[info] 23:11:17.999 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.Http1ServerStage$$anon$1 - Shutting down HttpPipeline
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.Http1ServerStage$$anon$1 - Canceled request
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.Http1ServerStage$$anon$1 - Shutting down.
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.blazecore.IdleTimeoutStage - Stage IdleTimeoutStage sending inbound command: Connected
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.WebSocketDecoder - Starting up.
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.WebSocketDecoder - Stage WebSocketDecoder sending inbound command: Connected
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.WSFrameAggregator - Starting up.
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.WSFrameAggregator - Stage WSFrameAggregator sending inbound command: Connected
[info] 23:11:18.000 [scala-execution-context-global-38] DEBUG org.http4s.blazecore.websocket.Http4sWSStage - Starting up.
[info] 23:11:18.006 [scala-execution-context-global-38] ERROR org.http4s.server.blaze.WSFrameAggregator - Exception caught when attempting inbound command
[info] java.lang.ClassCastException: cats.data.Kleisli cannot be cast to cats.effect.IO
[info]  at cats.effect.IOLowPriorityInstances$IOEffect.attempt(IO.scala:863)
[info]  at cats.syntax.ApplicativeErrorOps$.attempt$extension(applicativeError.scala:52)
[info]  at org.http4s.blazecore.websocket.Http4sWSStage.stageStartup(Http4sWSStage.scala:132)
[info]  at org.http4s.blaze.pipeline.Stage.inboundCommand(Stages.scala:75)
[info]  at org.http4s.blaze.pipeline.Stage.inboundCommand$(Stages.scala:73)
[info]  at org.http4s.blazecore.websocket.Http4sWSStage.inboundCommand(Http4sWSStage.scala:26)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand(Stages.scala:258)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand$(Stages.scala:254)
[info]  at org.http4s.server.blaze.WSFrameAggregator.sendInboundCommand(WSFrameAggregator.scala:22)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand(Stages.scala:276)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand$(Stages.scala:274)
[info]  at org.http4s.server.blaze.WSFrameAggregator.inboundCommand(WSFrameAggregator.scala:22)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand(Stages.scala:258)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand$(Stages.scala:254)
[info]  at org.http4s.server.blaze.WebSocketDecoder.sendInboundCommand(WebSocketDecoder.scala:14)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand(Stages.scala:276)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand$(Stages.scala:274)
[info]  at org.http4s.server.blaze.WebSocketDecoder.inboundCommand(WebSocketDecoder.scala:14)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand(Stages.scala:258)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand$(Stages.scala:254)
[info]  at org.http4s.blazecore.IdleTimeoutStage.sendInboundCommand(IdleTimeoutStage.scala:18)
[info]  at org.http4s.blaze.pipeline.Tail.replaceTail(Stages.scala:183)
[info]  at org.http4s.blaze.pipeline.Tail.replaceTail$(Stages.scala:162)
[info]  at org.http4s.server.blaze.Http1ServerStage.replaceTail(Http1ServerStage.scala:73)
[info]  at org.http4s.server.blaze.WebSocketSupport.$anonfun$renderResponse$7(WebSocketSupport.scala:83)
[info]  at scala.concurrent.impl.Promise$Transformation.run(Promise.scala:447)
[info]  at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
[info]  at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
[info]  at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
[info]  at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
[info]  at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
[info] 23:11:18.006 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.WSFrameAggregator - Shutting down.
[info] 23:11:18.006 [scala-execution-context-global-38] DEBUG org.http4s.server.blaze.WebSocketDecoder - Shutting down.
[info] 23:11:18.006 [scala-execution-context-global-38] DEBUG org.http4s.blazecore.IdleTimeoutStage - Shutting down idle timeout stage
[info] 23:11:18.006 [scala-execution-context-global-38] DEBUG org.http4s.blazecore.IdleTimeoutStage - Shutting down.
[info] 23:11:18.006 [scala-execution-context-global-38] DEBUG org.http4s.blaze.channel.nio1.NIO1HeadStage - Shutting down.
[info] 23:11:18.007 [blaze-selector-1] ERROR org.http4s.blaze.channel.nio1.NIO1HeadStage - Abnormal NIO1HeadStage termination
[info] java.lang.ClassCastException: cats.data.Kleisli cannot be cast to cats.effect.IO
[info]  at cats.effect.IOLowPriorityInstances$IOEffect.attempt(IO.scala:863)
[info]  at cats.syntax.ApplicativeErrorOps$.attempt$extension(applicativeError.scala:52)
[info]  at org.http4s.blazecore.websocket.Http4sWSStage.stageStartup(Http4sWSStage.scala:132)
[info]  at org.http4s.blaze.pipeline.Stage.inboundCommand(Stages.scala:75)
[info]  at org.http4s.blaze.pipeline.Stage.inboundCommand$(Stages.scala:73)
[info]  at org.http4s.blazecore.websocket.Http4sWSStage.inboundCommand(Http4sWSStage.scala:26)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand(Stages.scala:258)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand$(Stages.scala:254)
[info]  at org.http4s.server.blaze.WSFrameAggregator.sendInboundCommand(WSFrameAggregator.scala:22)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand(Stages.scala:276)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand$(Stages.scala:274)
[info]  at org.http4s.server.blaze.WSFrameAggregator.inboundCommand(WSFrameAggregator.scala:22)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand(Stages.scala:258)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand$(Stages.scala:254)
[info]  at org.http4s.server.blaze.WebSocketDecoder.sendInboundCommand(WebSocketDecoder.scala:14)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand(Stages.scala:276)
[info]  at org.http4s.blaze.pipeline.Head.inboundCommand$(Stages.scala:274)
[info]  at org.http4s.server.blaze.WebSocketDecoder.inboundCommand(WebSocketDecoder.scala:14)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand(Stages.scala:258)
[info]  at org.http4s.blaze.pipeline.Head.sendInboundCommand$(Stages.scala:254)
[info]  at org.http4s.blazecore.IdleTimeoutStage.sendInboundCommand(IdleTimeoutStage.scala:18)
[info]  at org.http4s.blaze.pipeline.Tail.replaceTail(Stages.scala:183)
[info]  at org.http4s.blaze.pipeline.Tail.replaceTail$(Stages.scala:162)
[info]  at org.http4s.server.blaze.Http1ServerStage.replaceTail(Http1ServerStage.scala:73)
[info]  at org.http4s.server.blaze.WebSocketSupport.$anonfun$renderResponse$7(WebSocketSupport.scala:83)
[info]  at scala.concurrent.impl.Promise$Transformation.run(Promise.scala:447)
[info]  at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
[info]  at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
[info]  at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
[info]  at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
[info]  at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.blaze.channel.nio1.NIO1HeadStage - Stage NIO1HeadStage sending inbound command: Disconnected
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.blazecore.IdleTimeoutStage - Shutting down idle timeout stage
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.blazecore.IdleTimeoutStage - Shutting down.
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.blazecore.IdleTimeoutStage - Stage IdleTimeoutStage sending inbound command: Disconnected
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.server.blaze.WebSocketDecoder - Shutting down.
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.server.blaze.WebSocketDecoder - Stage WebSocketDecoder sending inbound command: Disconnected
[info] 23:11:18.007 [blaze-selector-1] DEBUG org.http4s.server.blaze.WSFrameAggregator - Shutting down.
[info] 23:11:18.008 [blaze-selector-1] DEBUG org.http4s.server.blaze.WSFrameAggregator - Stage WSFrameAggregator sending inbound command: Disconnected
[info] 23:11:18.010 [blaze-selector-1] DEBUG org.http4s.blazecore.websocket.Http4sWSStage - Shutting down.

I tried debugging it for a the past 2 hours, but I’m not deep enough in the http4s codebase to resolve this within a reasonable amount of time. Hopeful the solution for this will be obvious to someone around here.

Issue Analytics

  • State:closed
  • Created 3 years ago
  • Reactions:2
  • Comments:16 (13 by maintainers)

github_iconTop GitHub Comments

1reaction
pjancommented, Sep 20, 2020

Given that we need both an F ~> G as well as a G ~>F for the transformation of the Pipe (inside the Websocket > WebsocketContext > Response) for this to work, it would still come with API breakage.

0reactions
armanbilgecommented, May 2, 2022
Read more comments on GitHub >

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