how does rho handle websocket about rho

[shengc]

coming up with an ugly hack for websocket ...

 import org.http4s.server.websocket._
 import org.http4s.websocket.WebsocketBits._

 val src = Process.constant("test").toSource.zipWithIndex.map({ case (msg, i) => Text(s"$msg - $i") })take(20)
 val snk = Process.halt

 // unfortunately websocketkey and websocket case class are both defined in a protected scope that as a user cannot access
 val attrs = WS(Exchange(src, snk)).run.attributes.entries.toList
 attrs.foldLeft(NotImplemented("this is a websocket route"))(_.withAttribute(_))

Besides exposing too many internal logic, this solution does not allow response evaluated in a separate thread pool. In normal HttpService, I can use Task.fork to easily run the response in a different thread pool, but with rho dsl, there seems to be no easy to achieve the same effect.

[bryce-anderson]

I have given no consideration to websockets in rho as of yet.

The problem shouldn't be the Task but the Response: who deals in Results to keep some compile time information around for use in swagger generation etc, which is just a wrapper around Response with some extra type information.

[bryce-anderson]

@shengc, I have a PR to address this, but I'm not sure when it will hit a release. In the intrum, you could copy the ResultMatcher code and bring the implicit into scope manually.

[shengc]

@bryce-anderson,

I think I got what you mean. I have rewritten the solution I came up with, which now seems more reasonable ...

Task.fork {
   import org.http4s.server.websocket._
   import org.http4s.websocket.WebsocketBits._

   val src = Process.constant("test").toSource.zipWithIndex.map({ case (msg, i) => Text(s"$msg - $i") })take(20)
   val snk = Process.halt

   WS(Exchange(src, snk)).flatMap(_.attributes.entries.foldLeft(NotImplemented("this is a websocket route"))(_.withAttribute(_)))
}

[shengc]

@bryce-anderson, yes that result matcher definitely is helpful :-)

[shengc]

This raises another problem though. Look at this example,

GET / "number" +? param[Int]("num") |>> { (num: Int) =>
  if (num < 0) BadRequest("num <= 0 :-(")
  else WS(Exchange(Process.constant("test").take(num).map(Text(_)), Process.halt))
}

The implicits get messed up in this case, since BadRequest does not get resolved to a Task[Response]. The only workaround I have for this is to explicitly use org.http4s.dsl.BadRequest(...) so that an implicit ResultMatcher[Response] can be resolved. It is definitely an unpleasant hack, wondering if there is a more natural way to address this ?

[bryce-anderson]

There is no easy way to make the types unify there. What you've done is the best we can do with the current state of affairs. To make it better, rho will need to get a first class notion of WS.

[bryce-anderson]

I do remember another way you can make this work, but you lose any swagger information (if you were using it at all): try BadRequest.pure("num <= 0 :-("). that will make a Task[Response] instead of a Task[Result] and will match the WS result type.

[shengc]

Thanks :) Does swagger support websocket anyway ?

[bryce-anderson]

Nope.

On Wed, Jul 15, 2015 at 8:57 PM, Mianwo [email protected] wrote:

Thanks :) Does swagger support websocket anyway ?

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