Vertx RxScala Implementation

[willisjtc]

Do you plan on providing an rxscala toolkit for vertx applications? If so, would you want some assistance?

[willisjtc]

@vietj: Is this repo still active?

[vietj]

@willisjtc yes it is

[codepitbull]

I already played around with RxJava and here are my 2 cents: Both RxJava and RxJava2 are very Javaish libraries. That's the reason RxScala has been created. So for RxJava-integration I would recommend to not use RxJava directly but go to RxScala directly as it has a way more scalaish-API. RxJava2 is a different beast. There is no RxScala2 and (judging from the age of the last comment in this issue https://github.com/ReactiveX/RxScala/issues/227) there won't probably be one. Bith take quite a lot of work to integrate with Scala. I'd recommend to start with RxJava2 and skip RxJava altogether. What do you think?

[willisjtc]

Are you thinking of doing rxscala or rxjava2 first? I'd prefer starting with rxscala only because we use rxjava 1.0 at work and getting adoption would be easier on the same rx version. I'm totally fine either way, though.

[codepitbull]

The problem is: Both will take quite some work to get working. My tendency would be to go with RxJava2 as it is completely based on Reactive Streams and because of reactive-streams-commons (https://github.com/reactor/reactive-streams-commons) which would give us a ton of stages right from the start.

I'd still be open to also do RxScala but we will have to maintain both.

[willisjtc]

Any issues i could start working on?

[codepitbull]

Right now I'd like to work on https://github.com/vert-x3/vertx-lang-scala/issues/54 to be better prepared for Java 9 and changes cutting across different modules.

I am currently spending some time working with RxJava 2 and trying to find a way to integrate it and get some reuse from vertx-rxjava2.

[DavidGregory084]

@codepitbull have you considered using Monix? It's Reactive Streams compliant and has an idiomatic Scala API.

Wrapping AsyncResult handlers is as simple as this:

  // Decorate the Task companion object with a method for converting handler methods to Task
  implicit class MonixTaskCompanionVertxOps(task: Task.type) {
    def handle[A](f: Handler[AsyncResult[A]] => Unit): Task[A] = {
      def handler(cb: Callback[A]): Handler[AsyncResult[A]] = { result =>
        if (result.succeeded)
          cb.onSuccess(result.result)
        else
          cb.onError(result.cause)
      }

      def runnable(cb: Callback[A]): Runnable =
        () => try f(handler(cb)) catch {
          case NonFatal(e) => cb.onError(e)
        }

      Task.create { (s, cb) =>
        val scb = Callback.safe(cb)(s)
        s.execute(runnable(scb))
        Cancelable.empty
      }
    }
  }

  // Now every Handler[AsyncResult[A]] => Unit can be wrapped like this
  Task.handle[String] { handler =>
    vertx.deployVerticle(arg0, arg1, handler)
  }

or to convert ReadStream to an Observable:

  implicit class VertxReadStreamOps[A](readStream: ReadStream[A]) {
    def toObservable(vertx: Vertx): Observable[A] = {
      val writeStream = ReactiveWriteStream.writeStream[A](vertx)
      Pump.pump(readStream, writeStream).start()
      readStream.endHandler(_ => writeStream.end())
      Observable.fromReactivePublisher(writeStream)
    }
  }

  val stream = vertx.eventBus
    .consumer[String](address)
    .toObservable(vertx)

[codepitbull]

That's very nice. I looked at Monix for quite a while ago for another project. Completely forgot about it. I hope it's ok if I steal your code snippet :)

[DavidGregory084]

Yep, sure, I've actually been messing around with generating wrapper APIs to use with Monix here if you want to see what this might look like

[codepitbull]

@DavidGregory084 I've been working on and off on a value classes based approach to integrating Vert.x and Scala. The current (working) results are here https://github.com/codepitbull/vertx-lang-scala-vc It also contains adapters for RxJava2, some small experiments of doing streams myself and it might be a good place to add Monix support.

[DavidGregory084]

@codepitbull I finally got back to experimenting with this idea again here: https://github.com/DavidGregory084/vertices

It uses the value classes / implicit class based approach just like your repo. One thing that is a little awkward is that you can't add extension methods to Java so that they are callable like static methods, the way that you can with scala companion objects.

I have used the vertx-codegen code in order to generate extension methods for all of the vertx APIs, although my approach is a little mechanical and it can get things wrong, such as generating Task methods for methods which set a callback rather than ones which pass the callback in order to receive a result.

[codepitbull]

@DavidGregory084 you might want to check the current state of vertx-lang-scala. The master branch now contains a full implementation of my approach and you might be able to grab a lot of stuff from there since I already get all the methods from the Java-API for conversion. If it helps, I could extract a lot of the conversion code if you assist me so we could create a shared codebase to handle your scenario. My current plan is to finalize work next week during my vacation and then start working on the reactive streams adapters.