playWsFutureSequence.sc

// see also https://www.implicitdef.com/2015/11/19/comparing-scala-http-client-libraries.html

// task: use the prime checker webservice
// https://github.com/LoyolaChicagoCode/primenumbers-spray-scala
// to count the number of primes within a given range

/* instructions: create a build.sbt file in your project root folder containing the following lines:

scalaVersion := "3.3.1"

Compile / scalacOptions ++= Seq(
  "-deprecation",
  "-feature",
  "-unchecked",
  "-Wvalue-discard",
  "-language:strictEquality",
  "-Yexplicit-nulls",
  "-Ysafe-init",
)

libraryDependencies ++= Seq(
  "com.typesafe.play" %% "play-ahc-ws-standalone" % "2.2.4",
  "org.slf4j"         % "slf4j-simple"            % "2.0.9"
)
*/


// then launch sbt console and paste the rest of the code in the resulting REPL
// it is best to do this section by section, not all at once, following the comments

// *** section 1 ***

import scala.util.Success
import scala.concurrent.Future
import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import scala.concurrent.ExecutionContext.Implicits.global
import play.api.libs.ws.ahc.StandaloneAhcWSClient

val system = ActorSystem("wsplay-example")
given ActorSystem = system
val wsClient = StandaloneAhcWSClient()

val urls = (10000000 to 10005000).map: n => 
  "https://primechecker.azurewebsites.net/api/isPrime?number=" + n

// *** section 2 ***

// Seq[Future[...]]
val requests = urls.map(u => wsClient.url(u).get())
val results = requests.map: f => 
  f.map: r => 
    r.status == 200
val resultsFailsafe = results.map: f =>
  f.recover: ex => 
    false

// Future[Seq[...]]
val f1 = Future.sequence(results)
val f2 = f1.map(r => r.count(identity))

// how are these two different?
val f3 = Future.sequence(resultsFailsafe)
val f4 = f3.map(r => r.count(identity))

// *** section 3 ***

// print final result
f2.foreach(println)
f4.foreach(println)

// *** section 4 ***

// meanwhile, can check repeatedly how many requests have completed
results.count(f => f.isCompleted)
resultsFailsafe.count(f => f.isCompleted)

// you can also (repeatedly) print the wrapped result in the foreground
f2.value
f4.value

// *** section 5 ***

// finally, exit the REPL using
system.terminate()
// and/or Ctrl-C

// IMPORTANT: The current web service instances are too responsive 
// for us to observe progress by repeating line 53 manually. 
// Instead, we can paste (in one piece) lines 42-53 followed by several repetitions of
//
// ; Thread.sleep(10) ; results.count: f => f.isCompleted
//
// to see progress in this form:
//
// val res75: Int = 105
// val res77: Int = 109
// ...
//
// If that's not enough, try redoing the whole experiment for a wider numeric range, 
// e.g., 10 or 100 times as wide.