ZIO learning - implementing a backpressure queue / published by https://github.com/dacr/code-examples-manager #47acc4f4-4119-41b3-a337-a0999efa366c/1b22ea52b6e0377031528564894d59eced8cb5f0

zio-learning-21-back-pressured-queue.sc

// summary : ZIO learning - implementing a backpressure queue
// keywords : scala, zio, learning, pure-functional, backpressure, queue, @testable
// publish : gist
// authors : David Crosson
// license : Apache License Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0.txt)
// id : 47acc4f4-4119-41b3-a337-a0999efa366c
// created-on : 2021-04-06T15:32:12+02:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala "3.4.2"
//> using dep "dev.zio::zio:2.0.13"
// ---------------------

/*
 inspired from
   - [John A De Goes - ZIO: Next-Generation Effects in Scala](https://www.youtube.com/watch?v=mkSHhsJXjdc)
   - +39:00
 */

import zio.*

object Encapsulated extends ZIOAppDefault {

  // 500 producers, one consumer
  val logic = for {
    queue    <- Queue.bounded[String](100)
    producers = (1 to 500).map(id => queue.offer(s"42 from $id").forever)
    fiber    <- ZIO.forkAll(producers)
    consumer <- queue.take
                  .flatMap(v => Clock.sleep(10.millis).flatMap(_ => Console.printLine(s"$v")))
                  .forever
  } yield ()

  def run = logic.timeout(Duration.fromMillis(4000)) // Just to avoid this script to run infinitly...

  // back pressure is managed automatically for free !!!!
}
// -------------------------------------------------------------
Encapsulated.main(Array.empty)