fs2 chunkN vs groupWithin

chunkN

import $ivy.`co.fs2::fs2-core:1.0.0`

import fs2.{Stream, Pipe}
import fs2.concurrent.Queue
import cats.effect.{IO, ContextShift, Timer, Concurrent}

import scala.util.Random
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext

implicit val ec: ExecutionContext = ExecutionContext.global
implicit val timer: Timer[IO] = IO.timer(ec)
implicit val ioContextShift: ContextShift[IO] = IO.contextShift(ec)


def build(implicit F: Concurrent[IO]) = {
  for {
    queue <- Stream.eval(Queue.unbounded[IO, Int](F))
    s <- Stream(
           Stream.eval(IO(Random.nextInt)).repeat.take(18).evalMap(i => queue.enqueue1(i)).drain,
           queue.dequeue.chunkN(10).evalMap(i => IO(println(i))).drain).parJoinUnbounded
  } yield s
}


// Blocks current thread
build.compile.toList.unsafeRunSync


/* Output
 * @ build.compile.toList.unsafeRunSync
 * Chunk(-391833074, 614565068, 1936167563, -2119471686, -1857543124, -1900916042, 1353128895, 1889653573, 500392992, 2118924531)
 * ...
*/

groupWithin

import $ivy.`co.fs2::fs2-core:1.0.0`

import fs2.{Stream, Pipe}
import fs2.concurrent.Queue
import cats.effect.{IO, ContextShift, Timer, Concurrent}

import scala.util.Random
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext

implicit val ec: ExecutionContext = ExecutionContext.global
implicit val timer: Timer[IO] = IO.timer(ec)
implicit val ioContextShift: ContextShift[IO] = IO.contextShift(ec)


def build(implicit F: Concurrent[IO]) = {
  for {
    queue <- Stream.eval(Queue.unbounded[IO, Int](F))
    s <- Stream(
           Stream.eval(IO(Random.nextInt)).repeat.take(18).evalMap(i => queue.enqueue1(i)).drain,
           queue.dequeue.groupWithin(10, 10.seconds).evalMap(i => IO(println(i))).drain).parJoinUnbounded
  } yield s
}

// Blocks current thread
build.compile.toList.unsafeRunSync

/* Output
 * @ build.compile.toList.unsafeRunSync
 * Chunk(-1133522839, 1008897302, 940406286, -2062433713, -1028396178, -1171614910, 1890998151, 274740986, -1472404521, 1045040472)
 * ...after 10 seconds...
 * Chunk(-1330500851, -502124516, 1118085056, 1144331273, 1422450486, -1756001900, -308979842, 1989353154)
 * ...end of output
 */