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Stream - Refactor Parjoins #3248

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Jul 27, 2023
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Stream - Refactor Parjoins #3248

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118 changes: 41 additions & 77 deletions core/shared/src/main/scala/fs2/Stream.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -2155,34 +2155,23 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
*/
def parEvalMap[F2[x] >: F[x], O2](
maxConcurrent: Int
)(f: O => F2[O2])(implicit F: Concurrent[F2]): Stream[F2, O2] = {

def init(ch: Channel[F2, F2[Either[Throwable, O2]]], release: F2[Unit]) =
Deferred[F2, Either[Throwable, O2]].flatTap { value =>
ch.send(release *> value.get)
}

def send(v: Deferred[F2, Either[Throwable, O2]]) =
(el: Either[Throwable, O2]) => v.complete(el).void

parEvalMapAction(maxConcurrent, f)((ch, release) => init(ch, release).map(send))
}
)(f: O => F2[O2])(implicit F: Concurrent[F2]): Stream[F2, O2] =
if (maxConcurrent == 1) evalMap(f)
else {
assert(maxConcurrent > 0, "maxConcurrent must be > 0, was: " + maxConcurrent)
// One is taken by inner stream read.
val concurrency = if (maxConcurrent == Int.MaxValue) Int.MaxValue else maxConcurrent + 1
val channelF = Channel.bounded[F2, F2[Either[Throwable, O2]]](concurrency)
parEvalMapActionImpl[F2, O2](concurrency.toLong, channelF, true, f)
}

/** Like parEvalMap but with unbounded concurrency.
*/
def parEvalMapUnbounded[F2[x] >: F[x], O2](f: O => F2[O2])(implicit
F: Concurrent[F2]
): Stream[F2, O2] = {

def init(ch: Channel[F2, F2[Either[Throwable, O2]]], release: F2[Unit]) =
Deferred[F2, Either[Throwable, O2]].flatTap { value =>
ch.send(release *> value.get)
}

def send(v: Deferred[F2, Either[Throwable, O2]]) =
(el: Either[Throwable, O2]) => v.complete(el).void

parEvalMapUnboundedAction(f)((ch, release) => init(ch, release).map(send))
val channelF = Channel.unbounded[F2, F2[Either[Throwable, O2]]]
parEvalMapActionImpl(Long.MaxValue, channelF, true, f)
}

/** Like [[Stream#evalMap]], but will evaluate effects in parallel, emitting the results
Expand All @@ -2198,71 +2187,30 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
*/
def parEvalMapUnordered[F2[x] >: F[x], O2](
maxConcurrent: Int
)(f: O => F2[O2])(implicit F: Concurrent[F2]): Stream[F2, O2] = {

def send(ch: Channel[F2, F2[Either[Throwable, O2]]], release: F2[Unit]) =
(el: Either[Throwable, O2]) => release <* ch.send(el.pure[F2])

parEvalMapAction(maxConcurrent, f)((ch, release) => send(ch, release).pure[F2])
}

/** Like parEvalMapUnordered but with unbounded concurrency.
*/
def parEvalMapUnorderedUnbounded[F2[x] >: F[x], O2](
f: O => F2[O2]
)(implicit F: Concurrent[F2]): Stream[F2, O2] = {

def send(ch: Channel[F2, F2[Either[Throwable, O2]]], release: F2[Unit]) =
(el: Either[Throwable, O2]) => release <* ch.send(el.pure[F2])

parEvalMapUnboundedAction(f)((ch, release) => send(ch, release).pure[F2])
}

private def parEvalMapAction[F2[x] >: F[x], O2, T](
maxConcurrent: Int,
f: O => F2[O2]
)(
initFork: (
Channel[F2, F2[Either[Throwable, O2]]],
F2[Unit]
) => F2[Either[Throwable, O2] => F2[Unit]]
)(implicit F: Concurrent[F2]): Stream[F2, O2] =
)(f: O => F2[O2])(implicit F: Concurrent[F2]): Stream[F2, O2] =
if (maxConcurrent == 1) evalMap(f)
else {
assert(maxConcurrent > 0, "maxConcurrent must be > 0, was: " + maxConcurrent)

// One is taken by inner stream read.
val concurrency = if (maxConcurrent == Int.MaxValue) Int.MaxValue else maxConcurrent + 1
parEvalMapActionImpl[F2, O2, T](
concurrency.toLong,
Channel.bounded[F2, F2[Either[Throwable, O2]]](concurrency),
f
)(initFork)
val channelF = Channel.bounded[F2, F2[Either[Throwable, O2]]](concurrency)
parEvalMapActionImpl[F2, O2](concurrency.toLong, channelF, false, f)
}

private def parEvalMapUnboundedAction[F2[x] >: F[x], O2, T](
/** Like parEvalMapUnordered but with unbounded concurrency.
*/
def parEvalMapUnorderedUnbounded[F2[x] >: F[x], O2](
f: O => F2[O2]
)(
initFork: (
Channel[F2, F2[Either[Throwable, O2]]],
F2[Unit]
) => F2[Either[Throwable, O2] => F2[Unit]]
)(implicit F: Concurrent[F2]): Stream[F2, O2] =
parEvalMapActionImpl(
Long.MaxValue,
Channel.unbounded[F2, F2[Either[Throwable, O2]]],
f
)(initFork)

private def parEvalMapActionImpl[F2[x] >: F[x], O2, T](
)(implicit F: Concurrent[F2]): Stream[F2, O2] = {
val channelF = Channel.unbounded[F2, F2[Either[Throwable, O2]]]
parEvalMapActionImpl(Long.MaxValue, channelF, false, f)
}

private def parEvalMapActionImpl[F2[x] >: F[x], O2](
concurrency: Long,
channel: F2[Channel[F2, F2[Either[Throwable, O2]]]],
isOrdered: Boolean,
f: O => F2[O2]
)(
initFork: (
Channel[F2, F2[Either[Throwable, O2]]],
F2[Unit]
) => F2[Either[Throwable, O2] => F2[Unit]]
)(implicit F: Concurrent[F2]): Stream[F2, O2] = {
val action =
(
Expand All @@ -2271,6 +2219,22 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
Deferred[F2, Unit],
Deferred[F2, Unit]
).mapN { (semaphore, channel, stop, end) =>
def initFork(release: F2[Unit]): F2[Either[Throwable, O2] => F2[Unit]] = {
def ordered: F2[Either[Throwable, O2] => F2[Unit]] = {
def send(v: Deferred[F2, Either[Throwable, O2]]) =
(el: Either[Throwable, O2]) => v.complete(el).void

Deferred[F2, Either[Throwable, O2]]
.flatTap(value => channel.send(release *> value.get))
.map(send)
}

def unordered: Either[Throwable, O2] => F2[Unit] =
(el: Either[Throwable, O2]) => release <* channel.send(F.pure(el))

if (isOrdered) ordered else F.pure(unordered)
}

val releaseAndCheckCompletion =
semaphore.release *>
semaphore.available.flatMap {
Expand All @@ -2282,7 +2246,7 @@ final class Stream[+F[_], +O] private[fs2] (private[fs2] val underlying: Pull[F,
F.uncancelable { poll =>
poll(semaphore.acquire) <*
Deferred[F2, Unit].flatMap { pushed =>
val init = initFork(channel, pushed.complete(()).void)
val init = initFork(pushed.complete(()).void)
poll(init).onCancel(releaseAndCheckCompletion).flatMap { send =>
val action = F.catchNonFatal(f(el)).flatten.attempt.flatMap(send) *> pushed.get
F.start(stop.get.race(action) *> releaseAndCheckCompletion)
Expand Down