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GenSpawn.scala
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GenSpawn.scala
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/*
* Copyright 2020-2023 Typelevel
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cats.effect.kernel
import cats.{~>, Applicative, Monoid, Semigroup}
import cats.data.{EitherT, Ior, IorT, Kleisli, OptionT, WriterT}
import cats.effect.kernel.syntax.monadCancel._
import cats.syntax.all._
/**
* A typeclass that characterizes monads which support spawning and racing of fibers.
* [[GenSpawn]] extends the capabilities of [[MonadCancel]], so an instance of this typeclass
* must also provide a lawful instance for [[MonadCancel]].
*
* This documentation builds upon concepts introduced in the [[MonadCancel]] documentation.
*
* ==Concurrency==
*
* [[GenSpawn]] introduces a notion of concurrency that enables fibers to safely interact with
* each other via three special functions. [[GenSpawn!.start start]] spawns a fiber that
* executes concurrently with the spawning fiber. [[Fiber!.join join]] semantically blocks the
* joining fiber until the joinee fiber terminates, after which the [[Outcome]] of the joinee is
* returned. [[Fiber!.cancel cancel]] requests a fiber to abnormally terminate, and semantically
* blocks the canceller until the cancellee has completed finalization.
*
* Just like threads, fibers can execute concurrently with respect to each other. This means
* that the effects of independent fibers may be interleaved nondeterministically. This mode of
* concurrency reaps benefits for modular program design; fibers that are described separately
* can execute simultaneously without requiring programmers to explicitly yield back to the
* runtime system.
*
* The interleaving of effects is illustrated in the following program:
*
* {{{
*
* for {
* fa <- (println("A1") *> println("A2")).start
* fb <- (println("B1") *> println("B2")).start
* } yield ()
*
* }}}
*
* In this program, two fibers A and B are spawned concurrently. There are six possible
* executions, each of which exhibits a different ordering of effects. The observed output of
* each execution is shown below:
*
* 1. A1, A2, B1, B2
* 1. A1, B1, A2, B2
* 1. A1, B1, B2, A2
* 1. B1, B2, A1, A2
* 1. B1, A1, B2, A2
* 1. B1, A1, A2, B2
*
* Notice how every execution preserves sequential consistency of the effects within each fiber:
* `A1` always prints before `A2`, and `B1` always prints before `B2`. However, there are no
* guarantees around how the effects of both fibers will be ordered with respect to each other;
* it is entirely nondeterministic.
*
* ==Cancelation==
*
* [[MonadCancel]] introduces a simple means of cancelation, particularly self-cancelation,
* where a fiber can request the abnormal termination of its own execution. This is achieved by
* calling [[MonadCancel!.canceled canceled]].
*
* [[GenSpawn]] expands on the cancelation model described by [[MonadCancel]] by introducing a
* means of external cancelation. With external cancelation, a fiber can request the abnormal
* termination of another fiber by calling [[Fiber!.cancel]].
*
* The cancelation model dictates that external cancelation behaves identically to
* self-cancelation. To guarantee consistent behavior between the two, the following semantics
* are shared:
*
* 1. Masking: if a fiber is canceled while it is masked, cancelation is suppressed until it
* reaches a completely unmasked state. See [[MonadCancel]] documentation for more details.
* 1. Backpressure: [[Fiber!.cancel cancel]] semantically blocks all callers until
* finalization is complete.
* 1. Idempotency: once a fiber's cancelation has been requested, subsequent cancelations have
* no effect on cancelation status.
* 1. Terminal: Cancelation of a fiber that has terminated immediately returns.
*
* External cancelation contrasts with self-cancelation in one aspect: the former may require
* synchronization between multiple threads to communicate a cancelation request. As a result,
* cancelation may not be immediately observed by a fiber. Implementations are free to decide
* how and when this synchronization takes place.
*
* ==Cancelation safety==
*
* A function or effect is considered to be cancelation-safe if it can be run in the absence of
* masking without violating effectful lifecycles or leaking resources. These functions require
* extra attention and care from users to ensure safe usage.
*
* [[start]] and [[racePair]] are both considered to be cancelation-unsafe effects because they
* return a [[Fiber]], which is a resource that has a lifecycle.
*
* {{{
*
* // Start a fiber that continuously prints "A".
* // After 10 seconds, cancel the fiber.
* F.start(F.delay(println("A")).foreverM).flatMap { fiber =>
* F.sleep(10.seconds) *> fiber.cancel
* }
*
* }}}
*
* In the above example, imagine the spawning fiber is canceled after it starts the printing
* fiber, but before the latter is canceled. In this situation, the printing fiber is not
* canceled and will continue executing forever, contending with other fibers for system
* resources. Fiber leaks like this typically happen because some fiber that holds a reference
* to a child fiber is canceled before the child terminates; like threads, fibers will not
* automatically be cleaned up.
*
* Resource leaks like this are unfavorable when writing applications. In the case of [[start]]
* and [[racePair]], it is recommended not to use these methods; instead, use [[background]] and
* [[race]] respectively.
*
* The following example depicts a safer version of the [[start]] example above:
*
* {{{
*
* // Starts a fiber that continously prints "A".
* // After 10 seconds, the resource scope exits so the fiber is canceled.
* F.background(F.delay(println("A")).foreverM).use { _ =>
* F.sleep(10.seconds)
* }
*
* }}}
*
* ==Scheduling==
*
* Fibers are commonly referred to as ''lightweight threads'' or ''green threads''. This alludes
* to the nature by which fibers are scheduled by runtime systems: many fibers are multiplexed
* onto one or more native threads.
*
* For applications running on the JVM, the scheduler typically manages a thread pool onto which
* fibers are scheduled. These fibers are executed simultaneously by the threads in the pool,
* achieving both concurrency and parallelism. For applications running on JavaScript platforms,
* all compute is restricted to a single worker thread, so multiple fibers must share that
* worker thread (dictated by fairness properties), achieving concurrency without parallelism.
*
* [[cede]] is a special function that interacts directly with the underlying scheduler. It is a
* means of cooperative multitasking by which a fiber signals to the runtime system that it
* intends to pause execution and resume at some later time at the discretion of the scheduler.
* This is in contrast to preemptive multitasking, in which threads of control are forcibly
* yielded after a well-defined time slice.
*
* Preemptive and cooperative multitasking are both features of runtime systems that influence
* the fairness and throughput properties of an application. These modes of scheduling are not
* necessarily mutually exclusive: a runtime system may incorporate a blend of the two, where
* fibers can explicitly yield back to the scheduler, but the runtime preempts a fiber if it has
* not yielded for some time.
*
* For more details on schedulers, see the following resources:
*
* 1. https://gist.github.com/djspiewak/3ac3f3f55a780e8ab6fa2ca87160ca40
* 1. https://gist.github.com/djspiewak/46b543800958cf61af6efa8e072bfd5c
*/
trait GenSpawn[F[_], E] extends MonadCancel[F, E] with Unique[F] {
implicit private[this] def F: MonadCancel[F, E] = this
def applicative: Applicative[F] = this
final def rootCancelScope: CancelScope = CancelScope.Cancelable
/**
* A low-level primitive for starting the concurrent evaluation of a fiber. Returns a
* [[Fiber]] that can be used to wait for a fiber or cancel it.
*
* [[start]] is a cancelation-unsafe function; it is recommended to use the safer variant,
* [[background]], to spawn fibers.
*
* @param fa
* the effect for the fiber
*
* @see
* [[background]] for the safer, recommended variant
*/
def start[A](fa: F[A]): F[Fiber[F, E, A]]
/**
* Returns a [[Resource]] that manages the concurrent execution of a fiber. The inner effect
* can be used to wait on the outcome of the child fiber; it is effectively a
* [[Fiber!.join join]].
*
* The child fiber is canceled in two cases: either the resource goes out of scope or the
* parent fiber is canceled. If the child fiber terminates before one of these cases occurs,
* then cancelation is a no-op. This avoids fiber leaks because the child fiber is always
* canceled before the parent fiber drops the reference to it.
*
* {{{
*
* // Starts a fiber that continously prints "A".
* // After 10 seconds, the resource scope exits so the fiber is canceled.
* F.background(F.delay(println("A")).foreverM).use { _ =>
* F.sleep(10.seconds)
* }
*
* }}}
*
* @param fa
* the effect for the spawned fiber
*/
def background[A](fa: F[A]): Resource[F, F[Outcome[F, E, A]]] =
Resource.make(start(fa))(_.cancel)(this).map(_.join)
/**
* A non-terminating effect that never completes, which causes a fiber to semantically block
* indefinitely. This is the purely functional, asynchronous equivalent of an infinite while
* loop in Java, but no native threads are blocked.
*
* A fiber that is suspended in [[never]] can be canceled if it is completely unmasked before
* it suspends:
*
* {{{
*
* // ignoring race conditions between `start` and `cancel`
* F.never.start.flatMap(_.cancel) <-> F.unit
*
* }}}
*
* However, if the fiber is masked, cancellers will be semantically blocked forever:
*
* {{{
*
* // ignoring race conditions between `start` and `cancel`
* F.uncancelable(_ => F.never).start.flatMap(_.cancel) <-> F.never
*
* }}}
*/
def never[A]: F[A]
/**
* Introduces a fairness boundary that yields control back to the scheduler of the runtime
* system. This allows the carrier thread to resume execution of another waiting fiber.
*
* This function is primarily useful when performing long-running computation that is outside
* of the monadic context. For example:
*
* {{{
* fa.map(data => expensiveWork(data))
* }}}
*
* In the above, we're assuming that `expensiveWork` is a function which is entirely
* compute-bound but very long-running. A good rule of thumb is to consider a function
* "expensive" when its runtime is around three or more orders of magnitude higher than the
* overhead of the `map` function itself (which runs in around 5 nanoseconds on modern
* hardware). Thus, any `expensiveWork` function which requires around 10 microseconds or
* longer to execute should be considered "long-running".
*
* The danger is that these types of long-running actions outside of the monadic context can
* result in degraded fairness properties. The solution is to add an explicit `cede` both
* before and after the expensive operation:
*
* {{{
* (fa <* F.cede).map(data => expensiveWork(data)).guarantee(F.cede)
* }}}
*
* Note that extremely long-running `expensiveWork` functions can still cause fairness issues,
* even when used with `cede`. This problem is somewhat fundamental to the nature of
* scheduling such computation on carrier threads. Whenever possible, it is best to break
* apart any such functions into multiple pieces invoked independently (e.g. via chained `map`
* calls) whenever the execution time exceeds five or six orders of magnitude beyond the
* overhead of `map` itself (around 1 millisecond on most hardware).
*
* Note that `cede` is merely a hint to the runtime system; implementations have the liberty
* to interpret this method to their liking as long as it obeys the respective laws. For
* example, a lawful, but atypical, implementation of this function is `F.unit`, in which case
* the fairness boundary is a no-op.
*/
def cede: F[Unit]
/**
* A low-level primitive for racing the evaluation of two fibers that returns the [[Outcome]]
* of the winner and the [[Fiber]] of the loser. The winner of the race is considered to be
* the first fiber that completes with an outcome.
*
* [[racePair]] is a cancelation-unsafe function; it is recommended to use the safer variants.
*
* @param fa
* the effect for the first racing fiber
* @param fb
* the effect for the second racing fiber
*
* @see
* [[raceOutcome]] and [[race]] for safer race variants.
*/
def racePair[A, B](fa: F[A], fb: F[B])
: F[Either[(Outcome[F, E, A], Fiber[F, E, B]), (Fiber[F, E, A], Outcome[F, E, B])]]
/**
* Races the evaluation of two fibers that returns the [[Outcome]] of the winner. The winner
* of the race is considered to be the first fiber that completes with an outcome. The loser
* of the race is canceled before returning.
*
* @param fa
* the effect for the first racing fiber
* @param fb
* the effect for the second racing fiber
*
* @see
* [[race]] for a simpler variant that returns the successful outcome.
*/
def raceOutcome[A, B](fa: F[A], fb: F[B]): F[Either[Outcome[F, E, A], Outcome[F, E, B]]] =
uncancelable { poll =>
poll(racePair(fa, fb)).flatMap {
case Left((oc, f)) => f.cancel.as(Left(oc))
case Right((f, oc)) => f.cancel.as(Right(oc))
}
}
/**
* Races the evaluation of two fibers that returns the result of the winner, except in the
* case of cancelation.
*
* The semantics of [[race]] are described by the following rules:
*
* 1. If the winner completes with [[Outcome.Succeeded]], the race returns the successful
* value. The loser is canceled before returning. 2. If the winner completes with
* [[Outcome.Errored]], the race raises the error. The loser is canceled before
* returning. 3. If the winner completes with [[Outcome.Canceled]], the race returns the
* result of the loser, consistent with the first two rules. 4. If both the winner and
* loser complete with [[Outcome.Canceled]], the race is canceled. 8. If the race is
* masked and is canceled because both participants canceled, the fiber will block
* indefinitely.
*
* @param fa
* the effect for the first racing fiber
* @param fb
* the effect for the second racing fiber
*
* @see
* [[raceOutcome]] for a variant that returns the outcome of the winner.
*/
def race[A, B](fa: F[A], fb: F[B]): F[Either[A, B]] =
uncancelable { poll =>
poll(racePair(fa, fb)).flatMap {
case Left((oc, f)) =>
oc match {
case Outcome.Succeeded(fa) => f.cancel *> fa.map(Left(_))
case Outcome.Errored(ea) => f.cancel *> raiseError(ea)
case Outcome.Canceled() =>
poll(f.join).onCancel(f.cancel).flatMap {
case Outcome.Succeeded(fb) => fb.map(Right(_))
case Outcome.Errored(eb) => raiseError(eb)
case Outcome.Canceled() => poll(canceled) *> never
}
}
case Right((f, oc)) =>
oc match {
case Outcome.Succeeded(fb) => f.cancel *> fb.map(Right(_))
case Outcome.Errored(eb) => f.cancel *> raiseError(eb)
case Outcome.Canceled() =>
poll(f.join).onCancel(f.cancel).flatMap {
case Outcome.Succeeded(fa) => fa.map(Left(_))
case Outcome.Errored(ea) => raiseError(ea)
case Outcome.Canceled() => poll(canceled) *> never
}
}
}
}
/**
* Races the evaluation of two fibers and returns the [[Outcome]] of both. If the race is
* canceled before one or both participants complete, then then whichever ones are incomplete
* are canceled.
*
* @param fa
* the effect for the first racing fiber
* @param fb
* the effect for the second racing fiber
*
* @see
* [[both]] for a simpler variant that returns the results of both fibers.
*/
def bothOutcome[A, B](fa: F[A], fb: F[B]): F[(Outcome[F, E, A], Outcome[F, E, B])] =
uncancelable { poll =>
poll(racePair(fa, fb)).flatMap {
case Left((oc, f)) => poll(f.join).onCancel(f.cancel).tupleLeft(oc)
case Right((f, oc)) => poll(f.join).onCancel(f.cancel).tupleRight(oc)
}
}
/**
* Races the evaluation of two fibers and returns the result of both.
*
* The following rules describe the semantics of [[both]]:
*
* 1. If the winner completes with [[Outcome.Succeeded]], the race waits for the loser to
* complete. 2. If the winner completes with [[Outcome.Errored]], the race raises the
* error. The loser is canceled. 3. If the winner completes with [[Outcome.Canceled]],
* the loser and the race are canceled as well. 4. If the loser completes with
* [[Outcome.Succeeded]], the race returns the successful value of both fibers. 5. If the
* loser completes with [[Outcome.Errored]], the race returns the error. 6. If the loser
* completes with [[Outcome.Canceled]], the race is canceled. 7. If the race is canceled
* before one or both participants complete, then whichever ones are incomplete are
* canceled. 8. If the race is masked and is canceled because one or both participants
* canceled, the fiber will block indefinitely.
*
* @param fa
* the effect for the first racing fiber
* @param fb
* the effect for the second racing fiber
*
* @see
* [[bothOutcome]] for a variant that returns the [[Outcome]] of both fibers.
*/
def both[A, B](fa: F[A], fb: F[B]): F[(A, B)] =
uncancelable { poll =>
poll(racePair(fa, fb)).flatMap {
case Left((oc, f)) =>
oc match {
case Outcome.Succeeded(fa) =>
poll(f.join).onCancel(f.cancel).flatMap {
case Outcome.Succeeded(fb) => fa.product(fb)
case Outcome.Errored(eb) => raiseError(eb)
case Outcome.Canceled() => poll(canceled) *> never
}
case Outcome.Errored(ea) => f.cancel *> raiseError(ea)
case Outcome.Canceled() => f.cancel *> poll(canceled) *> never
}
case Right((f, oc)) =>
oc match {
case Outcome.Succeeded(fb) =>
poll(f.join).onCancel(f.cancel).flatMap {
case Outcome.Succeeded(fa) => fa.product(fb)
case Outcome.Errored(ea) => raiseError(ea)
case Outcome.Canceled() => poll(canceled) *> never
}
case Outcome.Errored(eb) => f.cancel *> raiseError(eb)
case Outcome.Canceled() => f.cancel *> poll(canceled) *> never
}
}
}
}
object GenSpawn {
import MonadCancel.{
EitherTMonadCancel,
IorTMonadCancel,
KleisliMonadCancel,
OptionTMonadCancel,
WriterTMonadCancel
}
def apply[F[_], E](implicit F: GenSpawn[F, E]): F.type = F
def apply[F[_]](implicit F: GenSpawn[F, _], d: DummyImplicit): F.type = F
implicit def genSpawnForOptionT[F[_], E](
implicit F0: GenSpawn[F, E]): GenSpawn[OptionT[F, *], E] =
F0 match {
case async: Async[F @unchecked] =>
Async.asyncForOptionT[F](async)
case temporal: GenTemporal[F @unchecked, E @unchecked] =>
GenTemporal.instantiateGenTemporalForOptionT[F, E](temporal)
case concurrent: GenConcurrent[F @unchecked, E @unchecked] =>
GenConcurrent.instantiateGenConcurrentForOptionT[F, E](concurrent)
case spawn =>
instantiateGenSpawnForOptionT(spawn)
}
private[kernel] def instantiateGenSpawnForOptionT[F[_], E](
F0: GenSpawn[F, E]): OptionTGenSpawn[F, E] =
new OptionTGenSpawn[F, E] {
override implicit protected def F: GenSpawn[F, E] = F0
}
implicit def genSpawnForEitherT[F[_], E0, E](
implicit F0: GenSpawn[F, E]): GenSpawn[EitherT[F, E0, *], E] =
F0 match {
case async: Async[F @unchecked] =>
Async.asyncForEitherT[F, E0](async)
case temporal: GenTemporal[F @unchecked, E @unchecked] =>
GenTemporal.instantiateGenTemporalForEitherT[F, E0, E](temporal)
case concurrent: GenConcurrent[F @unchecked, E @unchecked] =>
GenConcurrent.instantiateGenConcurrentForEitherT[F, E0, E](concurrent)
case spawn =>
instantiateGenSpawnForEitherT(spawn)
}
private[kernel] def instantiateGenSpawnForEitherT[F[_], E0, E](
F0: GenSpawn[F, E]): EitherTGenSpawn[F, E0, E] =
new EitherTGenSpawn[F, E0, E] {
override implicit protected def F: GenSpawn[F, E] = F0
}
implicit def genSpawnForKleisli[F[_], R, E](
implicit F0: GenSpawn[F, E]): GenSpawn[Kleisli[F, R, *], E] =
F0 match {
case async: Async[F @unchecked] =>
Async.asyncForKleisli[F, R](async)
case temporal: GenTemporal[F @unchecked, E @unchecked] =>
GenTemporal.instantiateGenTemporalForKleisli[F, R, E](temporal)
case concurrent: GenConcurrent[F @unchecked, E @unchecked] =>
GenConcurrent.instantiateGenConcurrentForKleisli[F, R, E](concurrent)
case spawn =>
instantiateGenSpawnForKleisli(spawn)
}
private[kernel] def instantiateGenSpawnForKleisli[F[_], R, E](
F0: GenSpawn[F, E]): KleisliGenSpawn[F, R, E] =
new KleisliGenSpawn[F, R, E] {
override implicit protected def F: GenSpawn[F, E] = F0
}
implicit def genSpawnForIorT[F[_], L, E](
implicit F0: GenSpawn[F, E],
L0: Semigroup[L]): GenSpawn[IorT[F, L, *], E] =
F0 match {
case async: Async[F @unchecked] =>
Async.asyncForIorT[F, L](async, L0)
case temporal: GenTemporal[F @unchecked, E @unchecked] =>
GenTemporal.instantiateGenTemporalForIorT[F, L, E](temporal)
case concurrent: GenConcurrent[F @unchecked, E @unchecked] =>
GenConcurrent.instantiateGenConcurrentForIorT[F, L, E](concurrent)
case spawn =>
instantiateGenSpawnForIorT(spawn)
}
private[kernel] def instantiateGenSpawnForIorT[F[_], L, E](F0: GenSpawn[F, E])(
implicit L0: Semigroup[L]): IorTGenSpawn[F, L, E] =
new IorTGenSpawn[F, L, E] {
override implicit protected def F: GenSpawn[F, E] = F0
override implicit protected def L: Semigroup[L] = L0
}
implicit def genSpawnForWriterT[F[_], L, E](
implicit F0: GenSpawn[F, E],
L0: Monoid[L]): GenSpawn[WriterT[F, L, *], E] =
F0 match {
case async: Async[F @unchecked] =>
Async.asyncForWriterT[F, L](async, L0)
case temporal: GenTemporal[F @unchecked, E @unchecked] =>
GenTemporal.instantiateGenTemporalForWriterT[F, L, E](temporal)
case concurrent: GenConcurrent[F @unchecked, E @unchecked] =>
GenConcurrent.instantiateGenConcurrentForWriterT[F, L, E](concurrent)
case spawn =>
instantiateGenSpawnForWriterT(spawn)
}
private[kernel] def instantiateGenSpawnForWriterT[F[_], L, E](F0: GenSpawn[F, E])(
implicit L0: Monoid[L]): WriterTGenSpawn[F, L, E] =
new WriterTGenSpawn[F, L, E] {
override implicit protected def F: GenSpawn[F, E] = F0
override implicit protected def L: Monoid[L] = L0
}
private[kernel] trait OptionTGenSpawn[F[_], E]
extends GenSpawn[OptionT[F, *], E]
with OptionTMonadCancel[F, E] {
implicit protected def F: GenSpawn[F, E]
def unique: OptionT[F, Unique.Token] =
OptionT.liftF(F.unique)
def start[A](fa: OptionT[F, A]): OptionT[F, Fiber[OptionT[F, *], E, A]] =
OptionT.liftF(F.start(fa.value).map(liftFiber))
def never[A]: OptionT[F, A] = OptionT.liftF(F.never)
def cede: OptionT[F, Unit] = OptionT.liftF(F.cede)
def racePair[A, B](fa: OptionT[F, A], fb: OptionT[F, B]): OptionT[
F,
Either[
(Outcome[OptionT[F, *], E, A], Fiber[OptionT[F, *], E, B]),
(Fiber[OptionT[F, *], E, A], Outcome[OptionT[F, *], E, B])]] = {
OptionT.liftF(F.uncancelable(poll =>
poll(F.racePair(fa.value, fb.value)).map {
case Left((oc, fib)) => Left((liftOutcome(oc), liftFiber(fib)))
case Right((fib, oc)) => Right((liftFiber(fib), liftOutcome(oc)))
}))
}
override def race[A, B](fa: OptionT[F, A], fb: OptionT[F, B]): OptionT[F, Either[A, B]] =
OptionT(F.race(fa.value, fb.value).map(_.bisequence))
override def both[A, B](fa: OptionT[F, A], fb: OptionT[F, B]): OptionT[F, (A, B)] =
OptionT(F.both(fa.value, fb.value).map(_.tupled))
override def raceOutcome[A, B](fa: OptionT[F, A], fb: OptionT[F, B])
: OptionT[F, Either[Outcome[OptionT[F, *], E, A], Outcome[OptionT[F, *], E, B]]] =
OptionT.liftF(
F.raceOutcome(fa.value, fb.value).map(_.bimap(liftOutcome(_), liftOutcome(_))))
override def bothOutcome[A, B](fa: OptionT[F, A], fb: OptionT[F, B])
: OptionT[F, (Outcome[OptionT[F, *], E, A], Outcome[OptionT[F, *], E, B])] =
OptionT.liftF(
F.bothOutcome(fa.value, fb.value).map(_.bimap(liftOutcome(_), liftOutcome(_))))
private def liftOutcome[A](oc: Outcome[F, E, Option[A]]): Outcome[OptionT[F, *], E, A] =
oc match {
case Outcome.Canceled() => Outcome.Canceled()
case Outcome.Errored(e) => Outcome.Errored(e)
case Outcome.Succeeded(foa) => Outcome.Succeeded(OptionT(foa))
}
private def liftFiber[A](fib: Fiber[F, E, Option[A]]): Fiber[OptionT[F, *], E, A] =
new Fiber[OptionT[F, *], E, A] {
def cancel: OptionT[F, Unit] = OptionT.liftF(fib.cancel)
def join: OptionT[F, Outcome[OptionT[F, *], E, A]] =
OptionT.liftF(fib.join.map(liftOutcome))
}
}
private[kernel] trait EitherTGenSpawn[F[_], E0, E]
extends GenSpawn[EitherT[F, E0, *], E]
with EitherTMonadCancel[F, E0, E] {
implicit protected def F: GenSpawn[F, E]
def unique: EitherT[F, E0, Unique.Token] =
EitherT.liftF(F.unique)
def start[A](fa: EitherT[F, E0, A]): EitherT[F, E0, Fiber[EitherT[F, E0, *], E, A]] =
EitherT.liftF(F.start(fa.value).map(liftFiber))
def never[A]: EitherT[F, E0, A] = EitherT.liftF(F.never)
def cede: EitherT[F, E0, Unit] = EitherT.liftF(F.cede)
def racePair[A, B](fa: EitherT[F, E0, A], fb: EitherT[F, E0, B]): EitherT[
F,
E0,
Either[
(Outcome[EitherT[F, E0, *], E, A], Fiber[EitherT[F, E0, *], E, B]),
(Fiber[EitherT[F, E0, *], E, A], Outcome[EitherT[F, E0, *], E, B])]] = {
EitherT.liftF(F.uncancelable(poll =>
poll(F.racePair(fa.value, fb.value)).map {
case Left((oc, fib)) => Left((liftOutcome(oc), liftFiber(fib)))
case Right((fib, oc)) => Right((liftFiber(fib), liftOutcome(oc)))
}))
}
override def race[A, B](
fa: EitherT[F, E0, A],
fb: EitherT[F, E0, B]): EitherT[F, E0, Either[A, B]] =
EitherT(F.race(fa.value, fb.value).map(_.bisequence))
override def both[A, B](
fa: EitherT[F, E0, A],
fb: EitherT[F, E0, B]): EitherT[F, E0, (A, B)] =
EitherT(F.both(fa.value, fb.value).map(_.tupled))
override def raceOutcome[A, B](fa: EitherT[F, E0, A], fb: EitherT[F, E0, B]): EitherT[
F,
E0,
Either[Outcome[EitherT[F, E0, *], E, A], Outcome[EitherT[F, E0, *], E, B]]] =
EitherT.liftF(
F.raceOutcome(fa.value, fb.value).map(_.bimap(liftOutcome(_), liftOutcome(_))))
override def bothOutcome[A, B](fa: EitherT[F, E0, A], fb: EitherT[F, E0, B])
: EitherT[F, E0, (Outcome[EitherT[F, E0, *], E, A], Outcome[EitherT[F, E0, *], E, B])] =
EitherT.liftF(
F.bothOutcome(fa.value, fb.value).map(_.bimap(liftOutcome(_), liftOutcome(_))))
private def liftOutcome[A](
oc: Outcome[F, E, Either[E0, A]]): Outcome[EitherT[F, E0, *], E, A] =
oc match {
case Outcome.Canceled() => Outcome.Canceled()
case Outcome.Errored(e) => Outcome.Errored(e)
case Outcome.Succeeded(foa) => Outcome.Succeeded(EitherT(foa))
}
private def liftFiber[A](fib: Fiber[F, E, Either[E0, A]]): Fiber[EitherT[F, E0, *], E, A] =
new Fiber[EitherT[F, E0, *], E, A] {
def cancel: EitherT[F, E0, Unit] = EitherT.liftF(fib.cancel)
def join: EitherT[F, E0, Outcome[EitherT[F, E0, *], E, A]] =
EitherT.liftF(fib.join.map(liftOutcome))
}
}
private[kernel] trait IorTGenSpawn[F[_], L, E]
extends GenSpawn[IorT[F, L, *], E]
with IorTMonadCancel[F, L, E] {
implicit protected def F: GenSpawn[F, E]
implicit protected def L: Semigroup[L]
def unique: IorT[F, L, Unique.Token] =
IorT.liftF(F.unique)
def start[A](fa: IorT[F, L, A]): IorT[F, L, Fiber[IorT[F, L, *], E, A]] =
IorT.liftF(F.start(fa.value).map(liftFiber))
def never[A]: IorT[F, L, A] = IorT.liftF(F.never)
def cede: IorT[F, L, Unit] = IorT.liftF(F.cede)
def racePair[A, B](fa: IorT[F, L, A], fb: IorT[F, L, B]): IorT[
F,
L,
Either[
(Outcome[IorT[F, L, *], E, A], Fiber[IorT[F, L, *], E, B]),
(Fiber[IorT[F, L, *], E, A], Outcome[IorT[F, L, *], E, B])]] = {
IorT.liftF(F.uncancelable(poll =>
poll(F.racePair(fa.value, fb.value)).map {
case Left((oc, fib)) => Left((liftOutcome(oc), liftFiber(fib)))
case Right((fib, oc)) => Right((liftFiber(fib), liftOutcome(oc)))
}))
}
override def race[A, B](fa: IorT[F, L, A], fb: IorT[F, L, B]): IorT[F, L, Either[A, B]] =
IorT(F.race(fa.value, fb.value).map(_.bisequence))
override def both[A, B](fa: IorT[F, L, A], fb: IorT[F, L, B]): IorT[F, L, (A, B)] =
IorT(F.both(fa.value, fb.value).map(_.tupled))
override def raceOutcome[A, B](fa: IorT[F, L, A], fb: IorT[F, L, B])
: IorT[F, L, Either[Outcome[IorT[F, L, *], E, A], Outcome[IorT[F, L, *], E, B]]] =
IorT.liftF(F.raceOutcome(fa.value, fb.value).map(_.bimap(liftOutcome(_), liftOutcome(_))))
override def bothOutcome[A, B](fa: IorT[F, L, A], fb: IorT[F, L, B])
: IorT[F, L, (Outcome[IorT[F, L, *], E, A], Outcome[IorT[F, L, *], E, B])] =
IorT.liftF(F.bothOutcome(fa.value, fb.value).map(_.bimap(liftOutcome(_), liftOutcome(_))))
private def liftOutcome[A](oc: Outcome[F, E, Ior[L, A]]): Outcome[IorT[F, L, *], E, A] =
oc match {
case Outcome.Canceled() => Outcome.Canceled()
case Outcome.Errored(e) => Outcome.Errored(e)
case Outcome.Succeeded(foa) => Outcome.Succeeded(IorT(foa))
}
private def liftFiber[A](fib: Fiber[F, E, Ior[L, A]]): Fiber[IorT[F, L, *], E, A] =
new Fiber[IorT[F, L, *], E, A] {
def cancel: IorT[F, L, Unit] = IorT.liftF(fib.cancel)
def join: IorT[F, L, Outcome[IorT[F, L, *], E, A]] =
IorT.liftF(fib.join.map(liftOutcome))
}
}
private[kernel] trait KleisliGenSpawn[F[_], R, E]
extends GenSpawn[Kleisli[F, R, *], E]
with KleisliMonadCancel[F, R, E] {
implicit protected def F: GenSpawn[F, E]
def unique: Kleisli[F, R, Unique.Token] =
Kleisli.liftF(F.unique)
def start[A](fa: Kleisli[F, R, A]): Kleisli[F, R, Fiber[Kleisli[F, R, *], E, A]] =
Kleisli { r => F.start(fa.run(r)).map(liftFiber) }
def never[A]: Kleisli[F, R, A] = Kleisli.liftF(F.never)
def cede: Kleisli[F, R, Unit] = Kleisli.liftF(F.cede)
def racePair[A, B](fa: Kleisli[F, R, A], fb: Kleisli[F, R, B]): Kleisli[
F,
R,
Either[
(Outcome[Kleisli[F, R, *], E, A], Fiber[Kleisli[F, R, *], E, B]),
(Fiber[Kleisli[F, R, *], E, A], Outcome[Kleisli[F, R, *], E, B])]] = {
Kleisli { r =>
F.uncancelable(poll =>
poll(F.racePair(fa.run(r), fb.run(r)).map {
case Left((oc, fib)) => Left((liftOutcome(oc), liftFiber(fib)))
case Right((fib, oc)) => Right((liftFiber(fib), liftOutcome(oc)))
}))
}
}
override def race[A, B](
fa: Kleisli[F, R, A],
fb: Kleisli[F, R, B]): Kleisli[F, R, Either[A, B]] =
Kleisli { r => F.race(fa.run(r), fb.run(r)) }
override def both[A, B](fa: Kleisli[F, R, A], fb: Kleisli[F, R, B]): Kleisli[F, R, (A, B)] =
Kleisli { r => F.both(fa.run(r), fb.run(r)) }
override def raceOutcome[A, B](fa: Kleisli[F, R, A], fb: Kleisli[F, R, B]): Kleisli[
F,
R,
Either[Outcome[Kleisli[F, R, *], E, A], Outcome[Kleisli[F, R, *], E, B]]] =
Kleisli { r =>
F.raceOutcome(fa.run(r), fb.run(r)).map(_.bimap(liftOutcome(_), liftOutcome(_)))
}
override def bothOutcome[A, B](fa: Kleisli[F, R, A], fb: Kleisli[F, R, B])
: Kleisli[F, R, (Outcome[Kleisli[F, R, *], E, A], Outcome[Kleisli[F, R, *], E, B])] =
Kleisli { r =>
F.bothOutcome(fa.run(r), fb.run(r)).map(_.bimap(liftOutcome(_), liftOutcome(_)))
}
private def liftOutcome[A](oc: Outcome[F, E, A]): Outcome[Kleisli[F, R, *], E, A] = {
val nat: F ~> Kleisli[F, R, *] = new ~>[F, Kleisli[F, R, *]] {
def apply[B](fa: F[B]) = Kleisli.liftF(fa)
}
oc.mapK(nat)
}
private def liftFiber[A](fib: Fiber[F, E, A]): Fiber[Kleisli[F, R, *], E, A] =
new Fiber[Kleisli[F, R, *], E, A] {
def cancel: Kleisli[F, R, Unit] = Kleisli.liftF(fib.cancel)
def join: Kleisli[F, R, Outcome[Kleisli[F, R, *], E, A]] =
Kleisli.liftF(fib.join.map(liftOutcome))
}
}
private[kernel] trait WriterTGenSpawn[F[_], L, E]
extends GenSpawn[WriterT[F, L, *], E]
with WriterTMonadCancel[F, L, E] {
implicit protected def F: GenSpawn[F, E]
implicit protected def L: Monoid[L]
def unique: WriterT[F, L, Unique.Token] =
WriterT.liftF(F.unique)
def start[A](fa: WriterT[F, L, A]): WriterT[F, L, Fiber[WriterT[F, L, *], E, A]] =
WriterT.liftF(F.start(fa.run).map(liftFiber))
def never[A]: WriterT[F, L, A] = WriterT.liftF(F.never)
def cede: WriterT[F, L, Unit] = WriterT.liftF(F.cede)
def racePair[A, B](fa: WriterT[F, L, A], fb: WriterT[F, L, B]): WriterT[
F,
L,
Either[
(Outcome[WriterT[F, L, *], E, A], Fiber[WriterT[F, L, *], E, B]),
(Fiber[WriterT[F, L, *], E, A], Outcome[WriterT[F, L, *], E, B])]] = {
WriterT.liftF(F.uncancelable(poll =>
poll(F.racePair(fa.run, fb.run)).map {
case Left((oc, fib)) => Left((liftOutcome(oc), liftFiber(fib)))
case Right((fib, oc)) => Right((liftFiber(fib), liftOutcome(oc)))
}))
}
override def race[A, B](
fa: WriterT[F, L, A],
fb: WriterT[F, L, B]): WriterT[F, L, Either[A, B]] =
WriterT(F.race(fa.run, fb.run).map(_.bisequence))
override def both[A, B](fa: WriterT[F, L, A], fb: WriterT[F, L, B]): WriterT[F, L, (A, B)] =
WriterT(F.both(fa.run, fb.run).map { case ((l1, a), (l2, b)) => (l1 |+| l2) -> (a -> b) })
override def raceOutcome[A, B](fa: WriterT[F, L, A], fb: WriterT[F, L, B]): WriterT[
F,
L,
Either[Outcome[WriterT[F, L, *], E, A], Outcome[WriterT[F, L, *], E, B]]] =
WriterT.liftF(F.raceOutcome(fa.run, fb.run).map(_.bimap(liftOutcome(_), liftOutcome(_))))
override def bothOutcome[A, B](fa: WriterT[F, L, A], fb: WriterT[F, L, B])
: WriterT[F, L, (Outcome[WriterT[F, L, *], E, A], Outcome[WriterT[F, L, *], E, B])] =
WriterT.liftF(F.bothOutcome(fa.run, fb.run).map(_.bimap(liftOutcome(_), liftOutcome(_))))
private def liftOutcome[A](oc: Outcome[F, E, (L, A)]): Outcome[WriterT[F, L, *], E, A] =
oc match {
case Outcome.Canceled() => Outcome.Canceled()
case Outcome.Errored(e) => Outcome.Errored(e)
case Outcome.Succeeded(foa) => Outcome.Succeeded(WriterT(foa))
}
private def liftFiber[A](fib: Fiber[F, E, (L, A)]): Fiber[WriterT[F, L, *], E, A] =
new Fiber[WriterT[F, L, *], E, A] {
def cancel: WriterT[F, L, Unit] = WriterT.liftF(fib.cancel)
def join: WriterT[F, L, Outcome[WriterT[F, L, *], E, A]] =
WriterT.liftF(fib.join.map(liftOutcome))
}
}
}