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Interrupt tasks on failure in ZStream#mapMPar #3881

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Merged
merged 1 commit into from
Jun 26, 2020
Merged

Interrupt tasks on failure in ZStream#mapMPar #3881

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15 changes: 14 additions & 1 deletion streams-tests/shared/src/test/scala/zio/stream/ZStreamSpec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1963,7 +1963,20 @@ object ZStreamSpec extends ZIOBaseSpec {
.run
.map(_.interrupted)
)(equalTo(false))
} @@ nonFlaky(10)
} @@ nonFlaky(10),
testM("interrupts pending tasks when one of the tasks fails") {
for {
interrupted <- Ref.make(0)
latch1 <- Promise.make[Nothing, Unit]
latch2 <- Promise.make[Nothing, Unit]
_ <- ZStream(
latch1.succeed(()) *> ZIO.never.onInterrupt(interrupted.update(_ + 1)),
latch2.succeed(()) *> ZIO.never.onInterrupt(interrupted.update(_ + 1)),
latch1.await *> latch2.await *> ZIO.fail("Boom")
).mapMPar(3)(identity).runDrain.run
count <- interrupted.get
} yield assert(count)(equalTo(2))
}
),
suite("mergeTerminateLeft")(
testM("terminates as soon as the first stream terminates") {
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17 changes: 12 additions & 5 deletions streams/shared/src/main/scala/zio/stream/ZStream.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1919,18 +1919,25 @@ abstract class ZStream[-R, +E, +O](val process: ZManaged[R, Nothing, ZIO[R, Opti
final def mapMPar[R1 <: R, E1 >: E, O2](n: Int)(f: O => ZIO[R1, E1, O2]): ZStream[R1, E1, O2] =
ZStream[R1, E1, O2] {
for {
out <- Queue.bounded[ZIO[R1, Option[E1], O2]](n).toManaged(_.shutdown)
permits <- Semaphore.make(n.toLong).toManaged_
out <- Queue.bounded[ZIO[R1, Option[E1], O2]](n).toManaged(_.shutdown)
errorSignal <- Promise.make[E1, Nothing].toManaged_
permits <- Semaphore.make(n.toLong).toManaged_
_ <- self.foreachManaged { a =>
for {
p <- Promise.make[E1, O2]
latch <- Promise.make[Nothing, Unit]
_ <- out.offer(p.await.mapError(Some(_)))
_ <- permits.withPermit(latch.succeed(()) *> f(a).to(p)).fork
_ <- latch.await
_ <- permits.withPermit {
latch.succeed(()) *> // Make sure we start evaluation before moving on to the next element
(errorSignal.await // Interrupt evaluation if another task fails
raceFirst f(a))
.tapCause(errorSignal.halt) // Notify other tasks of a failure
.to(p) // Transfer the result to the consuming stream
}.fork
_ <- latch.await
} yield ()
}.foldCauseM(
c => out.offer(Pull.halt(c)).unit.toManaged_,
c => out.offer(Pull.halt(c)).toManaged_,
_ => (permits.withPermits(n.toLong)(ZIO.unit).interruptible *> out.offer(Pull.end)).toManaged_
)
.fork
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