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An Implementation of a Safe Multi-value Race
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object RaceN { | |
import cats.implicits._ | |
import cats.effect._ | |
import cats.effect.concurrent._ | |
import cats.data.NonEmptyList | |
// Use with atleast 3, otherwise you should prefer Concurrent.race | |
def raceN[F[_]: Concurrent, A](x1: F[A], x2: F[A], x3: F[A], xs: F[A]*): F[Either[NonEmptyList[Throwable], A]] = { | |
for { | |
deferred <- Deferred[F, A] | |
out <- Bracket[F, Throwable].bracket( | |
NonEmptyList.of(x1, x2 +: x3 +: xs:_*).traverse(fa => | |
Concurrent[F].start(fa.flatMap(a => deferred.complete(a).as(a)).attempt) | |
) | |
){ | |
fibers: NonEmptyList[Fiber[F, Either[Throwable, A]]] => | |
Concurrent[F].race( | |
fibers.traverse(_.join).map( | |
_.traverse(_.swap).swap | |
), | |
deferred.get | |
) | |
}( | |
fibers => fibers.traverse_(_.cancel.attempt) | |
) | |
} yield out.fold(identity, Either.right) | |
} | |
} |
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