如何在 Scala 中为未来添加截止日期？-解网

问：

假设我有一个函数，并希望它返回一个在截止日期之前完成的新未来。所以我正在编写一个这样的新函数fab: A => Future[B]deadlined

def deadlined[B](fut: => Future[B], deadline: Deadline): Future[B] = ???

现在我正在使用，但可以按照建议使用。不过，最好的解决方案可能是将调度实现抽象出来，并按照注释中的建议在测试中模拟它。java.util.TimerScheduledThreadPoolExecutor

object Deadlined {

  private val timer = new java.util.Timer() // todo: replace it with a wrapper

  def apply[B](fut: => Future[B], deadline: Deadline)(implicit ec: ExecutionContext): Future[B] = {
    val promise = Promise[B]()
    val timerTask = new java.util.TimerTask {
      override def run(): Unit = promise.failure(new Exception(s"$deadline is exceeded"))
    }
    timer.schedule(timerTask, deadline.timeLeft.toMillis)
    fut.transform { result =>
      timerTask.cancel()
      result match {
        case Success(b) => promise.success(b)
        case Failure(t) => promise.failure(t)
      }
      result
    }
    promise.future
  }
}

这有意义吗？我还想知道如何从对我上一个问题的回答中剔除一个共同的部分和延迟。Deadlined

Scala 未来的截止日期

import scala.concurrent.{Future, ExecutionContext}
import scala.concurrent.duration.FiniteDuration
import java.util.{Timer, TimerTask}

implicit class DeadlineFuture[T](future: Future[T]) {
  def deadline(d: FiniteDuration)(implicit timer: Timer): Future[T] = {
    if (future.isCompleted) future
    else {
      val promise = Promise[T]()
      val timerTask = new TimerTask {
        override def run(): Unit = promise.tryFailure(new Exception(s"$d is exceeded"))
      }
      timer.schedule(timerTask, d.toMillis)
      future.onComplete(_ => timerTask.cancel())(ExecutionContext.parasitic)
      promise.completeWith(future).future
    }
  }
}

// Usage:
Future.never.deadline(5.seconds).onComplete(println)

如何在 Scala 中为未来添加截止日期？

How to add a deadline to a future in Scala?

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