memoizeExpiring

memoizeExpiring.scala

import monix.eval._
import monix.execution.atomic.Atomic

def memoizeExpiring[A](sourceTask: Task[A], interval: FiniteDuration): Task[A] = {

  class State {

    val memoizedTask: Task[A] = sourceTask.memoize
    val deadline: Deadline = interval.fromNow
  }

  val atomic = Atomic(new State)

  @tailrec def loop(): State = {
    val current = atomic.get
    if (current.deadline.isOverdue) {
      val update = new State
      if (!atomic.compareAndSet(current, update)) loop() // retry
      else update
    } else {
      current
    }
  }

  Task.defer { loop().memoizedTask }
}