Future.firstSuccessfulOf

firstSuccessfulOf.scala

import scala.concurrent._
import scala.util.{Success, Failure}
import scala.collection.immutable.Seq

// Returns first successful future result, or last failure if all futures failed
def firstSuccessfulOf[A](futures: Seq[Future[A]])(implicit executor: ExecutionContext): Future[A] = {
  val total = futures.length
  val counter = new java.util.concurrent.atomic.AtomicInteger(total)
  val p = Promise[A]()

  futures.foreach { fut =>
    fut.onComplete {
      case Success(a) => p.trySuccess(a)
      case Failure(failure) =>
        if (counter.decrementAndGet() == 0) p.failure(failure)
    }
  }

  p.future
}