Scala: Combining a list of Future for all successes and errors

Question

I have a list of Future, with each Future completing with a List of values OR with a failure. I am trying to combine these futures in a way that all available values are captured and errors are logged. This is my attempt:

val individualFutures:  List[Future[Seq[Element]]] = ....
val allElements: Future[List[Element]] = Future.foldLeft(individualFutures)(List[Element]())((acc, 
     elements) => acc ++ elements)
Try(Await.result(allElements, Duration.Inf)) match {
      case Success(elements) => ....
      case Failure(error)    => ....log
}

But I don't think this is right way to achieve my objective. I guess as soon as a future completes with an error, this would stop there.

How can I achieve same?

Answer 1

Maybe you could traverse the list and recover from throwables by returning an empty list and logging a failure reason? At the end you would flatten the whole sequence.

  val allElements: Future[List[Element]] = Future.traverse(individualFutures) {
    _.recover {
      case throwable: Throwable =>
        println(throwable.getMessage)
        Nil
    }
  }.map(_.flatten)