IterateeBatchProcessing.scala

  def processBatches[T](input: Enumerator[T], parallelism: Int)
                       (process: T => Future[Unit])
                       (implicit ec: ExecutionContext): Future[Unit] = {
    input.through(Enumeratee.map(process) compose chunker(parallelism)).run(Iteratee.foldM(()) {
      case (_, results) => Future.sequence(results) map (_ => ())
    })
  }

  def chunker[T](size: Int): Enumeratee[T, List[T]] =
    Enumeratee.grouped(Enumeratee.take(size).transform(Iteratee.getChunks[T]))