Akka Source 不流数据？

Question

val pageDataFutures : Seq[Future[PageData]]= ??? //4 api calls each resulting in a future of PageData

  def source : Source[PageData, NotUsed] = Source(
    pageDataFutures.flatMap(future => Await.result(future,atMost)).toList
  )

  source.runForeach(println)

我希望在每个 future 完成时运行 'runForEach' 来源。但是所有 4 api 调用都被调用，然后源中的数据被一次打印出来。它不应该打印可用的数据吗？我为每个未来使用 Await。因此可以保证在下一个 future Awaited 之前，前一个 future 的结果可用并且可以被 println

使用

Answer 1

使用mapAsync:

Pass incoming elements to a function that return a Future result. When the Future arrives the result is passed downstream. Up to n elements can be processed concurrently, but regardless of their completion time the incoming order will be kept when results complete.

val pageDataFutures: Seq[Future[PageData]] = ???

Source(pageDataFutures)
  .mapAsync(parallelism = 1)(x => x) // or: mapAsync(parallelism = 1)(identity)
  .runForeach(println)

Akka Source 不流数据？

Akka Source not streaming data?

scala

akka

akka-stream