8

我正在尝试将基于 akka 流的流集成到我的 Play 2.5 应用程序中。这个想法是您可以流式传输照片，然后将其作为原始文件、缩略图版本和水印版本写入磁盘。

我设法使用类似这样的图表来完成这项工作：

val byteAccumulator = Flow[ByteString].fold(new ByteStringBuilder())((builder, b) => {builder ++= b.toArray})
                                    .map(_.result().toArray)

def toByteArray = Flow[ByteString].map(b => b.toArray)

val graph = Flow.fromGraph(GraphDSL.create() {implicit builder =>
  import GraphDSL.Implicits._
  val streamFan = builder.add(Broadcast[ByteString](3))
  val byteArrayFan = builder.add(Broadcast[Array[Byte]](2))
  val output = builder.add(Flow[ByteString].map(x => Success(Done)))

  val rawFileSink = FileIO.toFile(file)
  val thumbnailFileSink = FileIO.toFile(getFile(path, Thumbnail))
  val watermarkedFileSink = FileIO.toFile(getFile(path, Watermarked))

  streamFan.out(0) ~> rawFileSink
  streamFan.out(1) ~> byteAccumulator ~> byteArrayFan.in
  streamFan.out(2) ~> output.in

  byteArrayFan.out(0) ~> slowThumbnailProcessing ~> thumbnailFileSink
  byteArrayFan.out(1) ~> slowWatermarkProcessing ~> watermarkedFileSink

  FlowShape(streamFan.in, output.out)
})

graph

}

然后我使用这样的累加器将它连接到我的播放控制器：

val sink = Sink.head[Try[Done]]

val photoStorageParser = BodyParser { req =>
     Accumulator(sink).through(graph).map(Right.apply)
}

问题是我的两个处理过的文件接收器没有完成，两个处理过的文件的大小都为零，但不是原始文件。我的理论是累加器只等待我的扇出的一个输出，所以当输入流完成并且我的 byteAccumulator 吐出完整的文件时，到处理完成时，播放已经从输出中获得了物化值.

所以，我的问题是：
就我的方法而言，我是否走在正确的轨道上？运行这样的图表的预期行为是什么？我怎样才能把我所有的水槽放在一起形成一个最终的水槽？

4

1 回答 1

8

好的，经过一点帮助（安德烈亚斯在正确的轨道上），我已经找到了这个解决方案：

val rawFileSink = FileIO.toFile(file)
val thumbnailFileSink = FileIO.toFile(getFile(path, Thumbnail))
val watermarkedFileSink = FileIO.toFile(getFile(path, Watermarked))

val graph = Sink.fromGraph(GraphDSL.create(rawFileSink, thumbnailFileSink, watermarkedFileSink)((_, _, _)) {
  implicit builder => (rawSink, thumbSink, waterSink) => {
    val streamFan = builder.add(Broadcast[ByteString](2))
    val byteArrayFan = builder.add(Broadcast[Array[Byte]](2))

    streamFan.out(0) ~> rawSink
    streamFan.out(1) ~> byteAccumulator ~> byteArrayFan.in

    byteArrayFan.out(0) ~> processorFlow(Thumbnail) ~> thumbSink
    byteArrayFan.out(1) ~> processorFlow(Watermarked) ~> waterSink

    SinkShape(streamFan.in)
  }
})

graph.mapMaterializedValue[Future[Try[Done]]](fs => Future.sequence(Seq(fs._1, fs._2, fs._3)).map(f => Success(Done)))

之后很容易从 Play 调用它：

val photoStorageParser = BodyParser { req =>
  Accumulator(theSink).map(Right.apply)
}

def createImage(path: String) = Action(photoStorageParser) { req =>
  Created
}
于 2016-05-10T17:14:11.097 回答