我正在Scala中构建一个Play Framework应用程序,我想将一个字节数组流式传输到S3.我正在使用Play-S3库来执行此操作.文档部分的"Multipart文件上传"与此处相关:
// Retrieve an upload ticket val result:Future[BucketFileUploadTicket] = bucket initiateMultipartUpload BucketFile(fileName, mimeType) // Upload the parts and save the tickets val result:Future[BucketFilePartUploadTicket] = bucket uploadPart (uploadTicket, BucketFilePart(partNumber, content)) // Complete the upload using both the upload ticket and the part upload tickets val result:Future[Unit] = bucket completeMultipartUpload (uploadTicket, partUploadTickets)
我试图在我的应用程序中做同样的事情,但用Iteratee
s和Enumerator
s.
流和异步性使事情变得有点复杂,但这是我到目前为止(注意uploadTicket
在代码的前面定义):
val partNumberStream = Stream.iterate(1)(_ + 1).iterator val partUploadTicketsIteratee = Iteratee.fold[Array[Byte], Future[Vector[BucketFilePartUploadTicket]]](Future.successful(Vector.empty[BucketFilePartUploadTicket])) { (partUploadTickets, bytes) => bucket.uploadPart(uploadTicket, BucketFilePart(partNumberStream.next(), bytes)).flatMap(partUploadTicket => partUploadTickets.map( _ :+ partUploadTicket)) } (body |>>> partUploadTicketsIteratee).andThen { case result => result.map(_.map(partUploadTickets => bucket.completeMultipartUpload(uploadTicket, partUploadTickets))) match { case Success(x) => x.map(d => println("Success")) case Failure(t) => throw t } }
一切都编译和运行没有事故.事实上,"Success"
得到打印,但没有文件出现在S3上.
您的代码可能存在多个问题.由map
方法调用引起的有点不可读.您的未来构图可能有问题.另一个问题可能是由于所有块(除了最后一块)至少应为5MB.
下面的代码尚未经过测试,但显示了不同的方法.iteratee方法是一种可以创建小构建块并将它们组合成一个操作管道的方法.
为了使代码编译,我添加了一个特征和一些方法
trait BucketFilePartUploadTicket val uploadPart: (Int, Array[Byte]) => Future[BucketFilePartUploadTicket] = ??? val completeUpload: Seq[BucketFilePartUploadTicket] => Future[Unit] = ??? val body: Enumerator[Array[Byte]] = ???
这里我们创建几个部分
// Create 5MB chunks val chunked = { val take5MB = Traversable.takeUpTo[Array[Byte]](1024 * 1024 * 5) Enumeratee.grouped(take5MB transform Iteratee.consume()) } // Add a counter, used as part number later on val zipWithIndex = Enumeratee.scanLeft[Array[Byte]](0 -> Array.empty[Byte]) { case ((counter, _), bytes) => (counter + 1) -> bytes } // Map the (Int, Array[Byte]) tuple to a BucketFilePartUploadTicket val uploadPartTickets = Enumeratee.mapM[(Int, Array[Byte])](uploadPart.tupled) // Construct the pipe to connect to the enumerator // the ><> operator is an alias for compose, it is more intuitive because of // it's arrow like structure val pipe = chunked ><> zipWithIndex ><> uploadPartTickets // Create a consumer that ends by finishing the upload val consumeAndComplete = Iteratee.getChunks[BucketFilePartUploadTicket] mapM completeUpload
只需连接部件即可完成运行
// This is the result, a Future[Unit] val result = body through pipe run consumeAndComplete
请注意,我没有测试任何代码,可能在我的方法中犯了一些错误.然而,这显示了处理问题的不同方式,并且应该可以帮助您找到一个好的解决方案.
请注意,此方法在进入下一部分之前等待一部分完成上载.如果从服务器到亚马逊的连接比从浏览器到服务器的连接慢,则此机制将减慢输入.
你可以采取另一种方法,你不要等待Future
零件上传完成.这将导致您使用另一个步骤Future.sequence
将上传期货序列转换为包含结果序列的单个未来.结果将是一旦有足够的数据就将一个部件发送到亚马逊的机制.