Question

我正在尝试使用akka-streams和akka-http以及alpakka库将文件下载/上传到Amazon S3。我看到两个可能相关的问题......

我只能下载非常小的文件，最大的一个8kb。
我无法上传较大的文件。它失败并显示消息

处理请求时出错：'Substream Source尚未发生在5000毫秒内实现。完成500内部服务器错误响应。要更改默认的异常处理行为，提供自定义ExceptionHandler。 akka.stream.impl.SubscriptionTimeoutException：子流源尚未在5000毫秒内实现

这是我的路线

pathEnd {
           post {
             fileUpload("attachment") {
               case (metadata, byteSource) => {
                 val writeResult: Future[MultipartUploadResult] = byteSource.runWith(client.multipartUpload("bucketname", key))
                 onSuccess(writeResult) { result =>
                   complete(result.location.toString())
                 }
               }

             }
           }

         } ~

     path("key" / Segment) {
            (sourceSystem, sourceTable, sourceId) =>
              get {
                val result: Future[ByteString] = 
         client.download("bucketname", key).runWith(Sink.head)
                onSuccess(result) {
                  complete(_)
                }
              }
          }

尝试下载100KB的文件将最终获取文件的截断版本，通常大小约为16-25Kb 任何帮助表示赞赏

编辑：对于下载问题，我接受了Stefano的建议并获得了

[error]  found   : akka.stream.scaladsl.Source[akka.util.ByteString,akka.NotUsed]
[error]  required: akka.http.scaladsl.marshalling.ToResponseMarshallable

这使它起作用

complete(HttpEntity(ContentTypes.`application/octet-stream`, client.download("bucketname", key).runWith(Sink.head)))

Answer 1

1）关于下载问题：通过调用

val result: Future[ByteString] = 
         client.download("bucketname", key).runWith(Sink.head)

您将所有数据从S3流式传输到内存中，然后提供结果。

Akka-Http作为流支持，允许您直接从源流式传输字节，而无需在内存中缓冲它们。有关这方面的更多信息，请参阅docs。实际上，这意味着complete指令可以采用Source[ByteString, _]，如

...
get {
  complete(client.download("bucketname", key))
}

2）关于上传问题：您可以尝试调整Akka HTTP akka.http.server.parsing.max-content-length设置：

# Default maximum content length which should not be exceeded by incoming request entities.
# Can be changed at runtime (to a higher or lower value) via the `HttpEntity::withSizeLimit` method.
# Note that it is not necessarily a problem to set this to a high value as all stream operations
# are always properly backpressured.
# Nevertheless you might want to apply some limit in order to prevent a single client from consuming
# an excessive amount of server resources.
#
# Set to `infinite` to completely disable entity length checks. (Even then you can still apply one
# programmatically via `withSizeLimit`.)
max-content-length = 8m

测试这个的结果代码将是：

  withoutSizeLimit {
    fileUpload("attachment") {
      ...
    }
  }

在akka-http / akka-streams中上传/下载文件时出现问题

1 个答案: