首先是什么有效：（我的问题的描述进一步向下）
客户端应用程序向服务器 WebAPI 发送长数据流。请求被分块（request.Headers.TransferEncodingChunked = True），数据“即时”写入流。
数据由序列化对象组成，每个对象代表自定义类Chunk。
一切正常，服务器可以在客户端完成写入之前开始读取流（控制器禁用服务器输入缓冲）。
开始请求：
Public Async Function Transfer(authCookie As Cookie) As Task
Using handler As New HttpClientHandler()
handler.CookieContainer = New Net.CookieContainer
handler.CookieContainer.Add(authCookie)
'Client instance
Using client As New HttpClient(handler), content As New Content(AddressOf WriteToStream)
'Send stream asynchronously
Dim request As New HttpRequestMessage(HttpMethod.Post, "https://myserver.net/api/datastream")
request.Content = content
request.Headers.TransferEncodingChunked = True
Await client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead).ContinueWith(
Async Function(requestTask)
Dim response As HttpResponseMessage = Nothing
Try
response = Await requestTask
Catch ex As Exception
'Exception writing the stream
Exit Function
End Try
Try
response.EnsureSuccessStatusCode()
Catch ex As Exception
'Exception on server ocurred
End Try
response.RequestMessage.Dispose()
response.Dispose()
End Function)
End Using
End Using
End Function
Public Sub WriteToStream(str As IO.Stream)
'Head-chunk
head.attachedChunks.CompleteAdding()
'Write head-chunk to stream
Task.Run(
Async Function()
Await head.WriteToStream(str)
End Function).Wait()
End Sub
HttpContent 类：
Public Class Content
Inherits Net.Http.HttpContent
Protected ReadOnly actionOfStream As Action(Of IO.Stream)
Public Sub New(action As Action(Of IO.Stream))
If action Is Nothing Then Throw New ArgumentNullException("action")
actionOfStream = action
End Sub
Protected Overrides Function SerializeToStreamAsync(stream As IO.Stream, context As Net.TransportContext) As Task
Return Task.Factory.StartNew(
Sub(obj)
Dim target As IO.Stream = DirectCast(obj, IO.Stream)
actionOfStream(target)
End Sub,
stream)
End Function
Protected Overrides Function TryComputeLength(ByRef length As Long) As Boolean
length = -1
Return False
End Function
End Class
该方法WriteToStream()调用 Head-chunks WriteToStream()，它为其子块调用相同的方法：
Public Class Chunk
'More properties here
Public Property attachedChunks As BlockingCollection(Of Chunk)
Public Overridable Async Function WriteToStream(str As IO.Stream) As Task
Using serializationStream As New IO.MemoryStream
'Serialize
Serializer.Serialize(Of Chunk)(serializationStream, Me)
'Write length
Dim cnt As Integer = CInt(serializationStream.Length)
Dim cntBuffer() As Byte = BitConverter.GetBytes(cnt)
Await str.WriteAsync(cntBuffer, 0, cntBuffer.Length)
'Write chunk
serializationStream.Seek(0, IO.SeekOrigin.Begin)
Await serializationStream.CopyToAsync(str)
End Using
Await str.FlushAsync()
'Clearing and disposing stuff
'...
'Write sub-chunks
If attachedChunks IsNot Nothing Then
For Each chunk As Chunk In attachedChunks.GetConsumingEnumerable
Await chunk.WriteToStream(str)
Next
attachedChunks.Dispose()
End If
'Write ending mark
If attachedChunksIndefiniteCount Then
Await str.WriteAsync({0, 0, 0, 0}, 0, 4)
End If
End Function
End Class
到目前为止，一切都很好。
当我开始使用像 GZipStream 这样的压缩来压缩我的 Chunk 时，问题就来了：请求在客户端被缓冲，所以它接缝。
这是-class的WriteToStream()方法：Chunk
Public Class Chunk
'More properties here
Public Property attachedChunks As BlockingCollection(Of Chunk)
Public Overridable Async Function WriteToStream(str As IO.Stream) As Task
Using serializationStream As New IO.MemoryStream
'Serialization and compression
Using gZipStream As New IO.Compression.GZipStream(serializationStream, IO.Compression.CompressionMode.Compress, True)
Using bufferStream As New IO.BufferedStream(gZipStream, 64 * 1024)
'Serialize
Serializer.Serialize(Of Chunk)(bufferStream, Me)
End Using
End Using
'Write length
Dim cnt As Integer = CInt(serializationStream.Length)
Dim cntBuffer() As Byte = BitConverter.GetBytes(cnt)
Await str.WriteAsync(cntBuffer, 0, cntBuffer.Length)
'Write chunk
serializationStream.Seek(0, IO.SeekOrigin.Begin)
Await serializationStream.CopyToAsync(str)
End Using
Await str.FlushAsync()
'Clearing and disposing stuff
'...
'Write sub-chunks
If attachedChunks IsNot Nothing Then
For Each chunk As Chunk In attachedChunks.GetConsumingEnumerable
Await chunk.WriteToStream(str)
Next
attachedChunks.Dispose()
End If
'Write ending mark
If attachedChunksIndefiniteCount Then
Await str.WriteAsync({0, 0, 0, 0}, 0, 4)
End If
End Function
End Class
在写入所有数据之前，它不会发送请求。请求是否缓冲流？GZipStream 对某种底层上下文有影响吗？我无法弄清楚问题是什么......