内存不够的异常使用的HttpWebRequest当到流大文件 [英] Out of Memory Exception When Using HttpWebRequest to Stream Large File

问题描述

我用一个大文件的Http.Put时得到一个内存溢出异常。我使用异步模型中所示的代码。我想数据的8K块发送到Windows 2008 R2服务器。当我尝试写超过536868864字节的数据块的异常持续发生。在下面的代码片段代码中的requestStream.Write方法发生异常。

寻找原因？

请注意：较小的文件都将确定。如果我写一个本地的FileStream逻辑也适用。在Win 7旗舰版客户端的计算机上运行VS 2010，.NET 4.0。

  HttpWebRequest的要求=（HttpWebRequest的）WebRequest.Create（宀：//网站/文件服务器/文件名）; 
 request.Method = WebRequestMethods.Http.Put; 
 request.SendChunked = TRUE; 
 request.AllowWriteStreamBuffering = TRUE; 
 ... 
 
 request.BeginGetRequestStream（新的AsyncCallback（EndGetStreamCallback），状态）; 
 ... 
 
 INT块= 8192; //其它值给出相同的结果
 .... 
 
私有静态无效EndGetStreamCallback（IAsyncResult的AR）{
长限制= 0; 
长文件长度; 
的HttpState状态=（的HttpState）ar.AsyncState; 
 
流requestStream = NULL; 
 //结束异步调用获得请求的流。 
 
尝试{
 requestStream = state.Request.EndGetRequestStream（AR）; 
 //文件内容复制到请求流。 
 
的FileStream流=新的FileStream（state.FileName，FileMode.Open，FileAccess.Read，FileShare.None，块，FileOptions.SequentialScan）; 
 
 BinaryReader binReader =新BinaryReader（流）; 
 =文件长度stream.Length; 
 
 //设置位置到流的开头。 
 binReader.BaseStream.Position = 0; 
 
字节[] = fileContents新的字节[块] 
 
 //从缓冲区
读取文件时（限<文件长度）
 {
 fileContents = binReader.ReadBytes（块）; 
 
 //下面两行尝试写入网络和服务器
 requestStream.Write（fileContents，0，块）; //导致内存耗尽之后536868864字节
 requestStream.Flush（）; //我得到有或没有冲洗
 
 +限块=相同的结果; 
} 
 
 //重要提示：在发送请求之前关闭请求流。 
 stream.Close（）; 
 
 requestStream.Close（）; 
} 
} 
  

解决方案

您显然有这个记录问题。当 AllowWriteStreamBuffering 是真正，它缓冲的所有数据写入请求的！因此，解是该属性设置为假：

要解决此问题，将HttpWebRequest.AllowWriteStreamBuffering属性设置为false。

I get an Out of Memory Exception when using Http.Put of a large file. I am using an asynchronous model as shown in the code. I am trying to send 8K blocks of data to a Windows 2008 R2 server. The exception consistently occurs when I attempt to write a block of data that exceeds 536,868,864 bytes. The exception occurs on the requestStream.Write method in the code snippet below.

Looking for reasons why?

Note: Smaller files are PUT OK. Logic also works if I write to a local FileStream. Running VS 2010, .Net 4.0 on Win 7 Ultimate client computer.

   HttpWebRequest request = (HttpWebRequest)WebRequest.Create("Http://website/FileServer/filename");
   request.Method = WebRequestMethods.Http.Put;
   request.SendChunked = true;
   request.AllowWriteStreamBuffering = true;
   ...

   request.BeginGetRequestStream( new AsyncCallback(EndGetStreamCallback), state);
   ...

   int chunk = 8192; // other values give same result
   ....

   private static void EndGetStreamCallback(IAsyncResult ar) {
        long limit = 0;
        long fileLength;
        HttpState state = (HttpState)ar.AsyncState;

        Stream requestStream = null;
        // End the asynchronous call to get the request stream.

        try {
            requestStream = state.Request.EndGetRequestStream(ar);
            // Copy the file contents to the request stream.

            FileStream stream = new FileStream(state.FileName, FileMode.Open, FileAccess.Read, FileShare.None, chunk, FileOptions.SequentialScan);

            BinaryReader binReader = new BinaryReader(stream);
            fileLength = stream.Length;

            // Set Position to the beginning of the stream.
            binReader.BaseStream.Position = 0;

            byte[] fileContents = new byte[chunk];

            // Read File from Buffer 
            while (limit < fileLength)
            {
                fileContents = binReader.ReadBytes(chunk);

                // the next 2 lines attempt to write to network and server
                requestStream.Write(fileContents, 0, chunk);   // causes Out of memory after 536,868,864 bytes
                requestStream.Flush();  // I get same result with or without Flush

                limit += chunk;
            }

            // IMPORTANT: Close the request stream before sending the request.
            stream.Close();

            requestStream.Close();
        }
    }

解决方案

You apparently have this documented problem. When AllowWriteStreamBuffering is true, it buffers all the data written to the request! So, the "solution" is to set that property to false:

To work around this issue, set the HttpWebRequest.AllowWriteStreamBuffering property to false.

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