将大文件从 FTP 下载到 Azure Web 应用程序时出现 ASP.Net-Core WebException

问题描述

我正在尝试构建一个 Web 应用程序，该应用程序可以触发后台任务以将 .zip 文件从 FTP 下载到本地存储。

• 框架：ASP.Net-Core 3.1
• 托管：Azure 服务计划 P2V2
• 作业处理程序： Hangfire
• 源文件大小：1GB - 4GB

在本地运行时，我按预期下载文件没有问题。但是在生产中运行，如果任务运行超过 18 分钟，我会遇到以下问题：

Failed
An exception occurred during performance of the job.

System.Net.WebException
The underlying connection was closed: An unexpected error occurred on a receive

System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive
   at System.Runtime.ExceptionServices.ExceptiondispatchInfo.Throw(Exception source)
   at System.Net.FtpWebRequest.SyncRequestCallback(Object obj)
   at System.Net.CommandStream.InvokeRequestCallback(Object obj)
   at System.Net.CommandStream.Abort(Exception e)
   at System.Net.CommandStream.CheckContinuePipeline()
   at System.Net.FtpWebRequest.DataStreamClosed(CloseExState closeState)
   at System.Net.FtpDataStream.System.Net.ICloseEx.CloseEx(CloseExState closeState)
   at System.Net.FtpDataStream.dispose(Boolean disposing)
   at System.IO.Stream.Close()
   at System.Net.FtpDataStream.Read(Byte[] buffer,Int32 offset,Int32 size)
   at dataimportTool.Controllers.MyController.DownloadFile(String fileName) in D:\home\site\repository\MyProject\Controllers\MyController.cs:line 98

执行任务中使用的代码如下：

FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://address_removed" + fileName);
request.Credentials = new NetworkCredential("username","password");
request.Proxy = null;
request.UseBinary = true;
request.UsePassive = true;
request.KeepAlive = true;
request.Method = WebRequestMethods.Ftp.GetFileSize;

FtpWebResponse response = (FtpWebResponse)request.GetResponse();
long fileSize = response.ContentLength;

request = (FtpWebRequest)WebRequest.Create("ftp://address_removed" + fileName);
request.Credentials = new NetworkCredential("username","password");
request.UseBinary = true;
request.UsePassive = true;
request.KeepAlive = true;
request.Method = WebRequestMethods.Ftp.DownloadFile;

var filePath = Path.Combine(Directory.GetCurrentDirectory(),@"wwwroot\downloads",fileName);

using (FtpWebResponse responseFileDownload = (FtpWebResponse)request.GetResponse())
using (Stream responseStream = responseFileDownload.GetResponseStream())
using (FileStream writeStream = new FileStream(filePath,FileMode.Create))
{
   int Length = 2048;
   Byte[] buffer = new Byte[Length];
   int bytesRead = responseStream.Read(buffer,Length);
   long bytes = 0;

   while (bytesRead > 0)
   {
      writeStream.Write(buffer,bytesRead);
      bytesRead = responseStream.Read(buffer,Length);
      bytes += bytesRead;
   }
}

如果有人能帮助解决这个问题，我们将不胜感激。

解决方法

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