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[DO NOT MERGE] Modify file upload sample to handle very large files #33809

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@amcasey amcasey commented Oct 7, 2024

Illustration for dotnet/aspnetcore#58233.

We may want to consider updating the sample properly, but this is just a proof of concept.

@@ -24,7 +24,7 @@ public class StreamingController : Controller
private readonly AppDbContext _context;
private readonly long _fileSizeLimit;
private readonly ILogger<StreamingController> _logger;
private readonly string[] _permittedExtensions = { ".txt" };
private readonly string[] _permittedExtensions = { ".txt", ".vhdx" };
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This was just an easy format in which to make a very large file.

streamedFileContent =
await FileHelpers.ProcessStreamedFile(section, contentDisposition,
ModelState, _permittedExtensions, _fileSizeLimit);
using (var memoryStream = new MemoryStream())
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This will still blow up over ~2GB. I only fixed up the file impl, not the EF impl.


if (!ModelState.IsValid)
{
return BadRequest(ModelState);
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We should probably delete the file if this happens.

@@ -20,6 +20,12 @@ public static IHostBuilder CreateHostBuilder(string[] args) =>
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
webBuilder.ConfigureKestrel(options =>
{
options.Limits.MaxRequestBodySize = 6L << 30; // 6 GB
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This actually matters. The next two should just help perf for HTTP/2 (always measure though).

@@ -1,11 +1,11 @@
<Project Sdk="Microsoft.NET.Sdk.Web">

<PropertyGroup>
<TargetFramework>netcoreapp3.1</TargetFramework>
<TargetFramework>net9.0</TargetFramework>
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This mostly just made debugging easier. It's possible my changes work in 3.1 as well.

using (var memoryStream = new MemoryStream())
{
await section.Body.CopyToAsync(memoryStream);
await section.Body.CopyToAsync(destination);
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Reading into a MemoryStream was the real bottleneck, AFAICT>

@@ -187,9 +181,8 @@ public static async Task<byte[]> ProcessStreamedFile(
"The upload failed. Please contact the Help Desk " +
$" for support. Error: {ex.HResult}");
// Log the exception
destination.SetLength(oldLength); // Reset the stream to its original length
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This clean-up may be inadequate or even counter-productive.

@@ -208,7 +201,7 @@ private static bool IsValidFileExtensionAndSignature(string fileName, Stream dat

data.Position = 0;

using (var reader = new BinaryReader(data))
using (var reader = new BinaryReader(data, System.Text.Encoding.UTF8, leaveOpen: true))
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If we're going to operate on a real stream, we should probably not close it after validation.

@@ -247,12 +240,10 @@ private static bool IsValidFileExtensionAndSignature(string fileName, Stream dat
// for files (when possible) for all file types you intend
// to allow on the system and perform the file signature
// check.
/*
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I was too lazy to work out a file signature for VHDX for a sample.

"StoredFilesPath": "c:\\files",
"FileSizeLimit": 2097152
"StoredFilesPath": "D:\\tmp\\LargeFileUpload",
"FileSizeLimit": 6442450944
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I calculated this in bytes (6 GiB) but it might actually be in MiB (i.e. 6 TiB). 🤷

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