Restore: improve thread pool starvation fix by disabling asynchronous I/O

src/NuGet.Core/NuGet.Packaging/LocalPackageArchiveDownloader.cs

@@ -176,8 +176,7 @@ public async Task<bool> CopyNupkgFileToAsync(string destinationFilePath, Cancell
                     FileMode.Create,
                     FileAccess.ReadWrite,
                     FileShare.ReadWrite | FileShare.Delete,
-                    bufferSize: 4096,
-                    useAsync: false))
+                    bufferSize: 4096))
                 {
                     // This value comes from NuGet.Protocol.StreamExtensions.CopyToAsync(...).
                     // While 8K may or may not be the optimal buffer size for copy performance,
@@ -285,8 +284,7 @@ private FileStream GetSourceStream()
                FileMode.Open,
                FileAccess.Read,
                FileShare.Read,
-               bufferSize: 4096,
-               useAsync: true);
+               bufferSize: 4096);
         }
 
         private void ThrowIfDisposed()

src/NuGet.Core/NuGet.Packaging/PackageExtractor.cs

@@ -458,12 +458,11 @@ public static async Task<bool> InstallFromSourceAsync(
                             {
                                 // Extract the nupkg
                                 using (var nupkgStream = new FileStream(
-                                        targetTempNupkg,
-                                        FileMode.Create,
-                                        FileAccess.ReadWrite,
-                                        FileShare.ReadWrite | FileShare.Delete,
-                                        bufferSize: 4096,
-                                        useAsync: true))
+                                    targetTempNupkg,
+                                    FileMode.Create,
+                                    FileAccess.ReadWrite,
+                                    FileShare.ReadWrite | FileShare.Delete,
+                                    bufferSize: 4096))
                                 {
                                     await copyToAsync(nupkgStream);
                                     nupkgStream.Seek(0, SeekOrigin.Begin);

src/NuGet.Core/NuGet.Protocol/HttpSource/HttpCacheUtility.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.IO;
-using System.Linq;
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
@@ -67,44 +66,24 @@ public static async Task CreateCacheFileAsync(
             // The update of a cached file is divided into two steps:
             // 1) Delete the old file.
             // 2) Create a new file with the same name.
-
-            // Some FileStream operations on Windows are synchronous even though it may not seem so.
-            // The HTTP stack rewrite in .NET Core 2.1 introduced circumstances whereby these
-            // synchronous FileStream calls will keep an IO completion thread busy and block other
-            // HTTP requests from completing.  The immediate solution is to perform write and read
-            // operations on separate streams, but only on .NET Core where the problem exists.
-            // See https://github.com/dotnet/corefx/issues/31914 for details.
-            const int writeBufferSize =
-#if IS_CORECLR
-                1;  // This disables write buffering.
-#else
-                BufferSize;
-#endif
-
             using (var fileStream = new FileStream(
                 result.NewFile,
                 FileMode.Create,
-                FileAccess.Write,
+                FileAccess.ReadWrite,
                 FileShare.None,
-                writeBufferSize,
-                useAsync: true))
+                BufferSize))
             {
                 using (var networkStream = await response.Content.ReadAsStreamAsync())
                 {
                     await networkStream.CopyToAsync(fileStream, BufferSize, cancellationToken);
                 }
-            }
 
-            using (var fileStream = new FileStream(
-                result.NewFile,
-                FileMode.Open,
-                FileAccess.Read,
-                FileShare.None,
-                BufferSize,
-                useAsync: true))
-            {
                 // Validate the content before putting it into the cache.
-                ensureValidContents?.Invoke(fileStream);
+                if (ensureValidContents != null)
+                {
+                    fileStream.Seek(0, SeekOrigin.Begin);
+                    ensureValidContents.Invoke(fileStream);
+                }
             }
 
             if (File.Exists(result.CacheFile))
@@ -141,8 +120,7 @@ public static async Task CreateCacheFileAsync(
                 FileMode.Open,
                 FileAccess.Read,
                 FileShare.Read | FileShare.Delete,
-                BufferSize,
-                useAsync: true);
+                BufferSize);
         }
     }
-}
+}

src/NuGet.Core/NuGet.Protocol/Plugins/PluginCacheEntry.cs

@@ -87,8 +87,7 @@ public async Task UpdateCacheFileAsync()
                     FileMode.Create,
                     FileAccess.ReadWrite,
                     FileShare.None,
-                    CachingUtility.BufferSize,
-                    useAsync: true))
+                    CachingUtility.BufferSize))
                 {
                     var json = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(OperationClaims, Formatting.Indented));
                     await fileStream.WriteAsync(json, 0, json.Length);
@@ -116,4 +115,4 @@ public async Task UpdateCacheFileAsync()
             }
         }
     }
-}
+}

src/NuGet.Core/NuGet.Protocol/RemotePackageArchiveDownloader.cs

@@ -172,8 +172,7 @@ public async Task<bool> CopyNupkgFileToAsync(string destinationFilePath, Cancell
                     FileMode.Create,
                     FileAccess.ReadWrite,
                     FileShare.ReadWrite | FileShare.Delete,
-                    bufferSize: 4096,
-                    useAsync: true))
+                    bufferSize: 4096))
                 {
                     var result = await _resource.CopyNupkgToStreamAsync(
                         _packageIdentity.Id,
@@ -286,8 +285,7 @@ private FileStream GetDestinationStream()
                FileMode.Open,
                FileAccess.Read,
                FileShare.Read,
-               bufferSize: 4096,
-               useAsync: true);
+               bufferSize: 4096);
         }
 
         private void ThrowIfDisposed()

src/NuGet.Core/NuGet.Protocol/Utility/CachingUtility.cs

@@ -45,8 +45,7 @@ public static Stream ReadCacheFile(TimeSpan maxAge, string cacheFile)
                         FileMode.Open,
                         FileAccess.Read,
                         FileShare.Read | FileShare.Delete,
-                        BufferSize,
-                        useAsync: true);
+                        BufferSize);
 
                     return stream;
                 }
@@ -63,7 +62,7 @@ public static bool IsFileAlreadyOpen(string filePath)
             {
                 stream = new FileStream(filePath, FileMode.Open, FileAccess.ReadWrite, FileShare.None);
             }
-            catch(FileNotFoundException)
+            catch (FileNotFoundException)
             {
                 return false;
             }
@@ -92,4 +91,4 @@ public static string RemoveInvalidFileNameChars(string value)
                 .Replace("__", "_");
         }
     }
-}
+}

src/NuGet.Core/NuGet.Protocol/Utility/FindPackagesByIdNupkgDownloader.cs

@@ -55,7 +55,7 @@ public async Task<NuspecReader> GetNuspecReaderFromNupkgAsync(
             CancellationToken token)
         {
             NuspecReader reader = null;
-            
+
             lock (_nuspecReadersLock)
             {
                 if (_nuspecReaders.TryGetValue(url, out reader))
@@ -76,7 +76,7 @@ await ProcessNupkgStreamAsync(
                 cacheContext,
                 logger,
                 token);
-            
+
             if (reader == null)
             {
                 // The package was not found on the feed. This typically means
@@ -245,7 +245,7 @@ private async Task<CacheEntry> ProcessStreamAndGetCacheEntryAsync(
                 logger,
                 token);
         }
-        
+
         private async Task<T> ProcessHttpSourceResultAsync<T>(
             PackageIdentity identity,
             string url,
@@ -336,8 +336,7 @@ private async Task<bool> ProcessCacheEntryAsync(
                         FileMode.Open,
                         FileAccess.Read,
                         FileShare.ReadWrite | FileShare.Delete,
-                        StreamExtensions.BufferSize,
-                        useAsync: true));
+                        StreamExtensions.BufferSize));
                 },
                 token))
             {
@@ -354,9 +353,9 @@ public CacheEntry(string cacheFile, bool alreadyProcessed)
                 CacheFile = cacheFile;
                 AlreadyProcessed = alreadyProcessed;
             }
-            
+
             public string CacheFile { get; }
             public bool AlreadyProcessed { get; }
         }
     }
-}
+}

src/NuGet.Core/NuGet.Protocol/Utility/GetDownloadResultUtility.cs

@@ -202,7 +202,7 @@ private static async Task<DownloadResourceResult> DirectDownloadAsync(
                    FileAccess.ReadWrite,
                    FileShare.Read,
                    BufferSize,
-                   FileOptions.Asynchronous | FileOptions.DeleteOnClose);
+                   FileOptions.DeleteOnClose);
 
                 await packageStream.CopyToAsync(fileStream, BufferSize, token);
 
@@ -218,4 +218,4 @@ private static async Task<DownloadResourceResult> DirectDownloadAsync(
             }
         }
     }
-}
+}