Larger buffer for file and network operations. (#704)

* larger buffer for stream copy

* Argument checks.

* configuration for package downloader.

* Using the default value for buffer size.

* Removed explicit package downloader configuration

* Comment on buffer size for file streams.

src/Validation.Common.Job/FileStreamUtility.cs

@@ -7,7 +7,14 @@ namespace NuGet.Jobs.Validation
 {
     public static class FileStreamUtility
     {
-        public const int BufferSize = 8192;
+        /// <summary>
+        /// The buffer size to use for file operations.
+        /// </summary>
+        /// <remarks>
+        /// The value is chosen to align with the default Stream buffer size:
+        /// https://github.com/dotnet/corefx/blob/master/src/Common/src/CoreLib/System/IO/Stream.cs#L32-L35
+        /// </remarks>
+        private const int BufferSize = 80 * 1024;
 
         public static FileStream GetTemporaryFile()
         {

src/Validation.Common.Job/PackageDownloader.cs

@@ -9,27 +9,49 @@
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 
 namespace NuGet.Jobs.Validation
 {
     public class PackageDownloader : IFileDownloader
     {
         private readonly HttpClient _httpClient;
         private readonly ICommonTelemetryService _telemetryService;
+        private readonly PackageDownloaderConfiguration _configuration;
         private readonly ILogger<PackageDownloader> _logger;
 
         public PackageDownloader(
             HttpClient httpClient,
             ICommonTelemetryService telemetryService,
+            IOptionsSnapshot<PackageDownloaderConfiguration> downloaderConfigurationAccessor,
             ILogger<PackageDownloader> logger)
         {
             _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
             _telemetryService = telemetryService ?? throw new ArgumentNullException(nameof(telemetryService));
+            if (downloaderConfigurationAccessor == null)
+            {
+                throw new ArgumentNullException(nameof(downloaderConfigurationAccessor));
+            }
+            if (downloaderConfigurationAccessor.Value.BufferSize <= 0)
+            {
+                throw new ArgumentException($"{nameof(downloaderConfigurationAccessor.Value.BufferSize)} cannot be less than 1", nameof(downloaderConfigurationAccessor));
+            }
+            _configuration = downloaderConfigurationAccessor.Value;
             _logger = logger ?? throw new ArgumentNullException(nameof(logger));
         }
 
         public async Task<Stream> DownloadAsync(Uri packageUri, CancellationToken cancellationToken)
         {
+            if (packageUri == null)
+            {
+                throw new ArgumentNullException(nameof(packageUri));
+            }
+
+            if (cancellationToken == null)
+            {
+                throw new ArgumentNullException(nameof(cancellationToken));
+            }
+
             _logger.LogInformation("Attempting to download package from {PackageUri}...", packageUri);
 
             Stream packageStream = null;
@@ -56,7 +78,7 @@ public async Task<Stream> DownloadAsync(Uri packageUri, CancellationToken cancel
                     {
                         packageStream = FileStreamUtility.GetTemporaryFile();
 
-                        await networkStream.CopyToAsync(packageStream, FileStreamUtility.BufferSize, cancellationToken);
+                        await networkStream.CopyToAsync(packageStream, _configuration.BufferSize, cancellationToken);
                     }
                 }
 

src/Validation.Common.Job/PackageDownloaderConfiguration.cs

@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+namespace NuGet.Jobs.Validation
+{
+    public class PackageDownloaderConfiguration
+    {
+        /// <summary>
+        /// The size of the buffer used to copy the network stream.
+        /// </summary>
+        /// <remarks>Implementation uses the <see cref="System.IO.Stream.CopyToAsync(System.IO.Stream, int, System.Threading.CancellationToken)"/>
+        /// passing that value as the second argument.
+        /// 
+        /// Setting the package downloader default buffer size to the buffer size used for copying streams
+        /// see https://github.com/dotnet/corefx/blob/master/src/Common/src/CoreLib/System/IO/Stream.cs#L32-L35
+        /// </remarks>
+        public int BufferSize { get; set; } = 80 * 1024;
+    }
+}

src/Validation.Common.Job/Validation.Common.Job.csproj

@@ -51,6 +51,7 @@
     <Compile Include="LoggerDiagnosticsService.cs" />
     <Compile Include="LoggerDiagnosticsSource.cs" />
     <Compile Include="PackageDownloader.cs" />
+    <Compile Include="PackageDownloaderConfiguration.cs" />
     <Compile Include="PathUtility.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Properties\AssemblyInfo.*.cs" />