perf: add buffering to `FileWritingService` (#435)

src/Microsoft.ComponentDetection.Common/FileWritingService.cs

@@ -1,14 +1,17 @@
 namespace Microsoft.ComponentDetection.Common;
 using System;
+using System.Collections.Concurrent;
 using System.IO;
+using System.Threading.Tasks;
 using Microsoft.ComponentDetection.Common.Exceptions;
 
-public class FileWritingService : IFileWritingService
+public sealed class FileWritingService : IFileWritingService
 {
     public const string TimestampFormatString = "yyyyMMddHHmmssfff";
 
     private readonly object lockObject = new object();
     private readonly string timestamp = DateTime.Now.ToString(TimestampFormatString);
+    private readonly ConcurrentDictionary<string, StreamWriter> bufferedStreams = new();
 
     public string BasePath { get; private set; }
 
@@ -26,10 +29,13 @@ public class FileWritingService : IFileWritingService
     {
         relativeFilePath = this.ResolveFilePath(relativeFilePath);
 
-        lock (this.lockObject)
+        if (!this.bufferedStreams.TryGetValue(relativeFilePath, out var streamWriter))
         {
-            File.AppendAllText(relativeFilePath, text);
+            streamWriter = new StreamWriter(relativeFilePath, true);
+            this.bufferedStreams.TryAdd(relativeFilePath, streamWriter);
         }
+
+        streamWriter.Write(text);
     }
 
     public void WriteFile(string relativeFilePath, string text)
@@ -66,4 +72,33 @@ public class FileWritingService : IFileWritingService
             throw new InvalidOperationException("Base path has not yet been initialized in File Writing Service!");
         }
     }
+
+    private void Dispose(bool disposing)
+    {
+        if (!disposing)
+        {
+            return;
+        }
+
+        foreach (var (filename, streamWriter) in this.bufferedStreams)
+        {
+            streamWriter.Dispose();
+            this.bufferedStreams.TryRemove(filename, out _);
+        }
+    }
+
+    public void Dispose()
+    {
+        this.Dispose(true);
+        GC.SuppressFinalize(this);
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        foreach (var (filename, streamWriter) in this.bufferedStreams)
+        {
+            await streamWriter.DisposeAsync();
+            this.bufferedStreams.TryRemove(filename, out _);
+        }
+    }
 }

src/Microsoft.ComponentDetection.Common/IFileWritingService.cs

@@ -1,8 +1,10 @@
 namespace Microsoft.ComponentDetection.Common;
+
+using System;
 using System.IO;
 
 // All file paths are relative and will replace occurrences of {timestamp} with the shared file timestamp.
-public interface IFileWritingService
+public interface IFileWritingService : IDisposable, IAsyncDisposable
 {
     void Init(string basePath);
 

src/Microsoft.ComponentDetection/Program.cs

@@ -32,6 +32,9 @@ try
 
     Console.WriteLine($"Execution finished, status: {exitCode}.");
 
+    // Manually dispose to flush logs as we force exit
+    await serviceProvider.DisposeAsync();
+
     // force an exit, not letting any lingering threads not responding.
     Environment.Exit(exitCode);
 }

test/Microsoft.ComponentDetection.Common.Tests/FileWritingServiceTests.cs

@@ -41,6 +41,7 @@ public class FileWritingServiceTests
         var fileLocation = Path.Combine(this.tempFolder, relativeDir);
         File.Create(fileLocation).Dispose();
         this.serviceUnderTest.AppendToFile(relativeDir, "someSampleText");
+        this.serviceUnderTest.Dispose();
         var text = File.ReadAllText(Path.Combine(this.tempFolder, relativeDir));
         text
             .Should().Be("someSampleText");
@@ -62,6 +63,7 @@ public class FileWritingServiceTests
         var relativeDir = "somefile_{timestamp}.txt";
         this.serviceUnderTest.WriteFile(relativeDir, "sampleText");
         this.serviceUnderTest.AppendToFile(relativeDir, "sampleText2");
+        this.serviceUnderTest.Dispose();
         var files = Directory.GetFiles(this.tempFolder);
         files
             .Should().NotBeEmpty();