[not-fixup] - Reduce memory consumption for Buffered File Writer (#2377)

* correctly use the buffered file writer

* use value from source

* reorder fields

* use only the DetectorKey as a map field

* correctly use the buffered file writer

* use value from source

* reorder fields

* add tests and update

* Fix issue with buffer slices growing

* fix test

* fix

* add singleton

* use shared pool

* optimize

* rename and cleanup

* use correct calculation to grow buffer

* only grow if needed

* address comments

* remove unused

* remove

* rip out Grow

* address coment

* use 2k default buffer

* update comment allow large buffers to be garbage collected

pkg/gitparse/gitparse.go

@@ -449,7 +449,6 @@ func (c *Parser) FromReader(ctx context.Context, stdOut io.Reader, commitChan ch
 			}
 			// Create a new currentDiff and currentCommit
 			currentDiff = diff()
-			// currentDiff = NewDiff(withCustomContentWriter(c.contentWriter()))
 			currentCommit = &Commit{Message: strings.Builder{}}
 			// Check that the commit line contains a hash and set it.
 			if len(line) >= 47 {

pkg/writers/buffered_file_writer/bufferedfilewriter.go

@@ -13,12 +13,59 @@ import (
 	"github.com/trufflesecurity/trufflehog/v3/pkg/context"
 )
 
-// bufferPool is used to store buffers for reuse.
-var bufferPool = sync.Pool{
-	// TODO: Consider growing the buffer before returning it if we can find an optimal size.
-	// Ideally the size would cover the majority of cases without being too large.
-	// This would avoid the need to grow the buffer when writing to it, reducing allocations.
-	New: func() any { return new(bytes.Buffer) },
+type bufPoolOpt func(pool *bufferPool)
+
+type bufferPool struct {
+	bufferSize uint32
+	*sync.Pool
+}
+
+const defaultBufferSize = 2 << 10 // 2KB
+func newBufferPool(opts ...bufPoolOpt) *bufferPool {
+	pool := &bufferPool{bufferSize: defaultBufferSize}
+
+	for _, opt := range opts {
+		opt(pool)
+	}
+	pool.Pool = &sync.Pool{
+		New: func() any {
+			buf := new(bytes.Buffer)
+			buf.Grow(int(pool.bufferSize))
+			return buf
+		},
+	}
+
+	return pool
+}
+
+// sharedBufferPool is the shared buffer pool used by all BufferedFileWriters.
+// This allows for efficient reuse of buffers across multiple writers.
+var sharedBufferPool *bufferPool
+
+func init() { sharedBufferPool = newBufferPool() }
+
+func (bp *bufferPool) get(ctx context.Context) *bytes.Buffer {
+	buf, ok := bp.Pool.Get().(*bytes.Buffer)
+	if !ok {
+		ctx.Logger().Error(fmt.Errorf("buffer pool returned unexpected type"), "using new buffer")
+		buf = bytes.NewBuffer(make([]byte, 0, bp.bufferSize))
+	}
+
+	return buf
+}
+
+func (bp *bufferPool) put(buf *bytes.Buffer) {
+	// If the buffer is more than twice the default size, release it for garbage collection.
+	// This prevents us from returning very large buffers to the pool.
+	const maxAllowedCapacity = 2 * defaultBufferSize
+	if buf.Cap() > maxAllowedCapacity {
+		buf = nil // Release the large buffer for garbage collection.
+	} else {
+		// Reset the buffer to clear any existing data.
+		buf.Reset()
+	}
+
+	bp.Put(buf)
 }
 
 // state represents the current mode of BufferedFileWriter.
@@ -39,7 +86,8 @@ type BufferedFileWriter struct {
 
 	state state // Current state of the writer. (writeOnly or readOnly)
 
-	buf      bytes.Buffer   // Buffer for storing data under the threshold in memory.
+	bufPool  *bufferPool    // Pool for storing buffers for reuse.
+	buf      *bytes.Buffer  // Buffer for storing data under the threshold in memory.
 	filename string         // Name of the temporary file.
 	file     io.WriteCloser // File for storing data over the threshold.
 }
@@ -55,7 +103,11 @@ func WithThreshold(threshold uint64) Option {
 // New creates a new BufferedFileWriter with the given options.
 func New(opts ...Option) *BufferedFileWriter {
 	const defaultThreshold = 10 * 1024 * 1024 // 10MB
-	w := &BufferedFileWriter{threshold: defaultThreshold, state: writeOnly}
+	w := &BufferedFileWriter{
+		threshold: defaultThreshold,
+		state:     writeOnly,
+		bufPool:   sharedBufferPool,
+	}
 	for _, opt := range opts {
 		opt(w)
 	}
@@ -78,17 +130,16 @@ func (w *BufferedFileWriter) String() (string, error) {
 	}
 	defer file.Close()
 
-	// Create a buffer large enough to hold file data and additional buffer data, if any.
-	fileSize := w.size
-	buf := bytes.NewBuffer(make([]byte, 0, fileSize))
-
+	var buf bytes.Buffer
 	// Read the file contents into the buffer.
-	if _, err := io.Copy(buf, file); err != nil {
+	if _, err := io.CopyBuffer(&buf, file, nil); err != nil {
 		return "", fmt.Errorf("failed to read file contents: %w", err)
 	}
 
 	// Append buffer data, if any, to the end of the file contents.
-	buf.Write(w.buf.Bytes())
+	if _, err := w.buf.WriteTo(&buf); err != nil {
+		return "", err
+	}
 
 	return buf.String(), nil
 }
@@ -100,33 +151,44 @@ func (w *BufferedFileWriter) Write(ctx context.Context, data []byte) (int, error
 	}
 
 	size := uint64(len(data))
+
+	if w.buf == nil || w.buf.Len() == 0 {
+		w.buf = w.bufPool.get(ctx)
+	}
+
+	bufferLength := w.buf.Len()
+
 	defer func() {
 		w.size += size
 		ctx.Logger().V(4).Info(
 			"write complete",
 			"data_size", size,
-			"content_size", w.buf.Len(),
+			"content_size", bufferLength,
 			"total_size", w.size,
 		)
 	}()
 
-	if w.buf.Len() == 0 {
-		bufPtr, ok := bufferPool.Get().(*bytes.Buffer)
-		if !ok {
-			ctx.Logger().Error(fmt.Errorf("buffer pool returned unexpected type"), "using new buffer")
-			bufPtr = new(bytes.Buffer)
-		}
-		bufPtr.Reset() // Reset the buffer to clear any existing data
-		w.buf = *bufPtr
-	}
-
-	if uint64(w.buf.Len())+size <= w.threshold {
+	totalSizeNeeded := uint64(bufferLength) + uint64(len(data))
+	if totalSizeNeeded <= w.threshold {
 		// If the total size is within the threshold, write to the buffer.
 		ctx.Logger().V(4).Info(
 			"writing to buffer",
 			"data_size", size,
-			"content_size", w.buf.Len(),
+			"content_size", bufferLength,
 		)
+
+		availableSpace := w.buf.Cap() - bufferLength
+		growSize := int(totalSizeNeeded) - bufferLength
+		if growSize > availableSpace {
+			ctx.Logger().V(4).Info(
+				"buffer size exceeded, growing buffer",
+				"current_size", bufferLength,
+				"new_size", totalSizeNeeded,
+				"available_space", availableSpace,
+				"grow_size", growSize,
+			)
+		}
+
 		return w.buf.Write(data)
 	}
 
@@ -143,14 +205,12 @@ func (w *BufferedFileWriter) Write(ctx context.Context, data []byte) (int, error
 
 		// Transfer existing data in buffer to the file, then clear the buffer.
 		// This ensures all the data is in one place - either entirely in the buffer or the file.
-		if w.buf.Len() > 0 {
-			ctx.Logger().V(4).Info("writing buffer to file", "content_size", w.buf.Len())
-			if _, err := w.file.Write(w.buf.Bytes()); err != nil {
+		if bufferLength > 0 {
+			ctx.Logger().V(4).Info("writing buffer to file", "content_size", bufferLength)
+			if _, err := w.buf.WriteTo(w.file); err != nil {
 				return 0, err
 			}
-			// Reset the buffer to clear any existing data and return it to the pool.
-			w.buf.Reset()
-			bufferPool.Put(&w.buf)
+			w.bufPool.put(w.buf)
 		}
 	}
 	ctx.Logger().V(4).Info("writing to file", "data_size", size)
@@ -167,7 +227,7 @@ func (w *BufferedFileWriter) CloseForWriting() error {
 	}
 
 	if w.buf.Len() > 0 {
-		_, err := w.file.Write(w.buf.Bytes())
+		_, err := w.buf.WriteTo(w.file)
 		if err != nil {
 			return err
 		}
@@ -199,7 +259,7 @@ func (w *BufferedFileWriter) ReadCloser() (io.ReadCloser, error) {
 	// Data is in memory.
 	return &bufferReadCloser{
 		Reader:  bytes.NewReader(w.buf.Bytes()),
-		onClose: func() { bufferPool.Put(&w.buf) },
+		onClose: func() { w.bufPool.put(w.buf) },
 	}, nil
 }