fix(access_log): file size calculation

internal/logging/accesslog/back_scanner.go

@@ -26,12 +26,8 @@ type BackScanner struct {
 
 // NewBackScanner creates a new Scanner to read the file backward.
 // chunkSize determines the size of each read chunk from the end of the file.
-func NewBackScanner(file ReaderAtSeeker, chunkSize int) *BackScanner {
+func NewBackScanner(file ReaderAtSeeker, fileSize int64, chunkSize int) *BackScanner {
-	size, err := file.Seek(0, io.SeekEnd)
+	return newBackScanner(file, fileSize, make([]byte, chunkSize))
-	if err != nil {
-		return &BackScanner{err: err}
-	}
-	return newBackScanner(file, size, make([]byte, chunkSize))
 }
 
 func newBackScanner(file ReaderAtSeeker, fileSize int64, buf []byte) *BackScanner {
@@ -111,11 +107,6 @@ func (s *BackScanner) Bytes() []byte {
 	return s.line
 }
 
-// FileSize returns the size of the file.
-func (s *BackScanner) FileSize() int64 {
-	return s.size
-}
-
 // Err returns the first non-EOF error encountered by the scanner.
 func (s *BackScanner) Err() error {
 	return s.err

internal/logging/accesslog/file_logger.go

@@ -72,6 +72,14 @@ func (f *File) Seek(offset int64, whence int) (int64, error) {
 	return f.f.Seek(offset, whence)
 }
 
+func (f *File) Size() (int64, error) {
+	stat, err := f.f.Stat()
+	if err != nil {
+		return 0, err
+	}
+	return stat.Size(), nil
+}
+
 func (f *File) Truncate(size int64) error {
 	return f.f.Truncate(size)
 }

internal/logging/accesslog/rotate.go

@@ -16,6 +16,7 @@ type supportRotate interface {
 	io.ReaderAt
 	io.WriterAt
 	Truncate(size int64) error
+	Size() (int64, error)
 }
 
 type RotateResult struct {
@@ -96,9 +97,14 @@ func rotateLogFileByPolicy(file supportRotate, config *Retention) (result *Rotat
 		return nil, nil // should not happen
 	}
 
-	s := NewBackScanner(file, defaultChunkSize)
+	fileSize, err := file.Size()
+	if err != nil {
+		return nil, err
+	}
+
+	s := NewBackScanner(file, fileSize, defaultChunkSize)
 	result = &RotateResult{
-		OriginalSize: s.FileSize(),
+		OriginalSize: fileSize,
 	}
 
 	// nothing to rotate, return the nothing
@@ -201,7 +207,7 @@ func rotateLogFileByPolicy(file supportRotate, config *Retention) (result *Rotat
 //
 // Invalid lines will not be detected and included in the result.
 func rotateLogFileBySize(file supportRotate, config *Retention) (result *RotateResult, err error) {
-	filesize, err := file.Seek(0, io.SeekEnd)
+	filesize, err := file.Size()
 	if err != nil {
 		return nil, err
 	}