Method OpenWriter

modules/logging/filewriter.go:187–296

OpenWriter opens a new file writer.

()

// OpenWriter opens a new file writer.
func (fw FileWriter) OpenWriter() (io.WriteCloser, error) {
	modeIfCreating := os.FileMode(fw.Mode)
	if modeIfCreating == 0 {
		modeIfCreating = 0o600
	}

	// roll log files as a sensible default to avoid disk space exhaustion
	roll := fw.Roll == nil || *fw.Roll

	// Ensure directory exists before opening the file.
	dirPath := filepath.Dir(fw.Filename)
	switch strings.ToLower(strings.TrimSpace(fw.DirMode)) {
	case "", "0":
		// Preserve current behavior: locked-down directories by default.
		if err := os.MkdirAll(dirPath, 0o700); err != nil {
			return nil, err
		}
	case "inherit":
		if err := mkdirAllInherit(dirPath); err != nil {
			return nil, err
		}
	case "from_file":
		if err := mkdirAllFromFile(dirPath, os.FileMode(fw.Mode)); err != nil {
			return nil, err
		}
	default:
		dm, err := parseFileMode(fw.DirMode)
		if err != nil {
			return nil, fmt.Errorf("dir_mode: %w", err)
		}
		if err := os.MkdirAll(dirPath, dm); err != nil {
			return nil, err
		}
	}

	// create/open the file
	file, err := os.OpenFile(fw.Filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, modeIfCreating)
	if err != nil {
		return nil, err
	}
	info, err := file.Stat()
	if roll {
		file.Close() // timberjack will reopen it on its own
	}

	// Ensure already existing files have the right mode, since OpenFile will not set the mode in such case.
	if configuredMode := os.FileMode(fw.Mode); configuredMode != 0 {
		if err != nil {
			return nil, fmt.Errorf("unable to stat log file to see if we need to set permissions: %v", err)
		}
		// only chmod if the configured mode is different
		if info.Mode()&os.ModePerm != configuredMode&os.ModePerm {
			if err = os.Chmod(fw.Filename, configuredMode); err != nil {
				return nil, err
			}
		}
	}