feat(backup): add validated archives and recoverable restore journals

internal/backup/log.go

@@ -0,0 +1,95 @@
+package backup
+
+import (
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// LogWriter 保留三份各不超过 10 MiB 的应用日志，权限 0600。
+type LogWriter struct {
+	mu   sync.Mutex
+	dir  string
+	file *os.File
+	size int64
+}
+
+func OpenLog(dir string) (*LogWriter, error) {
+	if err := os.MkdirAll(dir, 0700); err != nil {
+		return nil, err
+	}
+	f, err := os.OpenFile(filepath.Join(dir, "rawmark.log"), os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
+	if err != nil {
+		return nil, err
+	}
+	info, err := f.Stat()
+	if err != nil {
+		f.Close()
+		return nil, err
+	}
+	return &LogWriter{dir: dir, file: f, size: info.Size()}, nil
+}
+func (l *LogWriter) Write(p []byte) (int, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if len(p) > 10<<20 {
+		return 0, errors.New("单条日志超过大小上限")
+	}
+	if l.size+int64(len(p)) > 10<<20 {
+		if err := l.file.Close(); err != nil {
+			return 0, err
+		}
+		for i := 2; i >= 1; i-- {
+			dest := filepath.Join(l.dir, "rawmark.log.2")
+			src := filepath.Join(l.dir, "rawmark.log.1")
+			if i == 1 {
+				dest = src
+				src = filepath.Join(l.dir, "rawmark.log")
+			}
+			if err := os.Rename(src, dest); err != nil && !errors.Is(err, os.ErrNotExist) {
+				return 0, err
+			}
+		}
+		f, err := os.OpenFile(filepath.Join(l.dir, "rawmark.log"), os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
+		if err != nil {
+			return 0, err
+		}
+		l.file = f
+		l.size = 0
+	}
+	n, err := l.file.Write(p)
+	l.size += int64(n)
+	return n, err
+}
+func (l *LogWriter) Close() error { l.mu.Lock(); defer l.mu.Unlock(); return l.file.Close() }
+
+// Snapshot 读取当前日志的稳定副本，避免导出与日志轮转竞争。
+func (l *LogWriter) Snapshot(dest string) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	if err := l.file.Sync(); err != nil {
+		return err
+	}
+	for _, name := range []string{"rawmark.log", "rawmark.log.1", "rawmark.log.2"} {
+		src, err := os.Open(filepath.Join(l.dir, name))
+		if errors.Is(err, os.ErrNotExist) {
+			continue
+		}
+		if err != nil {
+			return err
+		}
+		out, err := os.OpenFile(filepath.Join(dest, name), os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0600)
+		if err != nil {
+			src.Close()
+			return err
+		}
+		_, err = io.Copy(out, src)
+		err = errors.Join(err, src.Close(), out.Close())
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}