Merge pull request #20 from useblacksmith/sync-bbolt-on-close

boltutil: sync bbolt databases on close to prevent corruption

Author: adityamaru

util/db/boltutil/db.go

@@ -2,15 +2,40 @@ package boltutil
 
 import (
 	"io/fs"
+	"sync"
 
+	"github.com/moby/buildkit/util/bklog"
 	"github.com/moby/buildkit/util/db"
 	bolt "go.etcd.io/bbolt"
 )
 
+// syncingDB wraps a bolt.DB to ensure data is synced to disk before closing.
+// This is important when using NoSync mode, as otherwise dirty pages may not
+// be flushed to disk before unmount, leading to corruption on network block
+// devices or when taking filesystem snapshots.
+type syncingDB struct {
+	*bolt.DB
+	closeOnce sync.Once
+	closeErr  error
+}
+
+// Close syncs the database to disk before closing.
+// This ensures all pending writes are flushed even when NoSync is enabled,
+// preventing corruption during graceful shutdown. Safe to call multiple times.
+func (s *syncingDB) Close() error {
+	s.closeOnce.Do(func() {
+		if err := s.Sync(); err != nil {
+			bklog.L.Warnf("failed to sync database before close: %v", err)
+		}
+		s.closeErr = s.DB.Close()
+	})
+	return s.closeErr
+}
+
 func Open(p string, mode fs.FileMode, options *bolt.Options) (db.DB, error) {
 	bdb, err := bolt.Open(p, mode, options)
 	if err != nil {
 		return nil, err
 	}
-	return bdb, nil
+	return &syncingDB{DB: bdb}, nil
 }