refactor(store): extract (*Store).saveChunk method (#15144)

store/snapshots/store.go

@@ -3,6 +3,7 @@ package snapshots
 import (
 	"crypto/sha256"
 	"encoding/binary"
+	"hash"
 	"io"
 	"math"
 	"os"
@@ -256,37 +257,27 @@ func (s *Store) Save(
 		Height: height,
 		Format: format,
 	}
+
+	dirCreated := false
 	index := uint32(0)
 	snapshotHasher := sha256.New()
 	chunkHasher := sha256.New()
 	for chunkBody := range chunks {
-		defer chunkBody.Close() //nolint:staticcheck
-		dir := s.pathSnapshot(height, format)
-		err = os.MkdirAll(dir, 0o755)
-		if err != nil {
-			return nil, errors.Wrapf(err, "failed to create snapshot directory %q", dir)
-		}
-		path := s.pathChunk(height, format, index)
-		file, err := os.Create(path)
-		if err != nil {
-			return nil, errors.Wrapf(err, "failed to create snapshot chunk file %q", path)
-		}
-		defer file.Close() //nolint:staticcheck
+		// Only create the snapshot directory on encountering the first chunk.
+		// If the directory disappears during chunk saving,
+		// the whole operation will fail anyway.
+		if !dirCreated {
+			dir := s.pathSnapshot(height, format)
+			if err := os.MkdirAll(dir, 0o755); err != nil {
+				return nil, errors.Wrapf(err, "failed to create snapshot directory %q", dir)
+			}
 
-		chunkHasher.Reset()
-		_, err = io.Copy(io.MultiWriter(file, chunkHasher, snapshotHasher), chunkBody)
-		if err != nil {
-			return nil, errors.Wrapf(err, "failed to generate snapshot chunk %v", index)
+			dirCreated = true
 		}
-		err = file.Close()
-		if err != nil {
-			return nil, errors.Wrapf(err, "failed to close snapshot chunk %v", index)
+
+		if err := s.saveChunk(chunkBody, index, snapshot, chunkHasher, snapshotHasher); err != nil {
+			return nil, err
 		}
-		err = chunkBody.Close()
-		if err != nil {
-			return nil, errors.Wrapf(err, "failed to close snapshot chunk %v", index)
-		}
-		snapshot.Metadata.ChunkHashes = append(snapshot.Metadata.ChunkHashes, chunkHasher.Sum(nil))
 		index++
 	}
 	snapshot.Chunks = index
@@ -294,6 +285,36 @@ func (s *Store) Save(
 	return snapshot, s.saveSnapshot(snapshot)
 }
 
+// saveChunk saves the given chunkBody with the given index to its appropriate path on disk.
+// The hash of the chunk is appended to the snapshot's metadata,
+// and the overall snapshot hash is updated with the chunk content too.
+func (s *Store) saveChunk(chunkBody io.ReadCloser, index uint32, snapshot *types.Snapshot, chunkHasher, snapshotHasher hash.Hash) error {
+	defer chunkBody.Close()
+
+	path := s.pathChunk(snapshot.Height, snapshot.Format, index)
+	chunkFile, err := os.Create(path)
+	if err != nil {
+		return errors.Wrapf(err, "failed to create snapshot chunk file %q", path)
+	}
+	defer chunkFile.Close()
+
+	chunkHasher.Reset()
+	if _, err := io.Copy(io.MultiWriter(chunkFile, chunkHasher, snapshotHasher), chunkBody); err != nil {
+		return errors.Wrapf(err, "failed to generate snapshot chunk %d", index)
+	}
+
+	if err := chunkFile.Close(); err != nil {
+		return errors.Wrapf(err, "failed to close snapshot chunk file %d", index)
+	}
+
+	if err := chunkBody.Close(); err != nil {
+		return errors.Wrapf(err, "failed to close snapshot chunk body %d", index)
+	}
+
+	snapshot.Metadata.ChunkHashes = append(snapshot.Metadata.ChunkHashes, chunkHasher.Sum(nil))
+	return nil
+}
+
 // saveSnapshot saves snapshot metadata to the database.
 func (s *Store) saveSnapshot(snapshot *types.Snapshot) error {
 	value, err := proto.Marshal(snapshot)