refactor(lib/metainfogen): deduplicate metainfo generation

lib/metainfogen/generator.go

@@ -18,7 +18,6 @@ import (
 
 	"github.com/uber/kraken/core"
 	"github.com/uber/kraken/lib/store"
-	"github.com/uber/kraken/lib/store/metadata"
 )
 
 // Generator wraps static piece length configuration in order to determinstically
@@ -43,19 +42,8 @@ func (g *Generator) Generate(d core.Digest) error {
 	if err != nil {
 		return fmt.Errorf("cache stat: %s", err)
 	}
-	f, err := g.cas.GetCacheFileReader(d.Hex())
-	if err != nil {
-		return fmt.Errorf("get cache file: %s", err)
-	}
 	pieceLength := g.pieceLengthConfig.get(info.Size())
-	mi, err := core.NewMetaInfo(d, f, pieceLength)
-	if err != nil {
-		return fmt.Errorf("create metainfo: %s", err)
-	}
-	if _, err := g.cas.SetCacheFileMetadata(d.Hex(), metadata.NewTorrentMeta(mi)); err != nil {
-		return fmt.Errorf("set metainfo: %s", err)
-	}
-	return nil
+	return g.cas.GenerateCacheFileMetaInfo(d, pieceLength)
 }
 
 // Get the piece length for the blob

lib/store/ca_store.go

@@ -310,10 +310,17 @@ func (s *CAStore) generateMetadataFromFile(name string, pieceLength int64) error
 	if err != nil {
 		return fmt.Errorf("get digest from file: %w", err)
 	}
-	f, err := s.GetCacheFileReader(name)
+	return s.GenerateCacheFileMetaInfo(d, pieceLength)
+}
+
+// GenerateCacheFileMetaInfo generates torrent metainfo for a cached blob
+// and persists it alongside the cache file.
+func (s *CAStore) GenerateCacheFileMetaInfo(d core.Digest, pieceLength int64) error {
+	f, err := s.GetCacheFileReader(d.Hex())
 	if err != nil {
 		return fmt.Errorf("get cache file: %w", err)
 	}
+	defer closers.Close(f)
 	mi, err := core.NewMetaInfo(d, f, pieceLength)
 	if err != nil {
 		return fmt.Errorf("create metainfo: %w", err)

lib/store/ca_store_test.go

@@ -243,6 +243,50 @@ func TestCAStoreCreateCacheFile(t *testing.T) {
 	require.NoError(err)
 	require.Equal(s1, string(b2))
 }
+
+func TestCAStore_GenerateCacheFileMetaInfo(t *testing.T) {
+	require := require.New(t)
+
+	s, cleanup := CAStoreFixture()
+	defer cleanup()
+
+	const pieceLength = 10
+	blob := core.SizedBlobFixture(100, pieceLength)
+	require.NoError(s.CreateCacheFile(blob.Digest.Hex(), bytes.NewReader(blob.Content)))
+
+	require.NoError(s.GenerateCacheFileMetaInfo(blob.Digest, pieceLength))
+
+	var tm metadata.TorrentMeta
+	require.NoError(s.GetCacheFileMetadata(blob.Digest.Hex(), &tm))
+	require.Equal(blob.MetaInfo, tm.MetaInfo)
+}
+
+func TestCAStore_GenerateCacheFileMetaInfo_CacheFileMissing(t *testing.T) {
+	require := require.New(t)
+
+	s, cleanup := CAStoreFixture()
+	defer cleanup()
+
+	err := s.GenerateCacheFileMetaInfo(core.DigestFixture(), 10)
+	require.ErrorContains(err, "get cache file")
+}
+
+func TestCAStore_GenerateCacheFileMetaInfo_InvalidPieceLength(t *testing.T) {
+	require := require.New(t)
+
+	s, cleanup := CAStoreFixture()
+	defer cleanup()
+
+	blob := core.NewBlobFixture()
+	require.NoError(s.CreateCacheFile(blob.Digest.Hex(), bytes.NewReader(blob.Content)))
+
+	err := s.GenerateCacheFileMetaInfo(blob.Digest, 0)
+	require.EqualError(err, "create metainfo: piece length must be positive")
+
+	var tm metadata.TorrentMeta
+	require.Error(s.GetCacheFileMetadata(blob.Digest.Hex(), &tm))
+}
+
 func TestCAStoreConfig_WithMemoryCache(t *testing.T) {
 	require := require.New(t)