Reduce repo indexer disk usage (#3452)

vendor/github.com/ethantkoenig/rupture/metadata.go

@@ -0,0 +1,68 @@
+package rupture
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+const metaFilename = "rupture_meta.json"
+
+func indexMetadataPath(dir string) string {
+	return filepath.Join(dir, metaFilename)
+}
+
+// IndexMetadata contains metadata about a bleve index.
+type IndexMetadata struct {
+	// The version of the data in the index. This can be useful for tracking
+	// schema changes or data migrations.
+	Version int `json:"version"`
+}
+
+// in addition to the user-exposed metadata, we keep additional, internal-only
+// metadata for sharded indices.
+const shardedMetadataFilename = "rupture_sharded_meta.json"
+
+func shardedIndexMetadataPath(dir string) string {
+	return filepath.Join(dir, shardedMetadataFilename)
+}
+
+type shardedIndexMetadata struct {
+	NumShards int `json:"num_shards"`
+}
+
+func readJSON(path string, meta interface{}) error {
+	metaBytes, err := ioutil.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(metaBytes, meta)
+}
+
+func writeJSON(path string, meta interface{}) error {
+	metaBytes, err := json.Marshal(meta)
+	if err != nil {
+		return err
+	}
+	return ioutil.WriteFile(path, metaBytes, 0666)
+}
+
+// ReadIndexMetadata returns the metadata for the index at the specified path.
+// If no such index metadata exists, an empty metadata and a nil error are
+// returned.
+func ReadIndexMetadata(path string) (*IndexMetadata, error) {
+	meta := &IndexMetadata{}
+	metaPath := indexMetadataPath(path)
+	if _, err := os.Stat(metaPath); os.IsNotExist(err) {
+		return meta, nil
+	} else if err != nil {
+		return nil, err
+	}
+	return meta, readJSON(metaPath, meta)
+}
+
+// WriteIndexMetadata writes metadata for the index at the specified path.
+func WriteIndexMetadata(path string, meta *IndexMetadata) error {
+	return writeJSON(indexMetadataPath(path), meta)
+}