xl: getPartsMetadata fetch parts and decode in go-routine. (#1569)

Ref #1516

xl-erasure-v1-common.go

@@ -19,6 +19,7 @@ package main
 import (
 	"errors"
 	slashpath "path"
+	"sync"
 
 	"github.com/Sirupsen/logrus"
 )
@@ -117,12 +118,16 @@ func (xl XL) getPartsMetadata(volume, path string) ([]xlMetaV1, []error) {
 	errs := make([]error, len(xl.storageDisks))
 	metadataArray := make([]xlMetaV1, len(xl.storageDisks))
 	xlMetaV1FilePath := slashpath.Join(path, xlMetaV1File)
+	var wg = &sync.WaitGroup{}
 	for index, disk := range xl.storageDisks {
+		wg.Add(1)
+		go func(index int, disk StorageAPI) {
+			defer wg.Done()
 			offset := int64(0)
 			metadataReader, err := disk.ReadFile(volume, xlMetaV1FilePath, offset)
 			if err != nil {
 				errs[index] = err
-			continue
+				return
 			}
 			defer metadataReader.Close()
 
@@ -130,10 +135,12 @@ func (xl XL) getPartsMetadata(volume, path string) ([]xlMetaV1, []error) {
 			if err != nil {
 				// Unable to parse file.json, set error.
 				errs[index] = err
-			continue
+				return
 			}
 			metadataArray[index] = metadata
+		}(index, disk)
 	}
+	wg.Wait()
 	return metadataArray, errs
 }