Fix backend format for disk-cache - not to use FS format.json (#5732)

cmd/format-disk-cache.go

@@ -21,9 +21,7 @@ import (
 	"fmt"
 	"io"
 	"os"
-	"path/filepath"
 	"reflect"
-	"syscall"
 
 	errors2 "github.com/minio/minio/pkg/errors"
 )
@@ -36,6 +34,8 @@ const (
 	formatCacheVersionV1 = "1"
 
 	formatMetaVersion1 = "1"
+
+	formatCacheV1DistributionAlgo = "CRCMOD"
 )
 
 // Represents the current cache structure with list of
@@ -49,6 +49,9 @@ type formatCacheV1 struct {
 		// Disks field carries the input disk order generated the first
 		// time when fresh disks were supplied.
 		Disks []string `json:"disks"`
+		// Distribution algorithm represents the hashing algorithm
+		// to pick the right set index for an object.
+		DistributionAlgo string `json:"distributionAlgo"`
 	} `json:"cache"` // Cache field holds cache format.
 }
 
@@ -71,6 +74,7 @@ func newFormatCacheV1(drives []string) []*formatCacheV1 {
 		format.Version = formatMetaVersion1
 		format.Format = formatCache
 		format.Cache.Version = formatCacheVersionV1
+		format.Cache.DistributionAlgo = formatCacheV1DistributionAlgo
 		format.Cache.This = mustGetUUID()
 		formats[i] = format
 		disks[i] = formats[i].Cache.This
@@ -116,28 +120,25 @@ func createFormatCache(fsFormatPath string, format *formatCacheV1) error {
 // of format cache config
 func initFormatCache(drives []string) (formats []*formatCacheV1, err error) {
 	nformats := newFormatCacheV1(drives)
-	for i, drive := range drives {
-		// Disallow relative paths, figure out absolute paths.
-		cfsPath, err := filepath.Abs(drive)
-		if err != nil {
+	for _, drive := range drives {
+		_, err = os.Stat(drive)
+		if err == nil {
+			continue
+		}
+		if !os.IsNotExist(err) {
 			return nil, err
 		}
-
-		fi, err := os.Stat(cfsPath)
-		if err == nil {
-			if !fi.IsDir() {
-				return nil, syscall.ENOTDIR
-			}
+		if err = os.Mkdir(drive, 0777); err != nil {
+			return nil, err
 		}
-		if os.IsNotExist(err) {
-			// Disk not found create it.
-			err = os.MkdirAll(cfsPath, 0777)
-			if err != nil {
+	}
+	for i, drive := range drives {
+		if err = os.Mkdir(pathJoin(drive, minioMetaBucket), 0777); err != nil {
+			if !os.IsExist(err) {
 				return nil, err
 			}
 		}
-
-		cacheFormatPath := pathJoin(drive, formatConfigFile)
+		cacheFormatPath := pathJoin(drive, minioMetaBucket, formatConfigFile)
 		// Fresh disk - create format.json for this cfs
 		if err = createFormatCache(cacheFormatPath, nformats[i]); err != nil {
 			return nil, err
@@ -146,32 +147,25 @@ func initFormatCache(drives []string) (formats []*formatCacheV1, err error) {
 	return nformats, nil
 }
 
-func loadFormatCache(drives []string) (formats []*formatCacheV1, err error) {
-	var errs []error
-	for _, drive := range drives {
-		cacheFormatPath := pathJoin(drive, formatConfigFile)
-		f, perr := os.Open(cacheFormatPath)
-		if perr != nil {
-			formats = append(formats, nil)
-			errs = append(errs, perr)
-			continue
+func loadFormatCache(drives []string) ([]*formatCacheV1, error) {
+	formats := make([]*formatCacheV1, len(drives))
+	for i, drive := range drives {
+		cacheFormatPath := pathJoin(drive, minioMetaBucket, formatConfigFile)
+		f, err := os.Open(cacheFormatPath)
+		if err != nil {
+			if os.IsNotExist(err) {
+				continue
+			}
+			return nil, err
 		}
 		defer f.Close()
-		format, perr := formatMetaCacheV1(f)
-		if perr != nil {
-			// format could not be unmarshalled.
-			formats = append(formats, nil)
-			errs = append(errs, perr)
+		format, err := formatMetaCacheV1(f)
+		if err != nil {
 			continue
 		}
-		formats = append(formats, format)
+		formats[i] = format
 	}
-	for _, perr := range errs {
-		if perr != nil {
-			err = perr
-		}
-	}
-	return formats, err
+	return formats, nil
 }
 
 // unmarshalls the cache format.json into formatCacheV1
@@ -198,7 +192,6 @@ func checkFormatCacheValue(format *formatCacheV1) error {
 }
 
 func checkFormatCacheValues(formats []*formatCacheV1) (int, error) {
-
 	for i, formatCache := range formats {
 		if formatCache == nil {
 			continue
@@ -276,6 +269,15 @@ func findCacheDiskIndex(disk string, disks []string) int {
 
 // validate whether cache drives order has changed
 func validateCacheFormats(formats []*formatCacheV1) error {
+	count := 0
+	for _, format := range formats {
+		if format == nil {
+			count++
+		}
+	}
+	if count == len(formats) {
+		return errors.New("Cache format files missing on all drives")
+	}
 	if _, err := checkFormatCacheValues(formats); err != nil {
 		return err
 	}
@@ -290,23 +292,9 @@ func validateCacheFormats(formats []*formatCacheV1) error {
 func cacheDrivesUnformatted(drives []string) bool {
 	count := 0
 	for _, drive := range drives {
-		cacheFormatPath := pathJoin(drive, formatConfigFile)
-
-		// // Disallow relative paths, figure out absolute paths.
-		cfsPath, err := filepath.Abs(cacheFormatPath)
-		if err != nil {
-			continue
-		}
-
-		fi, err := os.Stat(cfsPath)
-		if err == nil {
-			if !fi.IsDir() {
-				continue
-			}
-		}
-		if os.IsNotExist(err) {
+		cacheFormatPath := pathJoin(drive, minioMetaBucket, formatConfigFile)
+		if _, err := os.Stat(cacheFormatPath); os.IsNotExist(err) {
 			count++
-			continue
 		}
 	}
 	return count == len(drives)
@@ -322,7 +310,10 @@ func loadAndValidateCacheFormat(drives []string) (formats []*formatCacheV1, err
 		formats, err = loadFormatCache(drives)
 	}
 	if err != nil {
-		return formats, err
+		return nil, err
 	}
-	return formats, validateCacheFormats(formats)
+	if err = validateCacheFormats(formats); err != nil {
+		return nil, err
+	}
+	return formats, nil
 }