Enhance picking valid xlMeta based on quorum (#6297)

This PR borrows the idea from getFormatXLQuorum()

cmd/xl-v1-healing.go

@@ -404,7 +404,7 @@ func healObject(ctx context.Context, storageDisks []StorageAPI, bucket string, o
 
 	// Latest xlMetaV1 for reference. If a valid metadata is not
 	// present, it is as good as object not found.
-	latestMeta, pErr := pickValidXLMeta(ctx, partsMetadata, modTime)
+	latestMeta, pErr := pickValidXLMeta(ctx, partsMetadata, modTime, quorum)
 	if pErr != nil {
 		return result, toObjectErr(pErr, bucket, object)
 	}

cmd/xl-v1-metadata.go

@@ -18,9 +18,9 @@ package cmd
 
 import (
 	"context"
+	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
-	"fmt"
 	"path"
 	"sort"
 	"sync"
@@ -295,18 +295,52 @@ func (m xlMetaV1) ObjectToPartOffset(ctx context.Context, offset int64) (partInd
 	return 0, 0, InvalidRange{}
 }
 
-// pickValidXLMeta - picks one valid xlMeta content and returns from a
-// slice of xlmeta content.
-func pickValidXLMeta(ctx context.Context, metaArr []xlMetaV1, modTime time.Time) (xmv xlMetaV1, e error) {
-	// Pick latest valid metadata.
-	for _, meta := range metaArr {
+func getXLMetaInQuorum(ctx context.Context, metaArr []xlMetaV1, modTime time.Time, quorum int) (xmv xlMetaV1, e error) {
+	metaHashes := make([]string, len(metaArr))
+	for i, meta := range metaArr {
 		if meta.IsValid() && meta.Stat.ModTime.Equal(modTime) {
-			return meta, nil
+			h := sha256.New()
+			for _, p := range meta.Parts {
+				h.Write([]byte(p.Name))
 			}
+			metaHashes[i] = hex.EncodeToString(h.Sum(nil))
 		}
-	err := fmt.Errorf("No valid xl.json present")
-	logger.LogIf(ctx, err)
-	return xmv, err
+	}
+
+	metaHashCountMap := make(map[string]int)
+	for _, hash := range metaHashes {
+		if hash == "" {
+			continue
+		}
+		metaHashCountMap[hash]++
+	}
+
+	maxHash := ""
+	maxCount := 0
+	for hash, count := range metaHashCountMap {
+		if count > maxCount {
+			maxCount = count
+			maxHash = hash
+		}
+	}
+
+	if maxCount < quorum {
+		return xlMetaV1{}, errXLReadQuorum
+	}
+
+	for i, hash := range metaHashes {
+		if hash == maxHash {
+			return metaArr[i], nil
+		}
+	}
+
+	return xlMetaV1{}, errXLReadQuorum
+}
+
+// pickValidXLMeta - picks one valid xlMeta content and returns from a
+// slice of xlmeta content.
+func pickValidXLMeta(ctx context.Context, metaArr []xlMetaV1, modTime time.Time, quorum int) (xmv xlMetaV1, e error) {
+	return getXLMetaInQuorum(ctx, metaArr, modTime, quorum)
 }
 
 // list of all errors that can be ignored in a metadata operation.

cmd/xl-v1-metadata_test.go

@@ -19,7 +19,6 @@ package cmd
 import (
 	"bytes"
 	"context"
-	"errors"
 	"os"
 	"path"
 	"strconv"
@@ -349,11 +348,11 @@ func TestPickValidXLMeta(t *testing.T) {
 			metaArr:     invalidXS,
 			modTime:     now,
 			xlMeta:      invalidX1,
-			expectedErr: errors.New("No valid xl.json present"),
+			expectedErr: errXLReadQuorum,
 		},
 	}
 	for i, test := range testCases {
-		xlMeta, err := pickValidXLMeta(context.Background(), test.metaArr, test.modTime)
+		xlMeta, err := pickValidXLMeta(context.Background(), test.metaArr, test.modTime, len(test.metaArr)/2)
 		if test.expectedErr != nil {
 			if err.Error() != test.expectedErr.Error() {
 				t.Errorf("Test %d: Expected to fail with %v but received %v",

cmd/xl-v1-multipart.go

@@ -346,7 +346,7 @@ func (xl xlObjects) PutObjectPart(ctx context.Context, bucket, object, uploadID
 	onlineDisks, modTime := listOnlineDisks(xl.getDisks(), partsMetadata, errs)
 
 	// Pick one from the first valid metadata.
-	xlMeta, err := pickValidXLMeta(ctx, partsMetadata, modTime)
+	xlMeta, err := pickValidXLMeta(ctx, partsMetadata, modTime, writeQuorum)
 	if err != nil {
 		return pi, err
 	}
@@ -445,7 +445,7 @@ func (xl xlObjects) PutObjectPart(ctx context.Context, bucket, object, uploadID
 	onlineDisks, modTime = listOnlineDisks(onlineDisks, partsMetadata, errs)
 
 	// Pick one from the first valid metadata.
-	xlMeta, err = pickValidXLMeta(ctx, partsMetadata, modTime)
+	xlMeta, err = pickValidXLMeta(ctx, partsMetadata, modTime, writeQuorum)
 	if err != nil {
 		return pi, err
 	}
@@ -645,7 +645,7 @@ func (xl xlObjects) CompleteMultipartUpload(ctx context.Context, bucket string,
 	var objectSize int64
 
 	// Pick one from the first valid metadata.
-	xlMeta, err := pickValidXLMeta(ctx, partsMetadata, modTime)
+	xlMeta, err := pickValidXLMeta(ctx, partsMetadata, modTime, writeQuorum)
 	if err != nil {
 		return oi, err
 	}

cmd/xl-v1-object.go

@@ -102,7 +102,7 @@ func (xl xlObjects) CopyObject(ctx context.Context, srcBucket, srcObject, dstBuc
 	_, modTime := listOnlineDisks(storageDisks, metaArr, errs)
 
 	// Pick latest valid metadata.
-	xlMeta, err := pickValidXLMeta(ctx, metaArr, modTime)
+	xlMeta, err := pickValidXLMeta(ctx, metaArr, modTime, readQuorum)
 	if err != nil {
 		return oi, toObjectErr(err, srcBucket, srcObject)
 	}
@@ -221,7 +221,7 @@ func (xl xlObjects) getObject(ctx context.Context, bucket, object string, startO
 	onlineDisks, modTime := listOnlineDisks(xl.getDisks(), metaArr, errs)
 
 	// Pick latest valid metadata.
-	xlMeta, err := pickValidXLMeta(ctx, metaArr, modTime)
+	xlMeta, err := pickValidXLMeta(ctx, metaArr, modTime, readQuorum)
 	if err != nil {
 		return err
 	}
@@ -402,7 +402,7 @@ func (xl xlObjects) getObjectInfo(ctx context.Context, bucket, object string) (o
 	modTime, _ := commonTime(modTimes)
 
 	// Pick latest valid metadata.
-	xlMeta, err := pickValidXLMeta(ctx, metaArr, modTime)
+	xlMeta, err := pickValidXLMeta(ctx, metaArr, modTime, readQuorum)
 	if err != nil {
 		return objInfo, err
 	}