xl: Handle read quorum for StatVol, ListVols

bucket-handlers.go

@@ -348,7 +348,13 @@ func (api objectAPIHandlers) ListBucketsHandler(w http.ResponseWriter, r *http.R
 		return
 	}
 	errorIf(err.Trace(), "ListBuckets failed.", nil)
-	writeErrorResponse(w, r, ErrInternalError, r.URL.Path)
+	switch err.ToGoError().(type) {
+	case StorageInsufficientReadResources:
+		writeErrorResponse(w, r, ErrInsufficientReadResources, r.URL.Path)
+	default:
+		writeErrorResponse(w, r, ErrInternalError, r.URL.Path)
+	}
+
 }
 
 // DeleteMultipleObjectsHandler - deletes multiple objects.
@@ -628,6 +634,8 @@ func (api objectAPIHandlers) HeadBucketHandler(w http.ResponseWriter, r *http.Re
 			writeErrorResponse(w, r, ErrNoSuchBucket, r.URL.Path)
 		case BucketNameInvalid:
 			writeErrorResponse(w, r, ErrInvalidBucketName, r.URL.Path)
+		case StorageInsufficientReadResources:
+			writeErrorResponse(w, r, ErrInsufficientReadResources, r.URL.Path)
 		default:
 			writeErrorResponse(w, r, ErrInternalError, r.URL.Path)
 		}

fs.go

@@ -132,25 +132,24 @@ func checkDiskFree(diskPath string, minFreeDisk int64) (err error) {
 	return nil
 }
 
-// removeDuplicateVols - remove duplicate volumes.
-func removeDuplicateVols(vols []VolInfo) []VolInfo {
-	length := len(vols) - 1
-	for i := 0; i < length; i++ {
-		for j := i + 1; j <= length; j++ {
-			if vols[i].Name == vols[j].Name {
-				// Pick the latest volume, if there is a duplicate.
-				if vols[i].Created.Sub(vols[j].Created) > 0 {
-					vols[i] = vols[length]
-				} else {
-					vols[j] = vols[length]
-				}
-				vols = vols[0:length]
-				length--
-				j--
-			}
+func removeDuplicateVols(volsInfo []VolInfo) []VolInfo {
+	// Use map to record duplicates as we find them.
+	result := []VolInfo{}
+
+	m := make(map[string]VolInfo)
+	for _, v := range volsInfo {
+		if _, found := m[v.Name]; !found {
+			m[v.Name] = v
 		}
 	}
-	return vols
+
+	result = make([]VolInfo, 0, len(m))
+	for _, v := range m {
+		result = append(result, v)
+	}
+
+	// Return the new slice.
+	return result
 }
 
 // gets all the unique directories from diskPath.
@@ -184,8 +183,7 @@ func getAllUniqueVols(dirPath string) ([]VolInfo, error) {
 			Created: fi.ModTime(),
 		})
 	}
-	volsInfo = removeDuplicateVols(volsInfo)
-	return volsInfo, nil
+	return removeDuplicateVols(volsInfo), nil
 }
 
 // getVolumeDir - will convert incoming volume names to

object-api.go

@@ -22,6 +22,7 @@ import (
 	"errors"
 	"io"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"github.com/minio/minio/pkg/mimedb"
@@ -78,6 +79,13 @@ func (o objectAPI) GetBucketInfo(bucket string) (BucketInfo, *probe.Error) {
 	}, nil
 }
 
+// byBucketName is a collection satisfying sort.Interface.
+type byBucketName []BucketInfo
+
+func (d byBucketName) Len() int           { return len(d) }
+func (d byBucketName) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
+func (d byBucketName) Less(i, j int) bool { return d[i].Name < d[j].Name }
+
 // ListBuckets - list buckets.
 func (o objectAPI) ListBuckets() ([]BucketInfo, *probe.Error) {
 	var bucketInfos []BucketInfo
@@ -98,6 +106,7 @@ func (o objectAPI) ListBuckets() ([]BucketInfo, *probe.Error) {
 			Free:    vol.Free,
 		})
 	}
+	sort.Sort(byBucketName(bucketInfos))
 	return bucketInfos, nil
 }
 

xl-v1.go

@@ -172,6 +172,10 @@ func (xl XL) MakeVol(volume string) error {
 	// Make a volume entry on all underlying storage disks.
 	for _, disk := range xl.storageDisks {
 		if err := disk.MakeVol(volume); err != nil {
+			// We ignore error if errVolumeExists and creating a volume again.
+			if err == errVolumeExists {
+				continue
+			}
 			return err
 		}
 	}
@@ -185,6 +189,10 @@ func (xl XL) DeleteVol(volume string) error {
 	}
 	for _, disk := range xl.storageDisks {
 		if err := disk.DeleteVol(volume); err != nil {
+			// We ignore error if errVolumeNotFound.
+			if err == errVolumeNotFound {
+				continue
+			}
 			return err
 		}
 	}
@@ -193,13 +201,40 @@ func (xl XL) DeleteVol(volume string) error {
 
 // ListVols - list volumes.
 func (xl XL) ListVols() (volsInfo []VolInfo, err error) {
-	// Pick the first node and list there always.
-	disk := xl.storageDisks[0]
-	volsInfo, err = disk.ListVols()
-	if err == nil {
-		return volsInfo, nil
+	emptyCount := 0
+	// Success vols map carries successful results of ListVols from
+	// each disks.
+	var successVolsMap = make(map[int][]VolInfo)
+	for index, disk := range xl.storageDisks {
+		var vlsInfo []VolInfo
+		vlsInfo, err = disk.ListVols()
+		if err == nil {
+			if len(vlsInfo) == 0 {
+				emptyCount++
+			} else {
+				successVolsMap[index] = vlsInfo
+			}
+		}
 	}
-	return nil, err
+
+	// If all list operations resulted in an empty count which is same
+	// as your total storage disks, then it is a valid case return
+	// success with empty vols.
+	if emptyCount == len(xl.storageDisks) {
+		return []VolInfo{}, nil
+	} else if len(successVolsMap) < xl.readQuorum {
+		// If there is data and not empty, then we attempt quorum verification.
+		// Verify if we have enough quorum to list vols.
+		return nil, errReadQuorum
+	}
+	// Loop through success vols map and return the first value.
+	for index := range xl.storageDisks {
+		if _, ok := successVolsMap[index]; ok {
+			volsInfo = successVolsMap[index]
+			break
+		}
+	}
+	return volsInfo, nil
 }
 
 // StatVol - get volume stat info.
@@ -207,13 +242,33 @@ func (xl XL) StatVol(volume string) (volInfo VolInfo, err error) {
 	if !isValidVolname(volume) {
 		return VolInfo{}, errInvalidArgument
 	}
-	// Pick the first node and list there always.
-	disk := xl.storageDisks[0]
-	volInfo, err = disk.StatVol(volume)
-	if err == nil {
-		return volInfo, nil
+	var statVols []VolInfo
+	volumeNotFoundErrCnt := 0
+	for _, disk := range xl.storageDisks {
+		volInfo, err = disk.StatVol(volume)
+		if err == nil {
+			// Collect all the successful attempts to verify quorum
+			// subsequently.
+			statVols = append(statVols, volInfo)
+		} else if err == errVolumeNotFound {
+			// Count total amount of volume not found errors.
+			volumeNotFoundErrCnt++
+		}
 	}
-	return VolInfo{}, err
+
+	// If volume not found err count is same as total storage disks, we
+	// really don't have the bucket, report a valid error.
+	if volumeNotFoundErrCnt == len(xl.storageDisks) {
+		return VolInfo{}, errVolumeNotFound
+	} else if len(statVols) < xl.readQuorum {
+		// If one of the disks have bucket we need to validate if we
+		// have read quorum, if not fail.
+		return VolInfo{}, errReadQuorum
+	}
+
+	// If successful remove all the duplicates and keep the latest one.
+	volInfo = removeDuplicateVols(statVols)[0]
+	return volInfo, nil
 }
 
 // isLeafDirectory - check if a given path is leaf directory. i.e