xl: Simplify reading metadata and add a new fileMetadata type. (#1346)

xl-v1-createfile.go

@@ -79,7 +79,7 @@ func (xl XL) getFileQuorumVersionMap(volume, path string) map[int]int64 {
 	metadataFilePath := slashpath.Join(path, metadataFile)
 	// Set offset to 0 to read entire file.
 	offset := int64(0)
-	metadata := make(map[string]string)
+	metadata := make(fileMetadata)
 
 	// Allocate disk index format map - do not use maps directly
 	// without allocating.
@@ -94,21 +94,20 @@ func (xl XL) getFileQuorumVersionMap(volume, path string) map[int]int64 {
 		metadataReader, err := disk.ReadFile(volume, metadataFilePath, offset)
 		if err != nil {
 			continue
-
 		} else if err = json.NewDecoder(metadataReader).Decode(&metadata); err != nil {
 			continue
-
-		} else if _, ok := metadata["file.version"]; !ok {
-			fileQuorumVersionMap[index] = 0
-
 		}
-		// Convert string to integer.
-		fileVersion, err := strconv.ParseInt(metadata["file.version"], 10, 64)
-		if err != nil {
-			continue
 
+		if version := metadata.Get("file.version"); version == nil {
+			fileQuorumVersionMap[index] = 0
+		} else {
+			// Convert string to integer.
+			fileVersion, err := strconv.ParseInt(version[0], 10, 64)
+			if err != nil {
+				continue
+			}
+			fileQuorumVersionMap[index] = fileVersion
 		}
-		fileQuorumVersionMap[index] = fileVersion
 	}
 	return fileQuorumVersionMap
 }
@@ -238,21 +237,21 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
 	}
 
 	// Initialize metadata map, save all erasure related metadata.
-	metadata := make(map[string]string)
-	metadata["version"] = minioVersion
-	metadata["format.major"] = "1"
-	metadata["format.minor"] = "0"
-	metadata["format.patch"] = "0"
-	metadata["file.size"] = strconv.FormatInt(totalSize, 10)
+	metadata := make(fileMetadata)
+	metadata.Set("version", minioVersion)
+	metadata.Set("format.major", "1")
+	metadata.Set("format.minor", "0")
+	metadata.Set("format.patch", "0")
+	metadata.Set("file.size", strconv.FormatInt(totalSize, 10))
 	if len(xl.storageDisks) > len(writers) {
 		// Save file.version only if we wrote to less disks than all
 		// storage disks.
-		metadata["file.version"] = strconv.FormatInt(higherVersion, 10)
+		metadata.Set("file.version", strconv.FormatInt(higherVersion, 10))
 	}
-	metadata["file.modTime"] = modTime.Format(timeFormatAMZ)
-	metadata["file.xl.blockSize"] = strconv.Itoa(erasureBlockSize)
-	metadata["file.xl.dataBlocks"] = strconv.Itoa(xl.DataBlocks)
-	metadata["file.xl.parityBlocks"] = strconv.Itoa(xl.ParityBlocks)
+	metadata.Set("file.modTime", modTime.Format(timeFormatAMZ))
+	metadata.Set("file.xl.blockSize", strconv.Itoa(erasureBlockSize))
+	metadata.Set("file.xl.dataBlocks", strconv.Itoa(xl.DataBlocks))
+	metadata.Set("file.xl.parityBlocks", strconv.Itoa(xl.ParityBlocks))
 
 	// Write all the metadata.
 	// below case is not handled here
@@ -265,25 +264,17 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
 		}
 		if sha512Writers[index] != nil {
 			// Save sha512 checksum of each encoded blocks.
-			metadata["file.xl.block512Sum"] = hex.EncodeToString(sha512Writers[index].Sum(nil))
+			metadata.Set("file.xl.block512Sum", hex.EncodeToString(sha512Writers[index].Sum(nil)))
 		}
 
-		// Marshal metadata into json strings.
-		metadataBytes, err := json.Marshal(metadata)
+		// Write metadata.
+		err := metadata.Write(metadataWriter)
 		if err != nil {
 			// Remove temporary files.
 			xl.cleanupCreateFileOps(volume, path, append(writers, metadataWriters...)...)
 			reader.CloseWithError(err)
 			return
 		}
-
-		// Write metadata to disk.
-		_, err = metadataWriter.Write(metadataBytes)
-		if err != nil {
-			xl.cleanupCreateFileOps(volume, path, append(writers, metadataWriters...)...)
-			reader.CloseWithError(err)
-			return
-		}
 	}
 
 	// Close all writers and metadata writers in routines.

xl-v1-errors.go

@@ -0,0 +1,31 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package main
+
+import "errors"
+
+// errFileSize - returned for missing file size.
+var errFileSize = errors.New("Missing 'file.size' in metadata")
+
+// errMaxDisks - returned for reached maximum of disks.
+var errMaxDisks = errors.New("Total number of disks specified is higher than supported maximum of '16'")
+
+// errNumDisks - returned for odd numebr of disks.
+var errNumDisks = errors.New("Invalid number of disks provided, should be always multiples of '2'")
+
+// errModTime - returned for missing file modtime.
+var errModTime = errors.New("Missing 'file.modTime' in metadata")

xl-v1-metadata.go

@@ -0,0 +1,78 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package main
+
+import (
+	"encoding/json"
+	"io"
+)
+
+// This code is built on similar ideas of http.Header.
+// Ref - https://golang.org/pkg/net/http/#Header
+
+// A fileMetadata represents a metadata header mapping
+// keys to sets of values.
+type fileMetadata map[string][]string
+
+// Add adds the key, value pair to the header.
+// It appends to any existing values associated with key.
+func (f fileMetadata) Add(key, value string) {
+	f[key] = append(f[key], value)
+}
+
+// Set sets the header entries associated with key to
+// the single element value. It replaces any existing
+// values associated with key.
+func (f fileMetadata) Set(key, value string) {
+	f[key] = []string{value}
+}
+
+// Get gets the first value associated with the given key.
+// If there are no values associated with the key, Get returns "".
+// Get is a convenience method.  For more complex queries,
+// access the map directly.
+func (f fileMetadata) Get(key string) []string {
+	if f == nil {
+		return nil
+	}
+	v, ok := f[key]
+	if !ok {
+		return nil
+	}
+	return v
+}
+
+// Write writes a metadata in wire format.
+func (f fileMetadata) Write(writer io.Writer) error {
+	metadataBytes, err := json.Marshal(f)
+	if err != nil {
+		return err
+	}
+	_, err = writer.Write(metadataBytes)
+	return err
+}
+
+// fileMetadataDecode - file metadata decode.
+func fileMetadataDecode(reader io.Reader) (fileMetadata, error) {
+	metadata := make(fileMetadata)
+	decoder := json.NewDecoder(reader)
+	// Unmarshalling failed, file possibly corrupted.
+	if err := decoder.Decode(&metadata); err != nil {
+		return nil, err
+	}
+	return metadata, nil
+}

xl-v1-readfile.go

@@ -55,9 +55,9 @@ func (xl XL) getReadableDisks(volume, path string) ([]StorageAPI, int64, error)
 	fileSize := int64(0)
 	for index, metadata := range partsMetadata {
 		if errs[index] == nil {
-			if versionStr, ok := metadata["file.version"]; ok {
+			if version := metadata.Get("file.version"); version != nil {
 				// Convert string to integer.
-				version, err := strconv.ParseInt(versionStr, 10, 64)
+				version, err := strconv.ParseInt(version[0], 10, 64)
 				if err != nil {
 					// Unexpected, return error.
 					return nil, 0, err
@@ -91,15 +91,15 @@ func (xl XL) getReadableDisks(volume, path string) ([]StorageAPI, int64, error)
 		if disk == nil {
 			continue
 		}
-		if sizeStr, ok := partsMetadata[index]["file.size"]; ok {
+		if size := partsMetadata[index].Get("file.size"); size != nil {
 			var err error
-			fileSize, err = strconv.ParseInt(sizeStr, 10, 64)
+			fileSize, err = strconv.ParseInt(size[0], 10, 64)
 			if err != nil {
 				return nil, 0, err
 			}
 			break
 		} else {
-			return nil, 0, errors.New("Missing 'file.size' in meta data.")
+			return nil, 0, errFileSize
 		}
 	}
 	return quorumDisks, fileSize, nil

xl-v1-utils.go

@@ -9,12 +9,11 @@ import (
 
 // Get parts.json metadata as a map slice.
 // Returns error slice indicating the failed metadata reads.
-func (xl XL) getPartsMetadata(volume, path string) ([]map[string]string, []error) {
+func (xl XL) getPartsMetadata(volume, path string) ([]fileMetadata, []error) {
 	errs := make([]error, len(xl.storageDisks))
-	metadataArray := make([]map[string]string, len(xl.storageDisks))
+	metadataArray := make([]fileMetadata, len(xl.storageDisks))
 	metadataFilePath := slashpath.Join(path, metadataFile)
 	for index, disk := range xl.storageDisks {
-		metadata := make(map[string]string)
 		offset := int64(0)
 		metadataReader, err := disk.ReadFile(volume, metadataFilePath, offset)
 		if err != nil {
@@ -23,8 +22,8 @@ func (xl XL) getPartsMetadata(volume, path string) ([]map[string]string, []error
 		}
 		defer metadataReader.Close()
 
-		decoder := json.NewDecoder(metadataReader)
-		if err = decoder.Decode(&metadata); err != nil {
+		metadata, err := fileMetadataDecode(metadataReader)
+		if err != nil {
 			// Unable to parse parts.json, set error.
 			errs[index] = err
 			continue
@@ -39,12 +38,12 @@ func (xl XL) getPartsMetadata(volume, path string) ([]map[string]string, []error
 //
 // Returns collection of errors, indexed in accordance with input
 // updateParts order.
-func (xl XL) setPartsMetadata(volume, path string, metadata map[string]string, updateParts []bool) []error {
+func (xl XL) setPartsMetadata(volume, path string, metadata fileMetadata, updateParts []bool) []error {
 	metadataFilePath := filepath.Join(path, metadataFile)
 	errs := make([]error, len(xl.storageDisks))
 
 	for index := range updateParts {
-		errs[index] = errors.New("metadata not updated")
+		errs[index] = errors.New("Metadata not updated")
 	}
 
 	metadataBytes, err := json.Marshal(metadata)

xl-v1.go

@@ -17,9 +17,6 @@
 package main
 
 import (
-	"encoding/hex"
-	"encoding/json"
-	"errors"
 	"fmt"
 	"os"
 	slashpath "path"
@@ -102,7 +99,7 @@ func newXL(disks ...string) (StorageAPI, error) {
 	// Verify disks.
 	totalDisks := len(disks)
 	if totalDisks > maxErasureBlocks {
-		return nil, errors.New("Total number of disks specified is higher than supported maximum of '16'")
+		return nil, errMaxDisks
 	}
 
 	// isEven function to verify if a given number if even.
@@ -112,7 +109,7 @@ func newXL(disks ...string) (StorageAPI, error) {
 
 	// TODO: verify if this makes sense in future.
 	if !isEven(totalDisks) {
-		return nil, errors.New("Invalid number of directories provided, should be always multiples of '2'")
+		return nil, errNumDisks
 	}
 
 	// Calculate data and parity blocks.
@@ -125,9 +122,9 @@ func newXL(disks ...string) (StorageAPI, error) {
 	}
 
 	// Save the reedsolomon.
-	xl.ReedSolomon = rs
 	xl.DataBlocks = dataBlocks
 	xl.ParityBlocks = parityBlocks
+	xl.ReedSolomon = rs
 
 	// Initialize all storage disks.
 	storageDisks := make([]StorageAPI, len(disks))
@@ -150,6 +147,7 @@ func newXL(disks ...string) (StorageAPI, error) {
 	// Read quorum should be always N/2 + 1 (due to Vandermonde matrix
 	// erasure requirements)
 	xl.readQuorum = len(xl.storageDisks)/2 + 1
+
 	// Write quorum is assumed if we have total disks + 3
 	// parity. (Need to discuss this again)
 	xl.writeQuorum = len(xl.storageDisks)/2 + 3
@@ -302,16 +300,21 @@ func (xl XL) isLeafDirectory(volume, leafPath string) (isLeaf bool) {
 	return isLeaf
 }
 
-// fileMetadata - file metadata is a structured representation of the
-// unmarshalled metadata file.
-type fileMetadata struct {
-	Size         int64
-	ModTime      time.Time
-	BlockSize    int64
-	Block512Sum  string
-	DataBlocks   int
-	ParityBlocks int
-	fileVersion  int64
+// Returns file size from the metadata.
+func getFileSize(metadata fileMetadata) (int64, error) {
+	size := metadata.Get("file.size")
+	if size == nil {
+		return 0, errFileSize
+	}
+	return strconv.ParseInt(size[0], 10, 64)
+}
+
+func getModTime(metadata fileMetadata) (time.Time, error) {
+	modTime := metadata.Get("file.modTime")
+	if modTime == nil {
+		return time.Time{}, errModTime
+	}
+	return time.Parse(timeFormatAMZ, modTime[0])
 }
 
 // extractMetadata - extract file metadata.
@@ -323,83 +326,40 @@ func (xl XL) extractMetadata(volume, path string) (fileMetadata, error) {
 	disk := xl.storageDisks[0]
 	metadataReader, err := disk.ReadFile(volume, metadataFilePath, offset)
 	if err != nil {
-		return fileMetadata{}, err
+		return nil, err
 	}
 	// Close metadata reader.
 	defer metadataReader.Close()
 
-	var metadata = make(map[string]string)
-	decoder := json.NewDecoder(metadataReader)
-	// Unmarshalling failed, file possibly corrupted.
-	if err = decoder.Decode(&metadata); err != nil {
-		return fileMetadata{}, err
-	}
-	modTime, err := time.Parse(timeFormatAMZ, metadata["file.modTime"])
+	metadata, err := fileMetadataDecode(metadataReader)
 	if err != nil {
-		return fileMetadata{}, err
-	}
-
-	// Verify if size is parsable.
-	var size int64
-	size, err = strconv.ParseInt(metadata["file.size"], 10, 64)
-	if err != nil {
-		return fileMetadata{}, err
+		return nil, err
 	}
+	return metadata, nil
+}
 
-	// Verify if file.version is parsable.
-	var fileVersion int64
-	// missing file.version is valid
-	if _, ok := metadata["file.version"]; ok {
-		fileVersion, err = strconv.ParseInt(metadata["file.version"], 10, 64)
-		if err != nil {
-			return fileMetadata{}, err
-		}
-	}
+// Extract file info from paths.
+func (xl XL) extractFileInfo(volume, path string) (FileInfo, error) {
+	fileInfo := FileInfo{}
+	fileInfo.Volume = volume
+	fileInfo.Name = path
 
-	// Verify if block size is parsable.
-	var blockSize int64
-	blockSize, err = strconv.ParseInt(metadata["file.xl.blockSize"], 10, 64)
+	metadata, err := xl.extractMetadata(volume, path)
 	if err != nil {
-		return fileMetadata{}, err
+		return FileInfo{}, err
 	}
-
-	// Verify if data blocks and parity blocks are parsable.
-	var dataBlocks, parityBlocks int
-	dataBlocks, err = strconv.Atoi(metadata["file.xl.dataBlocks"])
+	fileSize, err := getFileSize(metadata)
 	if err != nil {
-		return fileMetadata{}, err
+		return FileInfo{}, err
 	}
-	parityBlocks, err = strconv.Atoi(metadata["file.xl.parityBlocks"])
+	fileModTime, err := getModTime(metadata)
 	if err != nil {
-		return fileMetadata{}, err
+		return FileInfo{}, err
 	}
-
-	// Verify if sha512sum is of proper hex format.
-	sha512Sum := metadata["file.xl.block512Sum"]
-	_, err = hex.DecodeString(sha512Sum)
-	if err != nil {
-		return fileMetadata{}, err
-	}
-
-	// Return the concocted metadata.
-	return fileMetadata{
-		Size:         size,
-		ModTime:      modTime,
-		BlockSize:    blockSize,
-		Block512Sum:  sha512Sum,
-		DataBlocks:   dataBlocks,
-		ParityBlocks: parityBlocks,
-		fileVersion:  fileVersion,
-	}, nil
-}
-
-const (
-	slashSeparator = "/"
-)
-
-// retainSlash - retains slash from a path.
-func retainSlash(path string) string {
-	return strings.TrimSuffix(path, slashSeparator) + slashSeparator
+	fileInfo.Size = fileSize
+	fileInfo.Mode = os.FileMode(0644)
+	fileInfo.ModTime = fileModTime
+	return fileInfo, nil
 }
 
 // byFileInfoName is a collection satisfying sort.Interface.
@@ -427,21 +387,6 @@ func (xl XL) ListFiles(volume, prefix, marker string, recursive bool, count int)
 		}
 	}
 
-	// Extract file info from paths.
-	extractFileInfo := func(volume, path string) (FileInfo, error) {
-		var fileInfo = FileInfo{}
-		var metadata fileMetadata
-		fileInfo.Name = slashpath.Dir(path)
-		metadata, err = xl.extractMetadata(volume, fileInfo.Name)
-		if err != nil {
-			return FileInfo{}, err
-		}
-		fileInfo.Size = metadata.Size
-		fileInfo.ModTime = metadata.ModTime
-		fileInfo.Mode = os.FileMode(0644)
-		return fileInfo, nil
-	}
-
 	// List files.
 	fsFilesInfo, eof, err = disk.ListFiles(volume, prefix, markerPath, recursive, count)
 	if err != nil {
@@ -459,7 +404,10 @@ func (xl XL) ListFiles(volume, prefix, marker string, recursive bool, count int)
 			isLeaf = xl.isLeafDirectory(volume, fsFileInfo.Name)
 		}
 		if isLeaf || !fsFileInfo.Mode.IsDir() {
-			fileInfo, err = extractFileInfo(volume, fsFileInfo.Name)
+			// Extract the parent of leaf directory or file to get the
+			// actual name.
+			path := slashpath.Dir(fsFileInfo.Name)
+			fileInfo, err = xl.extractFileInfo(volume, path)
 			if err != nil {
 				// For a leaf directory, if err is FileNotFound then
 				// perhaps has a missing metadata. Ignore it and let
@@ -491,19 +439,13 @@ func (xl XL) StatFile(volume, path string) (FileInfo, error) {
 	}
 
 	// Extract metadata.
-	metadata, err := xl.extractMetadata(volume, path)
+	fileInfo, err := xl.extractFileInfo(volume, path)
 	if err != nil {
 		return FileInfo{}, err
 	}
 
-	// Return file info.
-	return FileInfo{
-		Volume:  volume,
-		Name:    path,
-		Size:    metadata.Size,
-		ModTime: metadata.ModTime,
-		Mode:    os.FileMode(0644),
-	}, nil
+	// Return fileinfo.
+	return fileInfo, nil
 }
 
 // DeleteFile - delete a file