xl: add quorum support for create file

xl-v1-createfile.go

@@ -51,34 +51,67 @@ func closeAndRemoveWriters(writers ...io.WriteCloser) {
 // WriteErasure reads predefined blocks, encodes them and writes to
 // configured storage disks.
 func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
-	var writers = make([]io.WriteCloser, len(xl.storageDisks))
-	var sha512Writers = make([]hash.Hash, len(xl.storageDisks))
-	var metadataWriters = make([]io.WriteCloser, len(xl.storageDisks))
+	xl.lockNS(volume, path, false)
+	defer xl.unlockNS(volume, path, false)
+
+	// get available quorum for existing file path
+	_, higherVersion := xl.getQuorumDisks(volume, path)
+	// increment to have next higher version
+	higherVersion++
+
+	quorumDisks := make([]quorumDisk, len(xl.storageDisks))
+	writers := make([]io.WriteCloser, len(xl.storageDisks))
+	sha512Writers := make([]hash.Hash, len(xl.storageDisks))
+
+	metadataFilePath := slashpath.Join(path, metadataFile)
+	metadataWriters := make([]io.WriteCloser, len(xl.storageDisks))
 
 	// Save additional erasureMetadata.
 	modTime := time.Now().UTC()
 
-	// Initialize storage disks, get all the writers and corresponding
-	// metadata writers.
+	createFileError := 0
+	maxIndex := 0
 	for index, disk := range xl.storageDisks {
-		var err error
 		erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
-		writers[index], err = disk.CreateFile(volume, erasurePart)
+		writer, err := disk.CreateFile(volume, erasurePart)
 		if err != nil {
+			createFileError++
+
+			// we can safely allow CreateFile errors up to len(xl.storageDisks) - xl.writeQuorum
+			// otherwise return failure
+			if createFileError <= len(xl.storageDisks)-xl.writeQuorum {
+				continue
+			}
+
 			// Remove previous temp writers for any failure.
 			xl.cleanupCreateFileOps(volume, path, append(writers, metadataWriters...)...)
 			reader.CloseWithError(err)
 			return
 		}
-		metadataFilePath := slashpath.Join(path, metadataFile)
-		metadataWriters[index], err = disk.CreateFile(volume, metadataFilePath)
+
+		// create meta data file
+		var metadataWriter io.WriteCloser
+		metadataWriter, err = disk.CreateFile(volume, metadataFilePath)
 		if err != nil {
+			createFileError++
+
+			// we can safely allow CreateFile errors up to len(xl.storageDisks) - xl.writeQuorum
+			// otherwise return failure
+			if createFileError <= len(xl.storageDisks)-xl.writeQuorum {
+				continue
+			}
+
 			// Remove previous temp writers for any failure.
 			xl.cleanupCreateFileOps(volume, path, append(writers, metadataWriters...)...)
 			reader.CloseWithError(err)
 			return
 		}
-		sha512Writers[index] = fastSha512.New()
+
+		writers[maxIndex] = writer
+		metadataWriters[maxIndex] = metadataWriter
+		sha512Writers[maxIndex] = fastSha512.New()
+		quorumDisks[maxIndex] = quorumDisk{disk, index}
+		maxIndex++
 	}
 
 	// Allocate 4MiB block size buffer for reading.
@@ -118,16 +151,19 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
 				reader.CloseWithError(err)
 				return
 			}
-			// Loop through and write encoded data to all the disks.
-			for index, encodedData := range blocks {
-				_, err = writers[index].Write(encodedData)
+
+			// Loop through and write encoded data to quorum disks.
+			for i := 0; i < maxIndex; i++ {
+				encodedData := blocks[quorumDisks[i].index]
+
+				_, err = writers[i].Write(encodedData)
 				if err != nil {
 					// Remove all temp writers upon error.
 					xl.cleanupCreateFileOps(volume, path, append(writers, metadataWriters...)...)
 					reader.CloseWithError(err)
 					return
 				}
-				sha512Writers[index].Write(encodedData)
+				sha512Writers[i].Write(encodedData)
 			}
 			// Update total written.
 			totalSize += int64(n)
@@ -141,15 +177,23 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
 	metadata["format.minor"] = "0"
 	metadata["format.patch"] = "0"
 	metadata["file.size"] = strconv.FormatInt(totalSize, 10)
+	if len(xl.storageDisks) > len(writers) {
+		// save file.version only if we wrote to less disks than all disks
+		metadata["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)
 
 	// Write all the metadata.
-	for index, metadataWriter := range metadataWriters {
+	// below case is not handled here
+	// Case: when storageDisks is 16 and write quorumDisks is 13,
+	//       meta data write failure up to 2 can be considered.
+	//       currently we fail for any meta data writes
+	for i := 0; i < maxIndex; i++ {
 		// Save sha512 checksum of each encoded blocks.
-		metadata["file.xl.block512Sum"] = hex.EncodeToString(sha512Writers[index].Sum(nil))
+		metadata["file.xl.block512Sum"] = hex.EncodeToString(sha512Writers[i].Sum(nil))
 
 		// Marshal metadata into json strings.
 		metadataBytes, err := json.Marshal(metadata)
@@ -161,7 +205,7 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
 		}
 
 		// Write metadata to disk.
-		_, err = metadataWriter.Write(metadataBytes)
+		_, err = metadataWriters[i].Write(metadataBytes)
 		if err != nil {
 			xl.cleanupCreateFileOps(volume, path, append(writers, metadataWriters...)...)
 			reader.CloseWithError(err)
@@ -170,10 +214,10 @@ func (xl XL) writeErasure(volume, path string, reader *io.PipeReader) {
 	}
 
 	// Close all writers and metadata writers in routines.
-	for index := range xl.storageDisks {
+	for i := 0; i < maxIndex; i++ {
 		// Safely wrote, now rename to its actual location.
-		writers[index].Close()
-		metadataWriters[index].Close()
+		writers[i].Close()
+		metadataWriters[i].Close()
 	}
 
 	// Close the pipe reader and return.

xl-v1-readfile.go

@@ -82,10 +82,9 @@ type quorumDisk struct {
 	index int
 }
 
-// getReadFileQuorumDisks - get the current quorum disks.
-func (xl XL) getReadFileQuorumDisks(volume, path string) (quorumDisks []quorumDisk) {
+// getQuorumDisks - get the current quorum disks.
+func (xl XL) getQuorumDisks(volume, path string) (quorumDisks []quorumDisk, higherVersion int64) {
 	diskVersionMap := xl.getMetaFileVersionMap(volume, path)
-	higherVersion := int64(0)
 	for diskIndex, formatVersion := range diskVersionMap {
 		if formatVersion > higherVersion {
 			higherVersion = formatVersion
@@ -142,7 +141,7 @@ func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error)
 	defer xl.unlockNS(volume, path, readLock)
 
 	// Check read quorum.
-	quorumDisks := xl.getReadFileQuorumDisks(volume, path)
+	quorumDisks, _ := xl.getQuorumDisks(volume, path)
 	if len(quorumDisks) < xl.readQuorum {
 		return nil, errReadQuorum
 	}