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minio/xl-v1-readfile.go

240 lines
6.2 KiB

/*
* 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"
"fmt"
"io"
slashpath "path"
"strconv"
)
// checkBlockSize return the size of a single block.
// The first non-zero size is returned,
// or 0 if all blocks are size 0.
func checkBlockSize(blocks [][]byte) int {
for _, block := range blocks {
if len(block) != 0 {
return len(block)
}
}
return 0
}
// calculate the blockSize based on input length and total number of
// data blocks.
func getEncodedBlockLen(inputLen, dataBlocks int) (curBlockSize int) {
curBlockSize = (inputLen + dataBlocks - 1) / dataBlocks
return
}
// Returns slice of disks needed for ReadFile operation:
// - slice returing readable disks.
// - file size
// - error if any.
func (xl XL) getReadableDisks(volume, path string) ([]StorageAPI, int64, error) {
partsMetadata, errs := xl.getPartsMetadata(volume, path)
highestVersion := int64(0)
versions := make([]int64, len(xl.storageDisks))
quorumDisks := make([]StorageAPI, len(xl.storageDisks))
fileSize := int64(0)
for index, metadata := range partsMetadata {
if errs[index] == nil {
if versionStr, ok := metadata["file.version"]; ok {
// Convert string to integer.
version, err := strconv.ParseInt(versionStr, 10, 64)
if err != nil {
// Unexpected, return error.
return nil, 0, err
}
if version > highestVersion {
highestVersion = version
}
versions[index] = version
} else {
versions[index] = 0
}
} else {
versions[index] = -1
}
}
quorumCount := 0
for index, version := range versions {
if version == highestVersion {
quorumDisks[index] = xl.storageDisks[index]
quorumCount++
} else {
quorumDisks[index] = nil
}
}
if quorumCount < xl.readQuorum {
return nil, 0, errReadQuorum
}
for index, disk := range quorumDisks {
if disk == nil {
continue
}
if sizeStr, ok := partsMetadata[index]["file.size"]; ok {
var err error
fileSize, err = strconv.ParseInt(sizeStr, 10, 64)
if err != nil {
return nil, 0, err
}
break
} else {
return nil, 0, errors.New("Missing 'file.size' in meta data.")
}
}
return quorumDisks, fileSize, nil
}
// ReadFile - read file
func (xl XL) ReadFile(volume, path string, offset int64) (io.ReadCloser, error) {
// Input validation.
if !isValidVolname(volume) {
return nil, errInvalidArgument
}
if !isValidPath(path) {
return nil, errInvalidArgument
}
// Acquire a read lock.
readLock := true
xl.lockNS(volume, path, readLock)
defer xl.unlockNS(volume, path, readLock)
quorumDisks, fileSize, err := xl.getReadableDisks(volume, path)
if err != nil {
return nil, err
}
readers := make([]io.ReadCloser, len(xl.storageDisks))
for index, disk := range quorumDisks {
if disk == nil {
continue
}
erasurePart := slashpath.Join(path, fmt.Sprintf("part.%d", index))
// If disk.ReadFile returns error and we don't have read quorum it will be taken care as
// ReedSolomon.Reconstruct() will fail later.
var reader io.ReadCloser
if reader, err = disk.ReadFile(volume, erasurePart, offset); err == nil {
readers[index] = reader
}
}
// Initialize pipe.
pipeReader, pipeWriter := io.Pipe()
go func() {
var totalLeft = fileSize
// Read until the totalLeft.
for totalLeft > 0 {
// Figure out the right blockSize as it was encoded before.
var curBlockSize int
if erasureBlockSize < totalLeft {
curBlockSize = erasureBlockSize
} else {
curBlockSize = int(totalLeft)
}
// Calculate the current encoded block size.
curEncBlockSize := getEncodedBlockLen(curBlockSize, xl.DataBlocks)
enBlocks := make([][]byte, len(xl.storageDisks))
// Loop through all readers and read.
for index, reader := range readers {
// Initialize shard slice and fill the data from each parts.
enBlocks[index] = make([]byte, curEncBlockSize)
if reader == nil {
continue
}
_, err = io.ReadFull(reader, enBlocks[index])
if err != nil && err != io.ErrUnexpectedEOF {
readers[index] = nil
}
}
// TODO need to verify block512Sum.
// Check blocks if they are all zero in length.
if checkBlockSize(enBlocks) == 0 {
err = errors.New("Data likely corrupted, all blocks are zero in length.")
pipeWriter.CloseWithError(err)
return
}
// Verify the blocks.
var ok bool
ok, err = xl.ReedSolomon.Verify(enBlocks)
if err != nil {
pipeWriter.CloseWithError(err)
return
}
// Verification failed, blocks require reconstruction.
if !ok {
for index, reader := range readers {
if reader == nil {
// Reconstruct expects missing blocks to be nil.
enBlocks[index] = nil
}
}
err = xl.ReedSolomon.Reconstruct(enBlocks)
if err != nil {
pipeWriter.CloseWithError(err)
return
}
// Verify reconstructed blocks again.
ok, err = xl.ReedSolomon.Verify(enBlocks)
if err != nil {
pipeWriter.CloseWithError(err)
return
}
if !ok {
// Blocks cannot be reconstructed, corrupted data.
err = errors.New("Verification failed after reconstruction, data likely corrupted.")
pipeWriter.CloseWithError(err)
return
}
}
// Join the decoded blocks.
err = xl.ReedSolomon.Join(pipeWriter, enBlocks, curBlockSize)
if err != nil {
pipeWriter.CloseWithError(err)
return
}
// Save what's left after reading erasureBlockSize.
totalLeft = totalLeft - erasureBlockSize
}
// Cleanly end the pipe after a successful decoding.
pipeWriter.Close()
// Cleanly close all the underlying data readers.
for _, reader := range readers {
if reader == nil {
continue
}
reader.Close()
}
}()
// Return the pipe for the top level caller to start reading.
return pipeReader, nil
}