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Copy pathbitrot-streaming.go
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172 lines (159 loc) · 4.92 KB
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/*
* Minio Cloud Storage, (C) 2019 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 cmd
import (
"bytes"
"context"
"encoding/hex"
"hash"
"io"
"github.com/minio/minio/cmd/logger"
)
// Calculates bitrot in chunks and writes the hash into the stream.
type streamingBitrotWriter struct {
iow *io.PipeWriter
h hash.Hash
shardSize int64
canClose chan struct{} // Needed to avoid race explained in Close() call.
// Following two fields are used only to make sure that Write(p) is called such that
// len(p) is always the block size except the last block, i.e prevent programmer errors.
currentBlockIdx int
verifyTillIdx int
}
func (b *streamingBitrotWriter) Write(p []byte) (int, error) {
if b.currentBlockIdx < b.verifyTillIdx && int64(len(p)) != b.shardSize {
// All blocks except last should be of the length b.shardSize
logger.LogIf(context.Background(), errUnexpected)
return 0, errUnexpected
}
if len(p) == 0 {
return 0, nil
}
b.h.Reset()
b.h.Write(p)
hashBytes := b.h.Sum(nil)
n, err := b.iow.Write(hashBytes)
if n != len(hashBytes) {
logger.LogIf(context.Background(), err)
return 0, err
}
n, err = b.iow.Write(p)
b.currentBlockIdx++
return n, err
}
func (b *streamingBitrotWriter) Close() error {
err := b.iow.Close()
// Wait for all data to be written before returning else it causes race conditions.
// Race condition is because of io.PipeWriter implementation. i.e consider the following
// sequent of operations:
// 1) pipe.Write()
// 2) pipe.Close()
// Now pipe.Close() can return before the data is read on the other end of the pipe and written to the disk
// Hence an immediate Read() on the file can return incorrect data.
<-b.canClose
return err
}
// Returns streaming bitrot writer implementation.
func newStreamingBitrotWriter(disk StorageAPI, volume, filePath string, length int64, algo BitrotAlgorithm, shardSize int64) io.WriteCloser {
r, w := io.Pipe()
h := algo.New()
bw := &streamingBitrotWriter{w, h, shardSize, make(chan struct{}), 0, int(length / shardSize)}
go func() {
bitrotSumsTotalSize := ceilFrac(length, shardSize) * int64(h.Size()) // Size used for storing bitrot checksums.
totalFileSize := bitrotSumsTotalSize + length
err := disk.CreateFile(volume, filePath, totalFileSize, r)
if err != nil {
logger.LogIf(context.Background(), err)
r.CloseWithError(err)
}
close(bw.canClose)
}()
return bw
}
// ReadAt() implementation which verifies the bitrot hash available as part of the stream.
type streamingBitrotReader struct {
disk StorageAPI
rc io.ReadCloser
volume string
filePath string
tillOffset int64
currOffset int64
h hash.Hash
shardSize int64
hashBytes []byte
}
func (b *streamingBitrotReader) Close() error {
if b.rc == nil {
return nil
}
return b.rc.Close()
}
func (b *streamingBitrotReader) ReadAt(buf []byte, offset int64) (int, error) {
var err error
if offset%b.shardSize != 0 {
// Offset should always be aligned to b.shardSize
logger.LogIf(context.Background(), errUnexpected)
return 0, errUnexpected
}
if b.rc == nil {
// For the first ReadAt() call we need to open the stream for reading.
b.currOffset = offset
streamOffset := (offset/b.shardSize)*int64(b.h.Size()) + offset
b.rc, err = b.disk.ReadFileStream(b.volume, b.filePath, streamOffset, b.tillOffset-streamOffset)
if err != nil {
logger.LogIf(context.Background(), err)
return 0, err
}
}
if offset != b.currOffset {
logger.LogIf(context.Background(), errUnexpected)
return 0, errUnexpected
}
b.h.Reset()
_, err = io.ReadFull(b.rc, b.hashBytes)
if err != nil {
logger.LogIf(context.Background(), err)
return 0, err
}
_, err = io.ReadFull(b.rc, buf)
if err != nil {
logger.LogIf(context.Background(), err)
return 0, err
}
b.h.Write(buf)
if !bytes.Equal(b.h.Sum(nil), b.hashBytes) {
err = hashMismatchError{hex.EncodeToString(b.hashBytes), hex.EncodeToString(b.h.Sum(nil))}
logger.LogIf(context.Background(), err)
return 0, err
}
b.currOffset += int64(len(buf))
return len(buf), nil
}
// Returns streaming bitrot reader implementation.
func newStreamingBitrotReader(disk StorageAPI, volume, filePath string, tillOffset int64, algo BitrotAlgorithm, shardSize int64) *streamingBitrotReader {
h := algo.New()
return &streamingBitrotReader{
disk,
nil,
volume,
filePath,
ceilFrac(tillOffset, shardSize)*int64(h.Size()) + tillOffset,
0,
h,
shardSize,
make([]byte, h.Size()),
}
}