minio/xl-v1-metadata.go
Harshavardhana b2293c2bf4 XL: Rename, cleanup and add more comments. (#1769)
- xl-v1-bucket.go - removes a whole bunch of code.
- {xl-v1,fs-v1}-metadata.go - add a lot of comments and rename functions
   appropriately.
2016-05-28 15:15:53 -07:00

270 lines
7.5 KiB
Go

/*
* 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 (
"bytes"
"encoding/json"
"io"
"path"
"sort"
"sync"
"time"
)
// Erasure block size.
const (
erasureBlockSize = 4 * 1024 * 1024 // 4MiB.
erasureAlgorithmKlauspost = "klauspost/reedsolomon/vandermonde"
erasureAlgorithmISAL = "isa-l/reedsolomon/cauchy"
)
// objectPartInfo Info of each part kept in the multipart metadata
// file after CompleteMultipartUpload() is called.
type objectPartInfo struct {
Number int `json:"number"`
Name string `json:"name"`
ETag string `json:"etag"`
Size int64 `json:"size"`
}
// A xlMetaV1 represents a metadata header mapping keys to sets of values.
type xlMetaV1 struct {
Version string `json:"version"`
Format string `json:"format"`
Stat struct {
Size int64 `json:"size"`
ModTime time.Time `json:"modTime"`
Version int64 `json:"version"`
} `json:"stat"`
Erasure struct {
Algorithm string `json:"algorithm"`
DataBlocks int `json:"data"`
ParityBlocks int `json:"parity"`
BlockSize int64 `json:"blockSize"`
Index int `json:"index"`
Distribution []int `json:"distribution"`
Checksum []struct {
Name string `json:"name"`
Algorithm string `json:"algorithm"`
Hash string `json:"hash"`
} `json:"checksum"`
} `json:"erasure"`
Minio struct {
Release string `json:"release"`
} `json:"minio"`
Meta map[string]string `json:"meta"`
Parts []objectPartInfo `json:"parts,omitempty"`
}
// ReadFrom - read from implements io.ReaderFrom interface for
// unmarshalling xlMetaV1.
func (m *xlMetaV1) ReadFrom(reader io.Reader) (n int64, err error) {
var buffer bytes.Buffer
n, err = buffer.ReadFrom(reader)
if err != nil {
return 0, err
}
err = json.Unmarshal(buffer.Bytes(), m)
return n, err
}
// WriteTo - write to implements io.WriterTo interface for marshalling xlMetaV1.
func (m xlMetaV1) WriteTo(writer io.Writer) (n int64, err error) {
metadataBytes, err := json.Marshal(&m)
if err != nil {
return 0, err
}
p, err := writer.Write(metadataBytes)
return int64(p), err
}
// byPartName is a collection satisfying sort.Interface.
type byPartNumber []objectPartInfo
func (t byPartNumber) Len() int { return len(t) }
func (t byPartNumber) Swap(i, j int) { t[i], t[j] = t[j], t[i] }
func (t byPartNumber) Less(i, j int) bool { return t[i].Number < t[j].Number }
// ObjectPartIndex - returns the index of matching object part number.
func (m xlMetaV1) ObjectPartIndex(partNumber int) (index int) {
for i, part := range m.Parts {
if partNumber == part.Number {
index = i
return index
}
}
return -1
}
// AddObjectPart - add a new object part in order.
func (m *xlMetaV1) AddObjectPart(partNumber int, partName string, partETag string, partSize int64) {
partInfo := objectPartInfo{
Number: partNumber,
Name: partName,
ETag: partETag,
Size: partSize,
}
// Update part info if it already exists.
for i, part := range m.Parts {
if partNumber == part.Number {
m.Parts[i] = partInfo
return
}
}
// Proceed to include new part info.
m.Parts = append(m.Parts, partInfo)
// Parts in xlMeta should be in sorted order by part number.
sort.Sort(byPartNumber(m.Parts))
}
// objectToPartOffset - translate offset of an object to offset of its individual part.
func (m xlMetaV1) objectToPartOffset(offset int64) (partIndex int, partOffset int64, err error) {
partOffset = offset
// Seek until object offset maps to a particular part offset.
for i, part := range m.Parts {
partIndex = i
// Last part can be of '0' bytes, treat it specially and
// return right here.
if part.Size == 0 {
return partIndex, partOffset, nil
}
// Offset is smaller than size we have reached the proper part offset.
if partOffset < part.Size {
return partIndex, partOffset, nil
}
// Continue to towards the next part.
partOffset -= part.Size
}
// Offset beyond the size of the object return InvalidRange.
return 0, 0, InvalidRange{}
}
// readXLMetadata - returns the object metadata `xl.json` content from
// one of the disks picked at random.
func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err error) {
// Count for errors encountered.
var xlJSONErrCount = 0
// Return the first successful lookup from a random list of disks.
for xlJSONErrCount < len(xl.storageDisks) {
var r io.ReadCloser
disk := xl.getRandomDisk() // Choose a random disk on each attempt.
r, err = disk.ReadFile(bucket, path.Join(object, xlMetaJSONFile), int64(0))
if err == nil {
defer r.Close()
_, err = xlMeta.ReadFrom(r)
if err == nil {
return xlMeta, nil
}
}
xlJSONErrCount++ // Update error count.
}
return xlMetaV1{}, err
}
// newXLMetaV1 - initializes new xlMetaV1.
func newXLMetaV1(dataBlocks, parityBlocks int) (xlMeta xlMetaV1) {
xlMeta = xlMetaV1{}
xlMeta.Version = "1"
xlMeta.Format = "xl"
xlMeta.Minio.Release = minioReleaseTag
xlMeta.Erasure.Algorithm = erasureAlgorithmKlauspost
xlMeta.Erasure.DataBlocks = dataBlocks
xlMeta.Erasure.ParityBlocks = parityBlocks
xlMeta.Erasure.BlockSize = erasureBlockSize
xlMeta.Erasure.Distribution = randErasureDistribution(dataBlocks + parityBlocks)
return xlMeta
}
// writeXLMetadata - write `xl.json` on all disks in order.
func (xl xlObjects) writeXLMetadata(bucket, prefix string, xlMeta xlMetaV1) error {
var wg = &sync.WaitGroup{}
var mErrs = make([]error, len(xl.storageDisks))
// Start writing `xl.json` to all disks in parallel.
for index, disk := range xl.storageDisks {
wg.Add(1)
// Write `xl.json` in a routine.
go func(index int, disk StorageAPI, metadata xlMetaV1) {
defer wg.Done()
metaJSONFile := path.Join(prefix, xlMetaJSONFile)
metaWriter, mErr := disk.CreateFile(bucket, metaJSONFile)
if mErr != nil {
mErrs[index] = mErr
return
}
// Save the disk order index.
metadata.Erasure.Index = index + 1
// Marshal metadata to the writer.
_, mErr = metadata.WriteTo(metaWriter)
if mErr != nil {
if mErr = safeCloseAndRemove(metaWriter); mErr != nil {
mErrs[index] = mErr
return
}
mErrs[index] = mErr
return
}
// Verify if close fails with an error.
if mErr = metaWriter.Close(); mErr != nil {
if mErr = safeCloseAndRemove(metaWriter); mErr != nil {
mErrs[index] = mErr
return
}
mErrs[index] = mErr
return
}
mErrs[index] = nil
}(index, disk, xlMeta)
}
// Wait for all the routines.
wg.Wait()
// Return the first error.
for _, err := range mErrs {
if err == nil {
continue
}
return err
}
return nil
}
// randErasureDistribution - uses Knuth Fisher-Yates shuffle algorithm.
func randErasureDistribution(numBlocks int) []int {
distribution := make([]int, numBlocks)
for i := 0; i < numBlocks; i++ {
distribution[i] = i + 1
}
/*
for i := 0; i < numBlocks; i++ {
// Choose index uniformly in [i, numBlocks-1]
r := i + rand.Intn(numBlocks-i)
distribution[r], distribution[i] = distribution[i], distribution[r]
}
*/
return distribution
}