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XL: Cleanup and add more comments. (#1807)

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Harshavardhana
2016-05-30 16:51:59 -07:00
parent ffc2b3c304
commit 445dc22118
13 changed files with 318 additions and 234 deletions
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66
xl-v1-metadata.go
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@@ -18,7 +18,6 @@ package main
import (
"encoding/json"
"math/rand"
"path"
"sort"
"sync"
@@ -40,6 +39,13 @@ type objectPartInfo struct {
Size int64 `json:"size"`
}
// 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 }
// A xlMetaV1 represents a metadata header mapping keys to sets of values.
type xlMetaV1 struct {
Version string `json:"version"`
@@ -69,12 +75,19 @@ type xlMetaV1 struct {
Parts []objectPartInfo `json:"parts,omitempty"`
}
// 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 }
// 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 = blockSizeV1
xlMeta.Erasure.Distribution = randInts(dataBlocks + parityBlocks)
return xlMeta
}
// ObjectPartIndex - returns the index of matching object part number.
func (m xlMetaV1) ObjectPartIndex(partNumber int) (index int) {
@@ -139,16 +152,13 @@ func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err
// Count for errors encountered.
var xlJSONErrCount = 0
// Allocate 10MiB buffer.
buffer := make([]byte, blockSizeV1)
// Return the first successful lookup from a random list of disks.
for xlJSONErrCount < len(xl.storageDisks) {
disk := xl.getRandomDisk() // Choose a random disk on each attempt.
var n int64
n, err = disk.ReadFile(bucket, path.Join(object, xlMetaJSONFile), int64(0), buffer)
var buffer []byte
buffer, err = readAll(disk, bucket, path.Join(object, xlMetaJSONFile))
if err == nil {
err = json.Unmarshal(buffer[:n], &xlMeta)
err = json.Unmarshal(buffer, &xlMeta)
if err == nil {
return xlMeta, nil
}
@@ -158,20 +168,6 @@ func (xl xlObjects) readXLMetadata(bucket, object string) (xlMeta xlMetaV1, err
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 = blockSizeV1
xlMeta.Erasure.Distribution = randErasureDistribution(dataBlocks + parityBlocks)
return xlMeta
}
// renameXLMetadata - renames `xl.json` from source prefix to destination prefix.
func (xl xlObjects) renameXLMetadata(srcBucket, srcPrefix, dstBucket, dstPrefix string) error {
var wg = &sync.WaitGroup{}
@@ -234,6 +230,7 @@ func (xl xlObjects) writeXLMetadata(bucket, prefix string, xlMeta xlMetaV1) erro
mErrs[index] = err
return
}
// Persist marshalled data.
n, mErr := disk.AppendFile(bucket, jsonFile, metadataBytes)
if mErr != nil {
mErrs[index] = mErr
@@ -259,18 +256,3 @@ func (xl xlObjects) writeXLMetadata(bucket, prefix string, xlMeta xlMetaV1) erro
}
return nil
}
// randErasureDistribution - uses Knuth Fisher-Yates shuffle algorithm.
func randErasureDistribution(numBlocks int) []int {
rand.Seed(time.Now().UTC().UnixNano()) // Seed with current time.
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
}