/
metadata.go
409 lines (328 loc) · 7.26 KB
/
metadata.go
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package siva
import (
"io/ioutil"
"os"
"time"
billy "gopkg.in/src-d/go-billy.v4"
errors "gopkg.in/src-d/go-errors.v1"
"github.com/ghodss/yaml"
"github.com/google/uuid"
"gopkg.in/src-d/go-billy.v4/util"
)
const (
libraryMetadataFile = "library.yaml"
)
type libMetadata struct {
// ID is the library indentifyer. It is a generated UUID id no ID is
// provided.
ID string `json:"id,omitempty"`
// CurrentVersion holds the version used for reading.
CurrentVersion int `json:"version"`
dirty bool
fs billy.Filesystem
size int64
modTime time.Time
}
// loadOrCreateLibraryMetadata loads the library metadata from disk. If the data
// doesn't exist on disk it creates new data generating a new ID in case the
// passed id is an empty string..
func loadOrCreateLibraryMetadata(
id string,
fs billy.Filesystem,
) (*libMetadata, error) {
m, err := loadLibraryMetadata(fs)
if err == nil || !os.IsNotExist(err) {
return m, err
}
if id == "" {
var err error
id, err = generateLibID()
if err != nil {
return nil, err
}
}
return newLibraryMetadata(id, fs)
}
// newLibraryMetadata builds a new libMetadata. It persists the data on disk.
func newLibraryMetadata(
id string,
fs billy.Filesystem,
) (*libMetadata, error) {
m := &libMetadata{
ID: id,
CurrentVersion: -1,
fs: fs,
dirty: true,
}
if err := m.save(); err != nil {
return nil, err
}
fi, err := fs.Stat(libraryMetadataFile)
if err != nil {
return nil, err
}
m.fs = fs
m.modTime = fi.ModTime()
m.size = fi.Size()
return m, nil
}
// version returns the version stored in the library metadata file or -1
// if it's not set.
func (m *libMetadata) version() (int, error) {
if m.dirty {
return m.CurrentVersion, nil
}
fi, err := m.fs.Stat(libraryMetadataFile)
if err != nil {
return -1, err
}
if fi.ModTime() != m.modTime || fi.Size() != m.size {
metadata, err := loadLibraryMetadata(m.fs)
if err != nil {
return -1, err
}
m.ID = metadata.ID
m.CurrentVersion = metadata.CurrentVersion
m.modTime = fi.ModTime()
m.size = fi.Size()
m.dirty = false
}
return m.CurrentVersion, nil
}
func (m *libMetadata) setVersion(v int) {
if v != m.CurrentVersion {
m.dirty = true
m.CurrentVersion = v
}
}
// setID changes the current version.
func (m *libMetadata) setID(id string) {
if id != m.ID {
m.dirty = true
m.ID = id
}
}
func generateLibID() (string, error) {
uuid, err := uuid.NewUUID()
if err != nil {
return "", err
}
return uuid.String(), nil
}
func (m *libMetadata) save() error {
if !m.dirty {
return nil
}
data, err := yaml.Marshal(m)
if err != nil {
return err
}
tmp := libraryMetadataFile + ".tmp"
defer m.fs.Remove(tmp)
if err = util.WriteFile(m.fs, tmp, data, 0666); err != nil {
return err
}
if err = m.fs.Rename(tmp, libraryMetadataFile); err != nil {
return err
}
m.dirty = false
return nil
}
func loadLibraryMetadata(fs billy.Filesystem) (*libMetadata, error) {
mf, err := fs.Open(libraryMetadataFile)
if err != nil {
return nil, err
}
defer mf.Close()
data, err := ioutil.ReadAll(mf)
if err != nil {
return nil, err
}
m, err := parseLibraryMetadata(data)
if err != nil {
return nil, err
}
m.fs = fs
fi, err := fs.Stat(libraryMetadataFile)
if err != nil {
return nil, err
}
m.modTime = fi.ModTime()
m.size = fi.Size()
return m, nil
}
func parseLibraryMetadata(d []byte) (*libMetadata, error) {
var metadata libMetadata
err := yaml.Unmarshal(d, &metadata)
if err != nil {
return nil, err
}
return &metadata, nil
}
// Version represents a valid siva file point to read from.
type Version struct {
Offset uint64 `json:"offset"`
Size uint64 `json:"size,omiempty"`
}
type locationMetadata struct {
Versions map[int]*Version `json:"versions"`
dirty bool
fs billy.Filesystem
path string
size int64
modTime time.Time
}
const locMetadataFileExt = ".yaml"
func newLocationMetadata(
fs billy.Filesystem,
path string,
) *locationMetadata {
return &locationMetadata{
Versions: make(map[int]*Version),
fs: fs,
path: path,
}
}
func parseLocationMetadata(d []byte) (*locationMetadata, error) {
var m locationMetadata
err := yaml.Unmarshal(d, &m)
if err != nil {
return nil, err
}
return &m, nil
}
func loadOrCreateLocationMetadata(
fs billy.Filesystem,
path string,
) (*locationMetadata, error) {
m, err := loadLocationMetadata(fs, path)
if os.IsNotExist(err) {
return newLocationMetadata(fs, path), nil
}
return m, err
}
func loadLocationMetadata(
fs billy.Filesystem,
path string,
) (*locationMetadata, error) {
mf, err := fs.Open(path)
if err != nil {
return nil, err
}
defer mf.Close()
data, err := ioutil.ReadAll(mf)
if err != nil {
return nil, err
}
m, err := parseLocationMetadata(data)
if err != nil {
return nil, err
}
m.fs = fs
m.path = path
return m, nil
}
// last returns the last Version or -1 if there are no Versions.
func (m *locationMetadata) last() int {
last := -1
for i := range m.Versions {
if i > last {
last = i
}
}
return last
}
// closest searches for the last Version lesser or equal to the one provided.
func (m *locationMetadata) closest(v int) int {
closest := -1
for i := range m.Versions {
if i <= v && i > closest {
closest = i
}
}
return closest
}
// offset picks the closest Version from metadata and returns its offsets.
// If there are not Versions defined returns offset 0 that means to use
// the latest siva index when used with siva filesystem.
func (m *locationMetadata) offset(c int) (uint64, error) {
version := m.last()
if version < 0 {
return 0, nil
}
b, err := m.version(c)
if err == nil {
return b.Offset, nil
}
if !errLocVersionNotExists.Is(err) {
return 0, err
}
if closest := m.closest(c); closest >= 0 {
version = closest
}
return m.Versions[version].Offset, nil
}
var errLocVersionNotExists = errors.NewKind("location version not exists")
// version returns information for a given version. If the version does not
// exist an error is returned
func (m *locationMetadata) version(v int) (*Version, error) {
if m.dirty {
Version, ok := m.Versions[v]
if !ok {
return nil, errLocVersionNotExists.New()
}
return Version, nil
}
fi, err := m.fs.Stat(m.path)
if err != nil {
return nil, err
}
if fi.ModTime() != m.modTime || fi.Size() != m.size {
metadata, err := loadLocationMetadata(m.fs, m.path)
if err != nil {
return nil, err
}
m.Versions = metadata.Versions
m.modTime = fi.ModTime()
m.size = fi.Size()
m.dirty = false
}
Version, ok := m.Versions[v]
if !ok {
return nil, errLocVersionNotExists.New()
}
return Version, nil
}
func (m *locationMetadata) setVersion(n int, b *Version) {
current, ok := m.Versions[n]
if ok && (current.Offset == b.Offset && current.Size == b.Size) {
return
}
m.Versions[n] = b
m.dirty = true
}
// deleteVersion deletes a given version.
func (m *locationMetadata) deleteVersion(n int) {
_, ok := m.Versions[n]
if !ok {
return
}
delete(m.Versions, n)
m.dirty = true
}
func (m *locationMetadata) save() error {
if !m.dirty {
return nil
}
data, err := yaml.Marshal(m)
if err != nil {
return err
}
tmp := m.path + ".tmp"
defer m.fs.Remove(tmp)
err = util.WriteFile(m.fs, tmp, data, 0666)
if err != nil {
return err
}
return m.fs.Rename(tmp, m.path)
}