leveldb/storage/file_storage.go
// Copyright © 2012, Suryandaru Triandana <syndtr@gmail.com>
// Copyright © 2021, Jeffrey H. Johnson <trnsz@pobox.com>
//
// All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package storage
import (
"errors"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"runtime"
"sort"
"strconv"
"strings"
"sync"
"time"
)
var (
errFileOpen = errors.New("leveldb/storage: file still open")
errReadOnly = errors.New("leveldb/storage: storage is read-only")
)
type fileLock interface {
release() error
}
type fileStorageLock struct {
fs *fileStorage
}
func (lock *fileStorageLock) Unlock() {
if lock.fs != nil {
lock.fs.mu.Lock()
defer lock.fs.mu.Unlock()
if lock.fs.slock == lock {
lock.fs.slock = nil
}
}
}
type int64Slice []int64
func (p int64Slice) Len() int { return len(p) }
func (p int64Slice) Less(i, j int) bool { return p[i] < p[j] }
func (p int64Slice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
func writeFileSynced(filename string, data []byte, perm os.FileMode) error {
f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
if err != nil {
return err
}
n, err := f.Write(data)
if err == nil && n < len(data) {
err = io.ErrShortWrite
}
if err1 := f.Sync(); err == nil {
err = err1
}
if err1 := f.Close(); err == nil {
err = err1
}
return err
}
const logSizeThreshold = 1024 * 1024 // 1 MiB
// fileStorage is a file-system backed storage.
type fileStorage struct {
path string
readOnly bool
mu sync.Mutex
flock fileLock
slock *fileStorageLock
logw *os.File
logSize int64
buf []byte
// Opened file counter; if open < 0 means closed.
open int
day int
}
// OpenFile returns a new filesystem-backed storage implementation with the given
// path. This also acquire a file lock, so any subsequent attempt to open the
// same path will fail.
//
// The storage must be closed after use, by calling Close method.
func OpenFile(path string, readOnly bool) (Storage, error) {
if fi, err := os.Stat(path); err == nil {
if !fi.IsDir() {
return nil, fmt.Errorf("leveldb/storage: open %s: not a directory", path)
}
} else if os.IsNotExist(err) && !readOnly {
if err := os.MkdirAll(path, 0o755); err != nil {
return nil, err
}
} else {
return nil, err
}
flock, err := newFileLock(filepath.Join(path, "LOCK"), readOnly)
if err != nil {
return nil, err
}
defer func() {
if err != nil {
flock.release()
}
}()
var (
logw *os.File
logSize int64
)
if !readOnly {
logw, err = os.OpenFile(filepath.Join(path, "LOG"), os.O_WRONLY|os.O_CREATE, 0o644)
if err != nil {
return nil, err
}
logSize, err = logw.Seek(0, os.SEEK_END)
if err != nil {
logw.Close()
return nil, err
}
}
fs := &fileStorage{
path: path,
readOnly: readOnly,
flock: flock,
logw: logw,
logSize: logSize,
}
runtime.SetFinalizer(fs, (*fileStorage).Close)
return fs, nil
}
func (fs *fileStorage) Lock() (Locker, error) {
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return nil, ErrClosed
}
if fs.readOnly {
return &fileStorageLock{}, nil
}
if fs.slock != nil {
return nil, ErrLocked
}
fs.slock = &fileStorageLock{fs: fs}
return fs.slock, nil
}
func itoa(buf []byte, i, wid int) []byte {
u := uint(i)
if u == 0 && wid <= 1 {
return append(buf, '0')
}
// Assemble decimal in reverse order.
var b [32]byte
bp := len(b)
for ; u > 0 || wid > 0; u /= 10 {
bp--
wid--
b[bp] = byte(u%10) + '0'
}
return append(buf, b[bp:]...)
}
func (fs *fileStorage) printDay(t time.Time) {
if fs.day == t.Day() {
return
}
fs.day = t.Day()
fs.logw.Write([]byte("=============== " + t.Format("Jan 2, 2006 (MST)") + " ===============\n"))
}
func (fs *fileStorage) doLog(t time.Time, str string) {
if fs.logSize > logSizeThreshold {
// Rotate log file.
fs.logw.Close()
fs.logw = nil
fs.logSize = 0
rename(filepath.Join(fs.path, "LOG"), filepath.Join(fs.path, "LOG.old"))
}
if fs.logw == nil {
var err error
fs.logw, err = os.OpenFile(filepath.Join(fs.path, "LOG"), os.O_WRONLY|os.O_CREATE, 0o644)
if err != nil {
return
}
// Force printDay on new log file.
fs.day = 0
}
fs.printDay(t)
hour, min, sec := t.Clock()
msec := t.Nanosecond() / 1e3
// time
fs.buf = itoa(fs.buf[:0], hour, 2)
fs.buf = append(fs.buf, ':')
fs.buf = itoa(fs.buf, min, 2)
fs.buf = append(fs.buf, ':')
fs.buf = itoa(fs.buf, sec, 2)
fs.buf = append(fs.buf, '.')
fs.buf = itoa(fs.buf, msec, 6)
fs.buf = append(fs.buf, ' ')
// write
fs.buf = append(fs.buf, []byte(str)...)
fs.buf = append(fs.buf, '\n')
n, _ := fs.logw.Write(fs.buf)
fs.logSize += int64(n)
}
func (fs *fileStorage) Log(str string) {
if !fs.readOnly {
t := time.Now()
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return
}
fs.doLog(t, str)
}
}
func (fs *fileStorage) log(str string) {
if !fs.readOnly {
fs.doLog(time.Now(), str)
}
}
func (fs *fileStorage) setMeta(fd FileDesc) error {
content := fsGenName(fd) + "\n"
// Check and backup old CURRENT file.
currentPath := filepath.Join(fs.path, "CURRENT")
if _, err := os.Stat(currentPath); err == nil {
b, err := ioutil.ReadFile(currentPath)
if err != nil {
fs.log(fmt.Sprintf("backup CURRENT: %v", err))
return err
}
if string(b) == content {
// Content not changed, do nothing.
return nil
}
if err := writeFileSynced(currentPath+".bak", b, 0o644); err != nil {
fs.log(fmt.Sprintf("backup CURRENT: %v", err))
return err
}
} else if !os.IsNotExist(err) {
return err
}
path := fmt.Sprintf("%s.%d", filepath.Join(fs.path, "CURRENT"), fd.Num)
if err := writeFileSynced(path, []byte(content), 0o644); err != nil {
fs.log(fmt.Sprintf("create CURRENT.%d: %v", fd.Num, err))
return err
}
// Replace CURRENT file.
if err := rename(path, currentPath); err != nil {
fs.log(fmt.Sprintf("rename CURRENT.%d: %v", fd.Num, err))
return err
}
// Sync root directory.
if err := syncDir(fs.path); err != nil {
fs.log(fmt.Sprintf("syncDir: %v", err))
return err
}
return nil
}
func (fs *fileStorage) SetMeta(fd FileDesc) error {
if !FileDescOk(fd) {
return ErrInvalidFile
}
if fs.readOnly {
return errReadOnly
}
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return ErrClosed
}
return fs.setMeta(fd)
}
func (fs *fileStorage) GetMeta() (FileDesc, error) {
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return FileDesc{}, ErrClosed
}
dir, err := os.Open(fs.path)
if err != nil {
return FileDesc{}, err
}
names, err := dir.Readdirnames(0)
// Close the dir first before checking for Readdirnames error.
if ce := dir.Close(); ce != nil {
fs.log(fmt.Sprintf("close dir: %v", ce))
}
if err != nil {
return FileDesc{}, err
}
// Try this in order:
// - CURRENT.[0-9]+ ('pending rename' file, descending order)
// - CURRENT
// - CURRENT.bak
//
// Skip corrupted file or file that point to a missing target file.
type currentFile struct {
name string
fd FileDesc
}
tryCurrent := func(name string) (*currentFile, error) {
b, err := ioutil.ReadFile(filepath.Join(fs.path, name))
if err != nil {
if os.IsNotExist(err) {
err = os.ErrNotExist
}
return nil, err
}
var fd FileDesc
if len(b) < 1 || b[len(b)-1] != '\n' || !fsParseNamePtr(string(b[:len(b)-1]), &fd) {
fs.log(fmt.Sprintf("%s: corrupted content: %q", name, b))
err := &ErrCorrupted{
Err: errors.New("leveldb/storage: corrupted or incomplete CURRENT file"),
}
return nil, err
}
if _, err := os.Stat(filepath.Join(fs.path, fsGenName(fd))); err != nil {
if os.IsNotExist(err) {
fs.log(fmt.Sprintf("%s: missing target file: %s", name, fd))
err = os.ErrNotExist
}
return nil, err
}
return ¤tFile{name: name, fd: fd}, nil
}
tryCurrents := func(names []string) (*currentFile, error) {
var (
cur *currentFile
// Last corruption error.
lastCerr error
)
for _, name := range names {
var err error
cur, err = tryCurrent(name)
if err == nil {
break
} else if err == os.ErrNotExist {
// Fallback to the next file.
} else if isCorrupted(err) {
lastCerr = err
// Fallback to the next file.
} else {
// In case the error is due to permission, etc.
return nil, err
}
}
if cur == nil {
err := os.ErrNotExist
if lastCerr != nil {
err = lastCerr
}
return nil, err
}
return cur, nil
}
// Try 'pending rename' files.
var nums []int64
for _, name := range names {
if strings.HasPrefix(name, "CURRENT.") && name != "CURRENT.bak" {
i, err := strconv.ParseInt(name[8:], 10, 64)
if err == nil {
nums = append(nums, i)
}
}
}
var (
pendCur *currentFile
pendErr = os.ErrNotExist
pendNames []string
)
if len(nums) > 0 {
sort.Sort(sort.Reverse(int64Slice(nums)))
pendNames = make([]string, len(nums))
for i, num := range nums {
pendNames[i] = fmt.Sprintf("CURRENT.%d", num)
}
pendCur, pendErr = tryCurrents(pendNames)
if pendErr != nil && pendErr != os.ErrNotExist && !isCorrupted(pendErr) {
return FileDesc{}, pendErr
}
}
// Try CURRENT and CURRENT.bak.
curCur, curErr := tryCurrents([]string{"CURRENT", "CURRENT.bak"})
if curErr != nil && curErr != os.ErrNotExist && !isCorrupted(curErr) {
return FileDesc{}, curErr
}
// pendCur takes precedence, but guards against obsolete pendCur.
if pendCur != nil && (curCur == nil || pendCur.fd.Num > curCur.fd.Num) {
curCur = pendCur
}
if curCur != nil {
// Restore CURRENT file to proper state.
if !fs.readOnly && (curCur.name != "CURRENT" || len(pendNames) != 0) {
// Ignore setMeta errors, however don't delete obsolete files if we
// catch error.
if err := fs.setMeta(curCur.fd); err == nil {
// Remove 'pending rename' files.
for _, name := range pendNames {
if err := os.Remove(filepath.Join(fs.path, name)); err != nil {
fs.log(fmt.Sprintf("remove %s: %v", name, err))
}
}
}
}
return curCur.fd, nil
}
// Nothing found.
if isCorrupted(pendErr) {
return FileDesc{}, pendErr
}
return FileDesc{}, curErr
}
func (fs *fileStorage) List(ft FileType) (fds []FileDesc, err error) {
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return nil, ErrClosed
}
dir, err := os.Open(fs.path)
if err != nil {
return
}
names, err := dir.Readdirnames(0)
// Close the dir first before checking for Readdirnames error.
if cerr := dir.Close(); cerr != nil {
fs.log(fmt.Sprintf("close dir: %v", cerr))
}
if err == nil {
for _, name := range names {
if fd, ok := fsParseName(name); ok && fd.Type&ft != 0 {
fds = append(fds, fd)
}
}
}
return
}
func (fs *fileStorage) Open(fd FileDesc) (Reader, error) {
if !FileDescOk(fd) {
return nil, ErrInvalidFile
}
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return nil, ErrClosed
}
of, err := os.OpenFile(filepath.Join(fs.path, fsGenName(fd)), os.O_RDONLY, 0)
if err != nil {
if fsHasOldName(fd) && os.IsNotExist(err) {
of, err = os.OpenFile(filepath.Join(fs.path, fsGenOldName(fd)), os.O_RDONLY, 0)
if err == nil {
goto ok
}
}
return nil, err
}
ok:
fs.open++
return &fileWrap{File: of, fs: fs, fd: fd}, nil
}
func (fs *fileStorage) Create(fd FileDesc) (Writer, error) {
if !FileDescOk(fd) {
return nil, ErrInvalidFile
}
if fs.readOnly {
return nil, errReadOnly
}
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return nil, ErrClosed
}
of, err := os.OpenFile(filepath.Join(fs.path, fsGenName(fd)), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
if err != nil {
return nil, err
}
fs.open++
return &fileWrap{File: of, fs: fs, fd: fd}, nil
}
func (fs *fileStorage) Remove(fd FileDesc) error {
if !FileDescOk(fd) {
return ErrInvalidFile
}
if fs.readOnly {
return errReadOnly
}
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return ErrClosed
}
err := os.Remove(filepath.Join(fs.path, fsGenName(fd)))
if err != nil {
if fsHasOldName(fd) && os.IsNotExist(err) {
if e1 := os.Remove(filepath.Join(fs.path, fsGenOldName(fd))); !os.IsNotExist(e1) {
fs.log(fmt.Sprintf("remove %s: %v (old name)", fd, err))
err = e1
}
} else {
fs.log(fmt.Sprintf("remove %s: %v", fd, err))
}
}
return err
}
func (fs *fileStorage) Rename(oldfd, newfd FileDesc) error {
if !FileDescOk(oldfd) || !FileDescOk(newfd) {
return ErrInvalidFile
}
if oldfd == newfd {
return nil
}
if fs.readOnly {
return errReadOnly
}
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return ErrClosed
}
return rename(filepath.Join(fs.path, fsGenName(oldfd)), filepath.Join(fs.path, fsGenName(newfd)))
}
func (fs *fileStorage) Close() error {
fs.mu.Lock()
defer fs.mu.Unlock()
if fs.open < 0 {
return ErrClosed
}
// Clear the finalizer.
runtime.SetFinalizer(fs, nil)
if fs.open > 0 {
fs.log(fmt.Sprintf("close: warning, %d files still open", fs.open))
}
fs.open = -1
if fs.logw != nil {
fs.logw.Close()
}
return fs.flock.release()
}
type fileWrap struct {
*os.File
fs *fileStorage
fd FileDesc
closed bool
}
func (fw *fileWrap) Sync() error {
if err := fw.File.Sync(); err != nil {
return err
}
if fw.fd.Type == TypeManifest {
// Also sync parent directory if file type is manifest.
// See: https://code.google.com/p/leveldb/issues/detail?id=190.
if err := syncDir(fw.fs.path); err != nil {
fw.fs.log(fmt.Sprintf("syncDir: %v", err))
return err
}
}
return nil
}
func (fw *fileWrap) Close() error {
fw.fs.mu.Lock()
defer fw.fs.mu.Unlock()
if fw.closed {
return ErrClosed
}
fw.closed = true
fw.fs.open--
err := fw.File.Close()
if err != nil {
fw.fs.log(fmt.Sprintf("close %s: %v", fw.fd, err))
}
return err
}
func fsGenName(fd FileDesc) string {
switch fd.Type {
case TypeManifest:
return fmt.Sprintf("MANIFEST-%06d", fd.Num)
case TypeJournal:
return fmt.Sprintf("%06d.log", fd.Num)
case TypeTable:
return fmt.Sprintf("%06d.ldb", fd.Num)
case TypeTemp:
return fmt.Sprintf("%06d.tmp", fd.Num)
default:
panic("invalid file type")
}
}
func fsHasOldName(fd FileDesc) bool {
return fd.Type == TypeTable
}
func fsGenOldName(fd FileDesc) string {
switch fd.Type {
case TypeTable:
return fmt.Sprintf("%06d.sst", fd.Num)
}
return fsGenName(fd)
}
func fsParseName(name string) (fd FileDesc, ok bool) {
var tail string
_, err := fmt.Sscanf(name, "%d.%s", &fd.Num, &tail)
if err == nil {
switch tail {
case "log":
fd.Type = TypeJournal
case "ldb", "sst":
fd.Type = TypeTable
case "tmp":
fd.Type = TypeTemp
default:
return
}
return fd, true
}
n, _ := fmt.Sscanf(name, "MANIFEST-%d%s", &fd.Num, &tail)
if n == 1 {
fd.Type = TypeManifest
return fd, true
}
return
}
func fsParseNamePtr(name string, fd *FileDesc) bool {
_fd, ok := fsParseName(name)
if fd != nil {
*fd = _fd
}
return ok
}