Golang fileutil.LockFile函数代码示例

// openLast opens the last wal file for read and write.
func openLast(dirpath string) (*fileutil.LockedFile, error) {
	names, err := readWalNames(dirpath)
	if err != nil {
		return nil, err
	}
	last := path.Join(dirpath, names[len(names)-1])
	return fileutil.LockFile(last, os.O_RDWR, fileutil.PrivateFileMode)
}

// Create creates a WAL ready for appending records. The given metadata is
// recorded at the head of each WAL file, and can be retrieved with ReadAll.
func Create(dirpath string, metadata []byte) (*WAL, error) {
	if Exist(dirpath) {
		return nil, os.ErrExist
	}

	// keep temporary wal directory so WAL initialization appears atomic
	tmpdirpath := path.Clean(dirpath) + ".tmp"
	if fileutil.Exist(tmpdirpath) {
		if err := os.RemoveAll(tmpdirpath); err != nil {
			return nil, err
		}
	}
	if err := os.MkdirAll(tmpdirpath, fileutil.PrivateDirMode); err != nil {
		return nil, err
	}

	p := path.Join(tmpdirpath, walName(0, 0))
	f, err := fileutil.LockFile(p, os.O_WRONLY|os.O_CREATE, fileutil.PrivateFileMode)
	if err != nil {
		return nil, err
	}
	if _, err := f.Seek(0, os.SEEK_END); err != nil {
		return nil, err
	}
	if err := fileutil.Preallocate(f.File, segmentSizeBytes, true); err != nil {
		return nil, err
	}

	w := &WAL{
		dir:      dirpath,
		metadata: metadata,
		encoder:  newEncoder(f, 0),
	}
	w.locks = append(w.locks, f)
	if err := w.saveCrc(0); err != nil {
		return nil, err
	}
	if err := w.encoder.encode(&walpb.Record{Type: metadataType, Data: metadata}); err != nil {
		return nil, err
	}
	if err := w.SaveSnapshot(walpb.Snapshot{}); err != nil {
		return nil, err
	}

	if err := os.RemoveAll(dirpath); err != nil {
		return nil, err
	}
	if err := os.Rename(tmpdirpath, dirpath); err != nil {
		return nil, err
	}

	w.fp = newFilePipeline(w.dir, segmentSizeBytes)
	return w, nil
}

// openLast opens the last wal file for read and write.
func openLast(dirpath string) (*fileutil.LockedFile, error) {
	names, err := fileutil.ReadDir(dirpath)
	if err != nil {
		return nil, err
	}
	names = checkWalNames(names)
	if len(names) == 0 {
		return nil, ErrFileNotFound
	}
	last := path.Join(dirpath, names[len(names)-1])
	return fileutil.LockFile(last, os.O_RDWR, 0600)
}

func (fp *filePipeline) alloc() (f *fileutil.LockedFile, err error) {
	fpath := path.Join(fp.dir, fmt.Sprintf("%d.tmp", fp.count))
	if f, err = fileutil.LockFile(fpath, os.O_CREATE|os.O_WRONLY, 0600); err != nil {
		return nil, err
	}
	if err = fileutil.Preallocate(f.File, fp.size, true); err != nil {
		plog.Errorf("failed to allocate space when creating new wal file (%v)", err)
		f.Close()
		return nil, err
	}
	fp.count++
	return f, nil
}

func (fp *filePipeline) alloc() (f *fileutil.LockedFile, err error) {
	// count % 2 so this file isn't the same as the one last published
	fpath := path.Join(fp.dir, fmt.Sprintf("%d.tmp", fp.count%2))
	if f, err = fileutil.LockFile(fpath, os.O_CREATE|os.O_WRONLY, fileutil.PrivateFileMode); err != nil {
		return nil, err
	}
	if err = fileutil.Preallocate(f.File, fp.size, true); err != nil {
		plog.Errorf("failed to allocate space when creating new wal file (%v)", err)
		f.Close()
		return nil, err
	}
	fp.count++
	return f, nil
}

// Retrieves the path for the cache file. It checks the following directories
// in this specific order:
//  1. $HOME/.cache
//  2. /tmp
// It will try to open (or create if it doesn't exist) the cache file in each
// directory until it finds a directory that is accessible.
func cachePath() *os.File {
	candidates := []string{filepath.Join(os.Getenv("HOME"), ".cache"), "/tmp"}

	for _, dir := range candidates {
		dirs := strings.Split(dir, ":")
		for _, d := range dirs {
			name := filepath.Join(d, cacheName)
			lock, err := fileutil.LockFile(name, os.O_RDWR|os.O_CREATE, 0666)
			if err == nil {
				return lock.File
			}
		}
	}
	return nil
}

// Create creates a WAL ready for appending records. The given metadata is
// recorded at the head of each WAL file, and can be retrieved with ReadAll.
func Create(dirpath string, metadata []byte) (*WAL, error) {
	if Exist(dirpath) {
		return nil, os.ErrExist
	}

	if err := os.MkdirAll(dirpath, privateDirMode); err != nil {
		return nil, err
	}

	p := path.Join(dirpath, walName(0, 0))
	f, err := fileutil.LockFile(p, os.O_WRONLY|os.O_CREATE, 0600)
	if err != nil {
		return nil, err
	}
	if _, err := f.Seek(0, os.SEEK_END); err != nil {
		return nil, err
	}
	if err := fileutil.Preallocate(f.File, segmentSizeBytes, true); err != nil {
		return nil, err
	}

	w := &WAL{
		dir:      dirpath,
		metadata: metadata,
		encoder:  newEncoder(f, 0),
		fp:       newFilePipeline(dirpath, segmentSizeBytes),
	}
	w.locks = append(w.locks, f)
	if err := w.saveCrc(0); err != nil {
		return nil, err
	}
	if err := w.encoder.encode(&walpb.Record{Type: metadataType, Data: metadata}); err != nil {
		return nil, err
	}
	if err := w.SaveSnapshot(walpb.Snapshot{}); err != nil {
		return nil, err
	}
	return w, nil
}

// Writes all the cached data back to the cache file. This is needed because
// functions like `inSUSE` only write to memory. Therefore, once you're done
// with this instance, you should call this function to keep everything synced.
func (cd *cachedData) flush() {
	if !cd.Valid {
		// Silently fail, the user has probably already been notified about it.
		return
	}

	file, err := fileutil.LockFile(cd.Path, os.O_RDWR, 0666)
	if err != nil {
		log.Printf("Cannot write to the cache file: %v", err)
		return
	}
	defer file.Close()

	_, err = file.Stat()
	if err != nil {
		log.Printf("Cannot stat file: %v", err)
		return
	}

	// Read cache from file (again) before writing to it, otherwise the
	// cache will possibly be inconsistent.
	oldCache := cd.readCache(file)

	// Merge the old and "new" cache, and remove duplicates.
	cd.Suse = append(cd.Suse, oldCache.Suse...)
	cd.Other = append(cd.Other, oldCache.Other...)
	cd.Outdated = append(cd.Outdated, oldCache.Outdated...)
	cd.Suse = removeDuplicates(cd.Suse)
	cd.Other = removeDuplicates(cd.Other)
	cd.Outdated = removeDuplicates(cd.Outdated)

	// Clear file content.
	file.Seek(0, 0)
	file.Truncate(0)

	enc := json.NewEncoder(file)
	_ = enc.Encode(cd)
}

// cut closes current file written and creates a new one ready to append.
// cut first creates a temp wal file and writes necessary headers into it.
// Then cut atomically rename temp wal file to a wal file.
func (w *WAL) cut() error {
	// close old wal file; truncate to avoid wasting space if an early cut
	off, serr := w.tail().Seek(0, os.SEEK_CUR)
	if serr != nil {
		return serr
	}
	if err := w.tail().Truncate(off); err != nil {
		return err
	}
	if err := w.sync(); err != nil {
		return err
	}

	fpath := path.Join(w.dir, walName(w.seq()+1, w.enti+1))

	// create a temp wal file with name sequence + 1, or truncate the existing one
	newTail, err := w.fp.Open()
	if err != nil {
		return err
	}

	// update writer and save the previous crc
	w.locks = append(w.locks, newTail)
	prevCrc := w.encoder.crc.Sum32()
	w.encoder = newEncoder(w.tail(), prevCrc)
	if err = w.saveCrc(prevCrc); err != nil {
		return err
	}
	if err = w.encoder.encode(&walpb.Record{Type: metadataType, Data: w.metadata}); err != nil {
		return err
	}
	if err = w.saveState(&w.state); err != nil {
		return err
	}
	// atomically move temp wal file to wal file
	if err = w.sync(); err != nil {
		return err
	}

	off, err = w.tail().Seek(0, os.SEEK_CUR)
	if err != nil {
		return err
	}

	if err = os.Rename(newTail.Name(), fpath); err != nil {
		return err
	}
	newTail.Close()

	if newTail, err = fileutil.LockFile(fpath, os.O_WRONLY, fileutil.PrivateFileMode); err != nil {
		return err
	}
	if _, err = newTail.Seek(off, os.SEEK_SET); err != nil {
		return err
	}

	w.locks[len(w.locks)-1] = newTail

	prevCrc = w.encoder.crc.Sum32()
	w.encoder = newEncoder(w.tail(), prevCrc)

	plog.Infof("segmented wal file %v is created", fpath)
	return nil
}

// Create creates a WAL ready for appending records. The given metadata is
// recorded at the head of each WAL file, and can be retrieved with ReadAll.
func Create(dirpath string, metadata []byte) (*WAL, error) {
	if Exist(dirpath) {
		return nil, os.ErrExist
	}

	// keep temporary wal directory so WAL initialization appears atomic
	tmpdirpath := path.Clean(dirpath) + ".tmp"
	if fileutil.Exist(tmpdirpath) {
		if err := os.RemoveAll(tmpdirpath); err != nil {
			return nil, err
		}
	}
	if err := fileutil.CreateDirAll(tmpdirpath); err != nil {
		return nil, err
	}

	p := path.Join(tmpdirpath, walName(0, 0))
	f, err := fileutil.LockFile(p, os.O_WRONLY|os.O_CREATE, fileutil.PrivateFileMode)
	if err != nil {
		return nil, err
	}
	if _, err = f.Seek(0, os.SEEK_END); err != nil {
		return nil, err
	}
	if err = fileutil.Preallocate(f.File, SegmentSizeBytes, true); err != nil {
		return nil, err
	}

	w := &WAL{
		dir:      dirpath,
		metadata: metadata,
		encoder:  newEncoder(f, 0),
	}
	w.locks = append(w.locks, f)
	if err = w.saveCrc(0); err != nil {
		return nil, err
	}
	if err = w.encoder.encode(&walpb.Record{Type: metadataType, Data: metadata}); err != nil {
		return nil, err
	}
	if err = w.SaveSnapshot(walpb.Snapshot{}); err != nil {
		return nil, err
	}

	if w, err = w.renameWal(tmpdirpath); err != nil {
		return nil, err
	}

	// directory was renamed; sync parent dir to persist rename
	pdir, perr := fileutil.OpenDir(path.Dir(w.dir))
	if perr != nil {
		return nil, perr
	}
	if perr = fileutil.Fsync(pdir); perr != nil {
		return nil, perr
	}
	if perr = pdir.Close(); err != nil {
		return nil, perr
	}

	return w, nil
}

// Create creates a WAL ready for appending records. The given metadata is
// recorded at the head of each WAL file, and can be retrieved with ReadAll.
func Create(dirpath string, metadata []byte) (*WAL, error) {
	if Exist(dirpath) {
		return nil, os.ErrExist
	}

	// keep temporary wal directory so WAL initialization appears atomic
	tmpdirpath := path.Clean(dirpath) + ".tmp"
	if fileutil.Exist(tmpdirpath) {
		if err := os.RemoveAll(tmpdirpath); err != nil {
			return nil, err
		}
	}
	if err := fileutil.CreateDirAll(tmpdirpath); err != nil {
		return nil, err
	}

	p := path.Join(tmpdirpath, walName(0, 0))
	f, err := fileutil.LockFile(p, os.O_WRONLY|os.O_CREATE, fileutil.PrivateFileMode)
	if err != nil {
		return nil, err
	}
	if _, err := f.Seek(0, os.SEEK_END); err != nil {
		return nil, err
	}
	if err := fileutil.Preallocate(f.File, SegmentSizeBytes, true); err != nil {
		return nil, err
	}

	w := &WAL{
		dir:      dirpath,
		metadata: metadata,
		encoder:  newEncoder(f, 0),
	}
	w.locks = append(w.locks, f)
	if err := w.saveCrc(0); err != nil {
		return nil, err
	}
	if err := w.encoder.encode(&walpb.Record{Type: metadataType, Data: metadata}); err != nil {
		return nil, err
	}
	if err := w.SaveSnapshot(walpb.Snapshot{}); err != nil {
		return nil, err
	}

	// rename of directory with locked files doesn't work on windows; close
	// the WAL to release the locks so the directory can be renamed
	w.Close()
	if err := os.Rename(tmpdirpath, dirpath); err != nil {
		return nil, err
	}
	// reopen and relock
	newWAL, oerr := Open(dirpath, walpb.Snapshot{})
	if oerr != nil {
		return nil, oerr
	}
	if _, _, _, err := newWAL.ReadAll(); err != nil {
		newWAL.Close()
		return nil, err
	}
	return newWAL, nil
}