agola/internal/objectstorage/atomic.go

88 lines
2.1 KiB
Go

// Copyright 2019 Sorint.lab
//
// 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 objectstorage
import (
"io"
"os"
"path/filepath"
"strings"
"github.com/sorintlab/errors"
)
// writeFileAtomicFunc atomically writes a file, it achieves this by creating a
// temporary file and then moving it. writeFunc is the func that will write
// data to the file.
// TODO(sgotti) remove left over tmp files if process crashes before calling
// os.Remove
func writeFileAtomicFunc(p, baseDir, tmpDir string, perm os.FileMode, persist bool, writeFunc func(f io.Writer) error) error {
f, err := os.CreateTemp(tmpDir, "tmpfile")
if err != nil {
return errors.WithStack(err)
}
err = writeFunc(f)
if persist && err == nil {
err = f.Sync()
}
if closeErr := f.Close(); err == nil {
err = closeErr
}
if permErr := os.Chmod(f.Name(), perm); err == nil {
err = permErr
}
if err == nil {
err = os.Rename(f.Name(), p)
}
if err != nil {
os.Remove(f.Name())
return errors.WithStack(err)
}
if !persist {
return nil
}
// sync parent dirs
pdir := filepath.Dir(p)
for {
if !strings.HasPrefix(pdir, baseDir) {
break
}
f, err := os.Open(pdir)
if err != nil {
f.Close()
return nil
}
if err := f.Sync(); err != nil {
f.Close()
return nil
}
f.Close()
pdir = filepath.Dir(pdir)
}
return nil
}
/*
func writeFileAtomic(filename, baseDir, tmpDir string, perm os.FileMode, persist bool, data []byte) error {
return writeFileAtomicFunc(filename, baseDir, tmpDir, perm, persist,
func(f io.Writer) error {
_, err := f.Write(data)
return errors.WithStack(err)
})
}
*/