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lockfile.go
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lockfile.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package lockfile
import (
"os"
paths "path"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
)
// Lockfile represents an acquired lockfile.
type Lockfile struct {
file os.File
}
// Acquire creates the given file path if it doesn't exist and
// obtains an exclusive lock on it. An error is returned if the lock
// has been obtained by another process.
func Acquire(path string) (*Lockfile, error) {
file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0666)
if err != nil {
return nil, errors.Wrap(err, "failed opening lock path")
}
ft := &unix.Flock_t{
Pid: int32(os.Getpid()),
Type: unix.F_WRLCK,
}
if err = unix.FcntlFlock(file.Fd(), unix.F_SETLK, ft); err != nil {
return nil, errors.Wrap(err, "failed obtaining lock")
}
lf := Lockfile{*file}
return &lf, nil
}
// CreateAndAcquire creates any non-existing directories needed to
// create the lock file, then acquires a lock on it
func CreateAndAcquire(path string, newDirMode os.FileMode) (*Lockfile, error) {
if err := os.MkdirAll(paths.Dir(path), newDirMode); err != nil {
return nil, err
}
return Acquire(path)
}
// Release releases the lock on the file and removes the file.
func (lf Lockfile) Release() error {
ft := &unix.Flock_t{
Pid: int32(os.Getpid()),
Type: unix.F_UNLCK,
}
if err := unix.FcntlFlock(lf.file.Fd(), unix.F_SETLK, ft); err != nil {
return errors.Wrap(err, "failed releasing lock")
}
if err := lf.file.Close(); err != nil {
return errors.Wrap(err, "failed closing lock file descriptor")
}
if err := os.Remove(lf.file.Name()); err != nil {
return errors.Wrap(err, "failed removing lock file")
}
return nil
}