func main() {
fd, fd_err := syscall.Open(LOCK_PATH, syscall.O_CREAT, 0)
if fd_err != nil {
fmt.Printf("FD ERR:%v\n", fd_err)
os.Exit(1)
}
flock_err := syscall.Flock(fd, syscall.LOCK_EX)
if flock_err != nil {
fmt.Printf("LOCK ERR:%v\n", flock_err)
os.Exit(1)
}
// beginning of the code getting the exclusive lock
fmt.Printf(".")
time.Sleep(time.Second * 10)
// end of the code getting the exclusive lock
funlock_err := syscall.Flock(fd, syscall.LOCK_UN)
if funlock_err != nil {
fmt.Printf("UNLOCK ERR:%v\n", funlock_err)
unlink_err := syscall.Unlink(LOCK_PATH)
if unlink_err != nil {
fmt.Printf("UNLINK ERR:%v\n", unlink_err)
}
os.Exit(1)
}
close_err := syscall.Close(fd)
if close_err != nil {
fmt.Printf("CLOSE ERR:%v\n", close_err)
}
unlink_err := syscall.Unlink(LOCK_PATH)
if unlink_err != nil {
fmt.Printf("UNLINK ERR:%v\n", unlink_err)
}
}
func setFileLock(f *os.File, lock bool) error {
how := syscall.LOCK_UN
if lock {
how = syscall.LOCK_EX
}
return syscall.Flock(int(f.Fd()), how|syscall.LOCK_NB)
}
/* Append a line to a file f, locking it first. Will return if f is empty */
func appendLine(fname, line string) {
if 0 == len(fname) {
return
}
/* Try to open the successes file */
f, err := os.OpenFile(fname, os.O_WRONLY|os.O_APPEND|os.O_CREATE,
0644)
/* Close on return */
defer f.Close()
/* Give up if we can't */
if err != nil {
log.Printf("Unable to open file %v: %v", f, err)
return
}
/* Acquire an exclusive lock */
if syscall.Flock(int(f.Fd()), syscall.LOCK_EX) != nil {
log.Printf("Unable to lock %v: %v", f, err)
return
}
/* Release it when we're done */
defer syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
/* Write line to file */
r, err := f.WriteString(line)
if err != nil {
log.Printf("Error writing %\"%v\" to %v: %v", line, f,
err)
}
if r < len(line) {
log.Printf("Only wrote %v/%v bytes of \"%v\" to %v", r,
len(line),
line, f)
}
}
func (auth *Authinfo) Store() (err error) {
authFile, err := os.Open(auth.path)
auth.daemonLog.LogError(fmt.Sprintf("Unable to open %s for reading.", auth.path), err)
err = syscall.Flock(int(authFile.Fd()), 2) //2 is exclusive lock
if err != nil {
err = errors.New(fmt.Sprintf("Failed to lock %s for reading.", auth.path))
}
auth.lock.RLock()
defer auth.lock.RUnlock()
data, err := json.Marshal(auth.Users)
_, err = authFile.Write(data)
auth.daemonLog.LogError("Unable to write to file .", err)
err = syscall.Flock(int(authFile.Fd()), 8) //8 is unlock
if err != nil {
err = errors.New(fmt.Sprintf("Unable to unlock %s for reading.", auth.path))
}
fi, err := authFile.Stat()
auth.dbstamp = fi.ModTime().Unix()
authFile.Close()
return
}
// AcquireRepoLock opens the lock file and acquires the lock.
// Dies if the lock cannot be successfully acquired.
func AcquireRepoLock() {
var err error
// There is of course technically a bit of a race condition between the file & flock operations here,
// but it shouldn't matter much since we're trying to mutually exclude plz processes started by the user
// which (one hopes) they wouldn't normally do simultaneously.
os.MkdirAll(path.Dir(lockFilePath), DirPermissions)
// TODO(pebers): This doesn't seem quite as intended, I think the file still gets truncated sometimes.
// Not sure why since I'm not passing O_TRUNC...
if lockFile, err = os.OpenFile(lockFilePath, os.O_RDWR|os.O_CREATE, 0644); err != nil && !os.IsNotExist(err) {
log.Fatalf("Failed to acquire lock: %s", err)
} else if lockFile, err = os.Create(lockFilePath); err != nil {
log.Fatalf("Failed to create lock: %s", err)
}
// Try a non-blocking acquire first so we can warn the user if we're waiting.
log.Debug("Attempting to acquire lock %s...", lockFilePath)
if err := syscall.Flock(int(lockFile.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err == nil {
log.Debug("Acquired lock %s", lockFilePath)
} else {
log.Warning("Looks like another plz is already running in this repo. Waiting for it to finish...")
if err := syscall.Flock(int(lockFile.Fd()), syscall.LOCK_EX); err != nil {
log.Fatalf("Failed to acquire lock: %s", err)
}
}
// Record the operation performed.
if _, err = lockFile.Seek(0, os.SEEK_SET); err == nil {
if n, err := lockFile.Write([]byte(strings.Join(os.Args[1:], " ") + "\n")); err == nil {
lockFile.Truncate(int64(n))
}
}
}
// Checks status of daemonized process.
// Can be used in daemon actions to perate with daemonized process.
func Status() (isRunning bool, pr *os.Process, e error) {
const errLoc = "daemonigo.Status()"
var (
err error
file *os.File
)
file, err = os.Open(PidFile)
if err != nil {
if !os.IsNotExist(err) {
e = fmt.Errorf(
"%s: could not open PID file, reason -> %s",
errLoc, err.Error(),
)
}
return
}
defer file.Close()
fd := int(file.Fd())
if err = syscall.Flock(
fd, syscall.LOCK_EX|syscall.LOCK_NB,
); err != syscall.EWOULDBLOCK {
if err == nil {
syscall.Flock(fd, syscall.LOCK_UN)
} else {
e = fmt.Errorf(
"%s: PID file locking attempt failed, reason -> %s",
errLoc, err.Error(),
)
}
return
}
isRunning = true
var n, pid int
content := make([]byte, 128)
n, err = file.Read(content)
if err != nil && err != io.EOF {
e = fmt.Errorf(
"%s: could not read from PID file, reason -> %s",
errLoc, err.Error(),
)
return
}
pid, err = strconv.Atoi(string(content[:n]))
if n < 1 || err != nil {
e = fmt.Errorf(
"%s: bad PID format, PID file is possibly corrupted", errLoc,
)
return
}
pr, err = os.FindProcess(pid)
if err != nil {
e = fmt.Errorf(
"%s: cannot find process by PID, reason -> %s", errLoc, err.Error(),
)
}
return
}
func (config *ConfigInfo) load() (err error) {
configFile, err := os.Open(config.path)
config.daemonLog.LogError(fmt.Sprintf("Cannot open %s for reading", config.path), err)
if err != nil {
os.Exit(1)
}
err = syscall.Flock(int(configFile.Fd()), 2)
config.daemonLog.LogError("Error: Cannot read file for configurations", err)
configContents, err := ioutil.ReadAll(configFile)
config.daemonLog.LogError(fmt.Sprintf("Cannot read data from %s", config.path), err)
err = syscall.Flock(int(configFile.Fd()), 8)
if err != nil {
config.daemonLog.LogError("Cannot unlock the config file for reading.", errors.New("Flock sys call Failed"))
}
fi, err := configFile.Stat()
config.daemonLog.LogError(fmt.Sprintf("Stat of %s failed", err), err)
err = configFile.Close()
config.daemonLog.LogError("Cannot close file", err)
config.lock.Lock()
defer config.lock.Unlock()
err = json.Unmarshal(configContents, &config.Data)
config.daemonLog.LogError("Cannot unmarshall config.Data", err)
config.tmstamp = fi.ModTime().Unix()
return
}
func readPid(fileName string) (int, error) {
fd, err := os.OpenFile(fileName, os.O_RDWR|os.O_CREATE, 0644)
if err != nil {
return 0, err
}
defer fd.Close()
if err := syscall.Flock(int(fd.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
return 0, fmt.Errorf("can't lock '%s', lock is held", fd.Name())
}
if _, err := fd.Seek(0, 0); err != nil {
return 0, err
}
data, err := ioutil.ReadAll(fd)
if err != nil {
return 0, err
}
pid, err := strconv.Atoi(string(bytes.TrimSpace(data)))
if err != nil {
return 0, fmt.Errorf("error parsing pid from %s: %s", fd.Name(), err)
}
if err := syscall.Flock(int(fd.Fd()), syscall.LOCK_UN); err != nil {
return 0, fmt.Errorf("can't release lock '%s', lock is held", fd.Name())
}
return pid, nil
}
func (r *Samjung) writeDataToFile(rowData []byte) (uint64, error) {
// open file
f, err := os.OpenFile(r.baseDir+"/"+tableFile, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0664)
if err != nil {
return 0, err
}
defer f.Close()
// file lock
err = syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
if err != nil {
return 0, err
}
defer syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
// seek end offset of file
offset, err := f.Seek(0, os.SEEK_END)
if err != nil {
return 0, err
}
// write to file
_, err = f.WriteAt(rowData, offset)
if err != nil {
return 0, err
}
return uint64(offset), nil
}
func setFileLock(fp *os.File, lock bool) error {
if lock {
return syscall.Flock(int(fp.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
} else {
return syscall.Flock(int(fp.Fd()), syscall.LOCK_UN|syscall.LOCK_NB)
}
}
func storeVols() error {
log.Info("Storing volume list...")
VolData.lock.RLock()
js, err := json.MarshalIndent(VolData, "", " ")
VolData.lock.RUnlock()
volFile, err := os.OpenFile(VolData.volFileName, syscall.O_WRONLY|syscall.O_CREAT, 0600)
if err != nil {
log.Error("DV: Cannot open for writing, file: " + DV_VOL_LIST_FILE)
return err
}
defer volFile.Close()
for err := syscall.Flock(int(volFile.Fd()), syscall.LOCK_EX); err == syscall.EINTR; {
}
defer syscall.Flock(int(volFile.Fd()), syscall.LOCK_UN)
volFile.Truncate(0)
_, err = volFile.Write(js)
if err != nil {
log.Errorf("Cannot write vol file - %v", err)
return err
}
return nil
}
func (v *Add) Run(c cli.Command) {
jobName := c.Param("jobname").String()
var job job.Job
if _, err := toml.DecodeFile(metl.GetJobFilePath(jobName)+".toml", &job); err != nil {
log.Fatal(err)
}
cronfile := filepath.Join(metl.Etl.GetLocalStoragePath(), crontabFile)
file, err := os.Open(cronfile)
if err != nil {
file, err = os.Create(cronfile)
if err != nil {
log.WithFields(
log.Fields{
"filename": cronfile,
},
).Fatal("Unable to create cronfile: ", err)
}
}
defer file.Close()
err = syscall.Flock(int(file.Fd()), syscall.LOCK_EX)
if err != nil {
log.Fatal("Failed to lock file")
}
defer func() {
err = syscall.Flock(int(file.Fd()), syscall.LOCK_UN)
if err != nil {
log.Fatal("Failed to unlock file")
}
}()
buffer := make([]string, 0)
if err = jobIsInFile(file, jobName, &buffer); err != nil {
log.Fatal(err)
}
buffer = append(buffer, fmt.Sprintf("%s %s >> %s%s.log", cmd, jobName, logDir, jobName))
tmpf, err := ioutil.TempFile(metl.Etl.GetLocalStoragePath(), "tmp")
if err != nil {
log.Fatal("Unable to create temporary file.")
}
for _, line := range buffer {
if _, err := tmpf.WriteString(line + "\n"); err != nil {
log.Fatal("Unable to write to temporary file")
}
}
if err := os.Rename(tmpf.Name(), cronfile); err != nil {
log.Fatal("Failed to rename temporary lock file:", err)
}
// execute /usr/bin/env crontab cronfile
}
// writeKeys serializes the given key in the authorized_keys file (of the
// current user).
func writeKey(k *Key) error {
file, err := fs.Filesystem().OpenFile(authKey(), os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0644)
if err != nil {
return err
}
defer file.Close()
syscall.Flock(int(file.Fd()), syscall.LOCK_EX)
defer syscall.Flock(int(file.Fd()), syscall.LOCK_UN)
return k.dump(file)
}
func cat_new_mids() (floor uint64, ceiling uint64, tsh uint64, err error) {
tsh = uint64(time.Now().Unix() / 3600)
file, err := OpenFile(TEMPFILE, O_CREATE|O_RDWR, 0664)
if err != nil {
return 0, 0, tsh, errors.New("Unable to open temp file")
}
defer func() {
file.Sync()
file.Close()
syscall.Flock(int(file.Fd()), syscall.LOCK_UN)
}()
share := make([]byte, 16)
syscall.Flock(int(file.Fd()), syscall.LOCK_EX)
n, err := file.Read(share)
if err != nil && err != io.EOF {
return 0, 0, tsh, errors.New("Unable to read temp file")
}
if n == 16 {
var f uint64 = binary.BigEndian.Uint64(share[:8])
var l uint64 = binary.BigEndian.Uint64(share[8:])
if tsh > l {
floor = 1
ceiling = 100000
buf := make([]byte, 8)
binary.BigEndian.PutUint64(buf, uint64(ceiling))
file.WriteAt(buf, 0)
binary.BigEndian.PutUint64(buf, uint64(tsh))
file.WriteAt(buf, 8)
} else {
floor = f
ceiling = f + 100000
buf := make([]byte, 8)
binary.BigEndian.PutUint64(buf, uint64(ceiling))
file.WriteAt(buf, 0)
}
} else if n == 0 {
floor = 1
ceiling = 100000
buf := make([]byte, 8)
binary.BigEndian.PutUint64(buf, uint64(ceiling))
n, err = file.WriteAt(buf, 0)
if err != nil {
return 0, 0, tsh, errors.New("Unable to write index to temp file")
}
binary.BigEndian.PutUint64(buf, uint64(tsh))
n, err = file.WriteAt(buf, 8)
if err != nil {
return 0, 0, tsh, errors.New("Unable to write tsh to temp file")
}
} else {
return 0, 0, tsh, errors.New("Temp file is herpahs corrupted")
}
return floor, ceiling, tsh, nil
}
func (r *Samjung) getAutoIncrement() (uint64, error) {
isExist := true
if _, err := os.Stat(r.baseDir + "/" + autoIncFile); os.IsNotExist(err) {
isExist = false
}
// autoIncFile 없으면 파일 생성하면서 1 집어넣음
if isExist == false {
f, err := os.OpenFile(r.baseDir+"/"+autoIncFile, os.O_WRONLY|os.O_CREATE, 0664)
if err != nil {
return 0, err
}
defer f.Close()
_, err = f.WriteString("1")
if err != nil {
return 0, err
}
return 1, nil
}
// 있으면 + 1 해서 리턴해주고 저장
f, err := os.OpenFile(r.baseDir+"/"+autoIncFile, os.O_WRONLY, 0664)
if err != nil {
return 0, err
}
defer f.Close()
// file lock
err = syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
if err != nil {
return 0, err
}
defer syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
numByte, err := ioutil.ReadFile(r.baseDir + "/" + autoIncFile)
if err != nil {
return 0, err
}
number, err := strconv.ParseUint(string(numByte), 10, 64)
if err != nil {
return 0, err
}
number = number + 1
_, err = f.WriteString(strconv.FormatUint(number, 10))
if err != nil {
return 0, err
}
return number, nil
}
// Write writes a json marshalled, base64 encoded string
// to file. `data` must be json serializable.
func (f *Failover) Write(data interface{}) {
msg, err := json.Marshal(data)
if err != nil {
log.Println(err)
return
}
encodedData := string(base64.StdEncoding.EncodeToString(msg))
fd := int(f.File.Fd())
syscall.Flock(fd, syscall.LOCK_SH)
f.File.WriteString(fmt.Sprintf("%s\n", encodedData))
syscall.Flock(fd, syscall.LOCK_UN)
}
// Saves Meta data from dirTree to meta File
func saveMeta(data *ReveloData) error {
var Meta *horcrux.Meta
var err error
data.lock.RLock()
Meta, err = dirTree.GetMeta(data.Root)
Meta.Config = data.Config
Meta.CurrVer = data.CurrVer
data.lock.RUnlock()
if err != nil {
log.Error("saveMeta: Cannot get Meta data")
return err
}
js, err := json.MarshalIndent(Meta, "", " ")
if err != nil {
log.WithFields(
log.Fields{"Meta": Meta, "Error": err}).Error("saveMeta: Cannot marshal meta")
return err
}
metaFile, err := os.OpenFile(data.cacheDir+"/"+data.metaName, os.O_WRONLY|os.O_SYNC, 0600)
if err != nil {
log.WithFields(log.Fields{"Meta File": data.metaName, "Error": err}).Error("saveMeta: Cannot open meta file")
return err
}
defer metaFile.Close()
// XXX Using File EX lock to avoid multiple access
for err = syscall.Flock(int(metaFile.Fd()), syscall.LOCK_EX); err == syscall.EINTR; {
}
if err != nil {
log.WithFields(log.Fields{"Error": err}).Error("saveMeta: Cannot lock meta file")
return err
}
defer syscall.Flock(int(metaFile.Fd()), syscall.LOCK_UN)
metaFile.Truncate(0) //XXX: Do Truncate(n) after write succeeds!!
n, err := metaFile.Write(js)
if err != nil {
log.WithFields(log.Fields{
"Meta file": data.metaName, "Wrote": n, "Size": len(js), "Error": err,
}).Error("saveMeta: Cannot write to meta file")
return err
}
log.Debug("saveMeta: Done")
return nil
}
func deleteReservation(checkUser bool, args []string) {
if len(args) != 1 {
fatalf("Invalid arguments")
}
user, err := user.Current()
path := filepath.Join(igorConfig.TFTPRoot, "/igor/reservations.json")
resdb, err := os.OpenFile(path, os.O_RDWR, 664)
if err != nil {
fatalf("failed to open reservations file: %v", err)
}
defer resdb.Close()
err = syscall.Flock(int(resdb.Fd()), syscall.LOCK_EX)
defer syscall.Flock(int(resdb.Fd()), syscall.LOCK_UN) // this will unlock it later
reservations := getReservations(resdb)
var newres []Reservation
var deletedReservation Reservation
found := false
if checkUser {
for _, r := range reservations {
if r.ResName == args[0] && r.Owner != user.Username {
fatalf("You are not the owner of %v", args[0])
}
}
}
for _, r := range reservations {
if r.ResName != args[0] {
newres = append(newres, r)
} else {
deletedReservation = r
found = true
}
}
if !found {
fatalf("Couldn't find reservation %v", args[0])
}
// Truncate the existing reservation file
resdb.Truncate(0)
resdb.Seek(0, 0)
// Write out the new reservations
enc := json.NewEncoder(resdb)
enc.Encode(newres)
resdb.Sync()
// Delete all the PXE files in the reservation
for _, pxename := range deletedReservation.PXENames {
os.Remove(igorConfig.TFTPRoot + "/pxelinux.cfg/" + pxename)
}
}
func (l *layerStore) DoLocked(id string, fn func() error) error {
f, err := os.OpenFile(l.lockPath(id), os.O_CREATE|os.O_RDWR, 0644)
if err != nil {
return err
}
defer os.Remove(f.Name())
defer f.Close()
if err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX); err != nil {
return err
}
defer syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
return fn()
}
func realMain() int {
flag.Parse()
if filesFlag == 0 || directoryFlag == "" {
flag.Usage()
return 1
}
fmt.Println("Creating files...")
var wg sync.WaitGroup
for i := 1; i <= filesFlag; i++ {
wg.Add(1)
go func() {
filename := fmt.Sprintf("%s/%s.lock", directoryFlag, uuid.NewUUID().String())
err := ioutil.WriteFile(filename, []byte("foo"), 0644)
if err != nil {
log.Fatalln(err)
}
wg.Done()
}()
}
wg.Wait()
defer cleanUp()
fmt.Println("Getting all files in " + directoryFlag + "...")
files, err := ioutil.ReadDir(directoryFlag)
if err != nil {
log.Fatalln(err)
}
fmt.Println("Opening all files and applying locks")
for i, file := range files {
fi, err := os.Open(directoryFlag + "/" + file.Name())
if err != nil {
log.Fatalln(err)
}
defer fi.Close()
fd := fi.Fd()
if i%2 == 0 {
syscall.Flock(int(fd), syscall.LOCK_EX|syscall.LOCK_NB)
} else {
syscall.Flock(int(fd), syscall.LOCK_SH)
}
}
time.Sleep(time.Second * 3000)
return 0
}
func TestAcquireRepoLock(t *testing.T) {
// Grab the lock
AcquireRepoLock()
// Now we should be able to open the file (ie. it exists)
lockFile, err := os.Open(lockFilePath)
assert.NoError(t, err)
defer lockFile.Close()
assert.Error(t, syscall.Flock(int(lockFile.Fd()), syscall.LOCK_EX|syscall.LOCK_NB))
// Let it go again
ReleaseRepoLock()
// Now we can get it
assert.NoError(t, syscall.Flock(int(lockFile.Fd()), syscall.LOCK_EX|syscall.LOCK_NB))
// Let it go so the following tests aren't confused :)
assert.NoError(t, syscall.Flock(int(lockFile.Fd()), syscall.LOCK_UN))
}
func (f *FileLock) performLock(flockHow int) (performErr error) {
if f.fileH != nil {
return errors.Newf("FileLock is already acquired!")
}
filePath := path.Join(f.path, f.prefix+f.name)
// GoLang os.OpenFile creates file with FD_CLOEXEC flag already set on it.
// This means file will get closed automatically once the process exits,
// thus we dont need to manually set that flag.
fileH, err := os.Create(filePath)
if err != nil {
return err
}
defer func() {
if performErr != nil {
_ = fileH.Close()
}
}()
if err := syscall.Flock(int(fileH.Fd()), flockHow); err != nil {
return err
}
f.fileH = fileH
return nil
}
// TrySharedLock takes a co-operative (shared) lock without blocking.
// This is idempotent when the Lock already represents a shared lock,
// and tries demote an exclusive lock to shared atomically.
// It will return ErrLocked if an exclusive lock already exists.
func (l *FileLock) TrySharedLock() error {
err := syscall.Flock(l.fd, syscall.LOCK_SH|syscall.LOCK_NB)
if err == syscall.EWOULDBLOCK {
err = ErrLocked
}
return err
}
// TryExclusiveLock takes an exclusive lock without blocking.
// This is idempotent when the Lock already represents an exclusive lock,
// and tries promote a shared lock to exclusive atomically.
// It will return ErrLocked if any lock is already held.
func (l *FileLock) TryExclusiveLock() error {
err := syscall.Flock(l.fd, syscall.LOCK_EX|syscall.LOCK_NB)
if err == syscall.EWOULDBLOCK {
err = ErrLocked
}
return err
}
// PidfileOpen opens new pidfile, locks it, truncates and writes current pid to it
func PidfileOpen(path string) (*Pidfile, error) {
pf, err := pidfileOpenFile(path)
if err != nil {
return nil, err
}
defer func() {
if err != nil {
pf.Close()
}
}()
err = syscall.Flock(int(pf.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
if err != nil {
return nil, fmt.Errorf("flock failed (other process running?): %s, %v", path, err)
}
err = pf.Truncate(0)
if err != nil {
return nil, err
}
_, err = fmt.Fprintf(pf, "%d\n", os.Getpid())
if err != nil {
return nil, err
}
// everything is ok
return &Pidfile{
f: pf,
path: path,
}, nil
}
func GetLock(file *os.File, locktype int) {
fmt.Println("Acquiring lock on ", file.Name())
Info.Println("Acquiring lock on ", file.Name())
syscall.Flock(int(file.Fd()), locktype)
Info.Println("Acquired exclusive lock on ", file.Name())
fmt.Println("Acquired filelock on ", file.Name())
}
// LockWithErr locks a file as exclusively with error handling.
//
// If you use with blocking mode, Lock waits until obtaining a lock.
// Else if you use with non-blocking mode, Lock doesn't wait to obtain a lock (means Lock makes failure immediately if cannot obtain a lock).
func (l *Locker) LockWithErr() error {
if l.file != nil {
return ErrFailedToAcquireLock
}
if l.filename == "" {
return ErrLockFileEmpty
}
var flags int
if l.nonblock {
flags = syscall.LOCK_EX | syscall.LOCK_NB
} else {
flags = syscall.LOCK_EX
}
file, err := os.OpenFile(l.filename, syscall.O_RDWR|syscall.O_NONBLOCK|syscall.O_APPEND|syscall.O_CREAT, 0600) // open append
if err != nil {
return fmt.Errorf("setlock: fatal: unable to open %s: temporary failure", l.filename)
}
defer func() {
if l.file == nil {
// Only close if we failed to flock
file.Close()
}
}()
err = syscall.Flock(int(file.Fd()), flags)
if err != nil {
return ErrFailedToAcquireLock
}
l.file = file
return nil
}
// TryShare is the non-blocking form of Share and will return an error if the
// lock could not be obtained immediately.
func TryShare(file *os.File) error {
lock := syscall.LOCK_SH | syscall.LOCK_NB
if err := syscall.Flock(int(file.Fd()), lock); err != nil {
return err
}
return nil
}
// TryExclusive is the non-blocking form of Exclusive and will return an
// error if the lock could not be obtained immediately.
func TryExclusive(file *os.File) error {
lock := syscall.LOCK_EX | syscall.LOCK_NB
if err := syscall.Flock(int(file.Fd()), lock); err != nil {
return err
}
return nil
}
// CreateLockFile tries to create a file with given name and acquire an
// exclusive lock on it. If the file already exists AND is still locked, it will
// fail.
func CreateLockFile(filename string) (*os.File, error) {
file, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE, 0600)
if err != nil {
return nil, err
}
err = syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
if err != nil {
file.Close()
return nil, err
}
// Write PID to lock file
contents := strconv.Itoa(os.Getpid())
if err := file.Truncate(0); err != nil {
file.Close()
return nil, err
}
if _, err := file.WriteString(contents); err != nil {
file.Close()
return nil, err
}
return file, nil
}
