Python fcntl.lockf() Examples

def release(self):
        """Release the lock by deleting `self.lockfile`."""
        if not self._lock.is_set():
            return False

        try:
            fcntl.lockf(self._lockfile, fcntl.LOCK_UN)
        except IOError:  # pragma: no cover
            pass
        finally:
            self._lock.clear()
            self._lockfile = None
            try:
                os.unlink(self.lockfile)
            except (IOError, OSError):  # pragma: no cover
                pass

            return True 

def bounce_lock(name):
    """Acquire a bounce lockfile for the name given. The name should generally
    be the service namespace being bounced.

    This is a contextmanager. Please use it via 'with bounce_lock(name):'.

    :param name: The lock name to acquire"""
    lockfile = "/var/lock/%s.lock" % name
    with open(lockfile, "w") as fd:
        remove = False
        try:
            fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
            remove = True
            yield
        except IOError:
            raise LockHeldException("Service %s is already being bounced!" % name)
        finally:
            if remove:
                os.remove(lockfile) 

def singleton(lockfile, text="semaphore"):
    """
    Open a lockfile exclusively.
    """

    if not lockfile.parent.exists():
        mkdir(lockfile.parent)

    try:
        if has_fcntl:
            f = open(lockfile, "w")
            fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
        else:
            if lockfile.exists():
                lockfile.unlink()
            fd = os.open(lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
            f = open(fd, "w")
        f.write(text)
    except IOError:
        return None
    return f 

def lock(self):
        """
        Locks the package to avoid concurrent operations on its shared
        resources.
        Currently, the only resource shared among scripts executed from
        different directories is the repository.
        """
        if not self.locking_enabled:
            LOG.debug("This package has no shared resources to lock")
            return

        LOG.debug("Checking for lock on file {}.".format(self.lock_file_path))
        self.lock_file = open(self.lock_file_path, "w")
        try:
            fcntl.lockf(self.lock_file, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except IOError as exc:
            RESOURCE_UNAVAILABLE_ERROR = 11
            if exc.errno == RESOURCE_UNAVAILABLE_ERROR:
                LOG.info("Waiting for other process to finish operations "
                         "on {}.".format(self.name))
            else:
                raise
        fcntl.lockf(self.lock_file, fcntl.LOCK_EX) 

def release(self):
        """Release the lock by deleting `self.lockfile`."""
        if not self._lock.is_set():
            return False

        try:
            fcntl.lockf(self._lockfile, fcntl.LOCK_UN)
        except IOError:  # pragma: no cover
            pass
        finally:
            self._lock.clear()
            self._lockfile = None
            try:
                os.unlink(self.lockfile)
            except (IOError, OSError):  # pragma: no cover
                pass

            return True 

def __init__(self, client_name):
        self.lockfile = os.path.join(get_cache_dir("client_locks"), client_name)
        logger.debug("SingleInstance lockfile: " + self.lockfile)
        if sys.platform == 'win32':
            try:
                # file already exists, we try to remove (in case previous execution was interrupted)
                if os.path.exists(self.lockfile):
                    os.unlink(self.lockfile)
                    self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
            except OSError as e:
                if e.errno == 13:
                    logger.error("Another instance is already running, quitting.")
                    sys.exit(-1)
                else:
                    raise e
        else:  # non Windows
            self.fp = open(self.lockfile, 'w')
            try:
                fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
            except IOError:
                logger.error("Another instance is already running, quitting.")
                sys.exit(-1) 

def unlock_file(self, name):
        f = self.locks.get(name)
        if not f:
            self.log(DEBUG, "unlock_file: %s not locked", name)
            return

        # XXXX does this create a possible race condition?
        if 0:
            try:
                os.unlink(name)
            except:
                pass
        status = fcntl.lockf(f, fcntl.LOCK_UN)
        f.close()
        del self.locks[name]
        return status 

def release(self):
        """Release the lock by deleting `self.lockfile`."""
        if not self._lock.is_set():
            return False

        try:
            fcntl.lockf(self._lockfile, fcntl.LOCK_UN)
        except IOError:  # pragma: no cover
            pass
        finally:
            self._lock.clear()
            self._lockfile = None
            try:
                os.unlink(self.lockfile)
            except (IOError, OSError):  # pragma: no cover
                pass

            return True 

def lock():
    # Since Local Mode uses the same port for serving, we need a lock in order
    # to allow concurrent test execution.
    local_mode_lock_fd = open(LOCK_PATH, 'w')
    local_mode_lock = local_mode_lock_fd.fileno()

    fcntl.lockf(local_mode_lock, fcntl.LOCK_EX)

    try:
        yield
    finally:
        time.sleep(5)
        fcntl.lockf(local_mode_lock, fcntl.LOCK_UN) 

def _rootCacheUnlock(self):
        fcntl.lockf(self.rootCacheLock.fileno(), fcntl.LOCK_UN) 

def _rootCacheLock(self, shared=1):
        lockType = fcntl.LOCK_EX
        if shared:
            lockType = fcntl.LOCK_SH
        try:
            fcntl.lockf(self.rootCacheLock.fileno(), lockType | fcntl.LOCK_NB)
        except IOError:
            self.state.start("Waiting for rootcache lock")
            fcntl.lockf(self.rootCacheLock.fileno(), lockType)
            self.state.finish("Waiting for rootcache lock") 

def write_pid_file(pid_file, pid):
    import fcntl
    import stat

    try:
        fd = os.open(pid_file, os.O_RDWR | os.O_CREAT,
                     stat.S_IRUSR | stat.S_IWUSR)
    except OSError as e:
        shell.print_exception(e)
        return -1
    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
    assert flags != -1
    flags |= fcntl.FD_CLOEXEC
    r = fcntl.fcntl(fd, fcntl.F_SETFD, flags)
    assert r != -1
    # There is no platform independent way to implement fcntl(fd, F_SETLK, &fl)
    # via fcntl.fcntl. So use lockf instead
    try:
        fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB, 0, 0, os.SEEK_SET)
    except IOError:
        r = os.read(fd, 32)
        if r:
            logging.error('already started at pid %s' % common.to_str(r))
        else:
            logging.error('already started')
        os.close(fd)
        return -1
    os.ftruncate(fd, 0)
    os.write(fd, common.to_bytes(str(pid)))
    return 0 

def single_instance_unix(name: str) -> bool:
    import socket
    for path in unix_socket_paths(name):
        socket_path = path.rpartition('.')[0] + '.sock'
        fd = os.open(path, os.O_CREAT | os.O_WRONLY | os.O_TRUNC | os.O_CLOEXEC)
        try:
            fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except OSError as err:
            if err.errno in (errno.EAGAIN, errno.EACCES):
                # Client
                s = socket.socket(family=socket.AF_UNIX)
                s.connect(socket_path)
                single_instance.socket = s
                return False
            raise
        s = socket.socket(family=socket.AF_UNIX)
        try:
            s.bind(socket_path)
        except OSError as err:
            if err.errno in (errno.EADDRINUSE, errno.EEXIST):
                os.unlink(socket_path)
                s.bind(socket_path)
            else:
                raise
        single_instance.socket = s  # prevent garbage collection from closing the socket
        atexit.register(remove_socket_file, s, socket_path)
        s.listen()
        s.set_inheritable(False)
        return True
    return False 

def unlock(self):
        """
        Unlocks the package to allow other processes to operate on its
        shared resources.
        """
        if not self.locking_enabled:
            return

        LOG.debug("Unlocking file {}".format(self.lock_file_path))
        fcntl.lockf(self.lock_file, fcntl.LOCK_UN)
        self.lock_file.close() 

def write_pid_file(pid_file, pid):
    import fcntl
    import stat

    try:
        fd = os.open(pid_file, os.O_RDWR | os.O_CREAT,
                     stat.S_IRUSR | stat.S_IWUSR)
    except OSError as e:
        shell.print_exception(e)
        return -1
    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
    assert flags != -1
    flags |= fcntl.FD_CLOEXEC
    r = fcntl.fcntl(fd, fcntl.F_SETFD, flags)
    assert r != -1
    # There is no platform independent way to implement fcntl(fd, F_SETLK, &fl)
    # via fcntl.fcntl. So use lockf instead
    try:
        fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB, 0, 0, os.SEEK_SET)
    except IOError:
        r = os.read(fd, 32)
        if r:
            logging.error('already started at pid %s' % common.to_str(r))
        else:
            logging.error('already started')
        os.close(fd)
        return -1
    os.ftruncate(fd, 0)
    os.write(fd, common.to_bytes(str(pid)))
    return 0 

def _set_locked(self, locked):
        if not self._use_locking:
            return
        import fcntl
        if locked:
            fcntl.lockf(self._file_desc, fcntl.LOCK_EX)
        else:
            fcntl.lockf(self._file_desc, fcntl.LOCK_UN) 

def release(self):
        """Release the lock"""
        if self.lock_file:
            if fcntl:
                fcntl.lockf(self.lock_file, fcntl.LOCK_UN)
            self.lock_file.close()
            self.lock_file = None 

def write_pid_file(pid_file, pid):
    import fcntl
    import stat

    try:
        fd = os.open(pid_file, os.O_RDWR | os.O_CREAT,
                     stat.S_IRUSR | stat.S_IWUSR)
    except OSError as e:
        shell.print_exception(e)
        return -1
    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
    assert flags != -1
    flags |= fcntl.FD_CLOEXEC
    r = fcntl.fcntl(fd, fcntl.F_SETFD, flags)
    assert r != -1
    # There is no platform independent way to implement fcntl(fd, F_SETLK, &fl)
    # via fcntl.fcntl. So use lockf instead
    try:
        fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB, 0, 0, os.SEEK_SET)
    except IOError:
        r = os.read(fd, 32)
        if r:
            logging.error('already started at pid %s' % common.to_str(r))
        else:
            logging.error('already started')
        os.close(fd)
        return -1
    os.ftruncate(fd, 0)
    os.write(fd, common.to_bytes(str(pid)))
    return 0 

def _unlock_file(f):
    """Unlock file f using lockf and dot locking."""
    if fcntl:
        fcntl.lockf(f, fcntl.LOCK_UN)
    if os.path.exists(f.name + '.lock'):
        os.remove(f.name + '.lock') 

def _lock_file(f, dotlock=True):
    """Lock file f using lockf and dot locking."""
    dotlock_done = False
    try:
        if fcntl:
            try:
                fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
            except OSError as e:
                if e.errno in (errno.EAGAIN, errno.EACCES, errno.EROFS):
                    raise ExternalClashError('lockf: lock unavailable: %s' %
                                             f.name)
                else:
                    raise
        if dotlock:
            try:
                pre_lock = _create_temporary(f.name + '.lock')
                pre_lock.close()
            except OSError as e:
                if e.errno in (errno.EACCES, errno.EROFS):
                    return  # Without write access, just skip dotlocking.
                else:
                    raise
            try:
                if hasattr(os, 'link'):
                    os.link(pre_lock.name, f.name + '.lock')
                    dotlock_done = True
                    os.unlink(pre_lock.name)
                else:
                    os.rename(pre_lock.name, f.name + '.lock')
                    dotlock_done = True
            except FileExistsError:
                os.remove(pre_lock.name)
                raise ExternalClashError('dot lock unavailable: %s' %
                                         f.name)
    except:
        if fcntl:
            fcntl.lockf(f, fcntl.LOCK_UN)
        if dotlock_done:
            os.remove(f.name + '.lock')
        raise 

def release(self, path, fh):
        fcntl.lockf(fh, fcntl.LOCK_UN) 

def lock(self, path, fh, cmd, lock):
        fcntl.lockf(fh, fcntl.LOCK_EX) 

def unlock_and_close(self):
        """Close and unlock the file using the fcntl.lockf primitive."""
        if self._locked:
            fcntl.lockf(self._fh.fileno(), fcntl.LOCK_UN)
        self._locked = False
        if self._fh:
            self._fh.close() 

def flock_release(fd):
    ''' Release lock so next snapshots can continue '''

    fcntl.lockf(fd, fcntl.LOCK_UN)
    os.close(fd)
    os.remove(cfg['lock_file']) 

def flock_exclusive():
    ''' lock so only one snapshot of current config is running '''
    fd = os.open(cfg['lock_file'], os.O_CREAT | os.O_TRUNC | os.O_WRONLY, 0600)
    try:
        fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
    except IOError:
        return False
    return fd 

def __exit__(self, type, value, tb): # pylint: disable=redefined-builtin
        """Exit RunSingleInstance class
        :return: None
        """
        try:
            if not self.__is_running:
                fcntl.lockf(self.__filelock, fcntl.LOCK_UN)
                self.__filelock.close()
                os.unlink(self.__lockfile)
        except Exception as err:
            logger.error("Error unlocking single instance file", error=err.message) 

def __enter__(self):
        """Enter RunSingleInstance class
        :return: self
        """
        self.__checked = True

        try:
            self.__filelock = open(self.__lockfile, 'w+')
            # None blocking lock
            fcntl.lockf(self.__filelock, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except IOError:
            if self.__filelock is not None:
                self.__is_running = True
        return self 

def write_pid_file(pid_file, pid):
    import fcntl
    import stat

    try:
        fd = os.open(pid_file, os.O_RDWR | os.O_CREAT,
                     stat.S_IRUSR | stat.S_IWUSR)
    except OSError as e:
        shell.print_exception(e)
        return -1
    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
    assert flags != -1
    flags |= fcntl.FD_CLOEXEC
    r = fcntl.fcntl(fd, fcntl.F_SETFD, flags)
    assert r != -1
    # There is no platform independent way to implement fcntl(fd, F_SETLK, &fl)
    # via fcntl.fcntl. So use lockf instead
    try:
        fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB, 0, 0, os.SEEK_SET)
    except IOError:
        r = os.read(fd, 32)
        if r:
            logging.error('already started at pid %s' % common.to_str(r))
        else:
            logging.error('already started')
        os.close(fd)
        return -1
    os.ftruncate(fd, 0)
    os.write(fd, common.to_bytes(str(pid)))
    return 0 

def _lock(self, flag, length, start, whence):
        fcntl.lockf(self.fileno(), flag, length, start, whence) 

def unlock_and_close(self):
        """Close and unlock the file using the fcntl.lockf primitive."""
        if self._locked:
            fcntl.lockf(self._fh.fileno(), fcntl.LOCK_UN)
        self._locked = False
        if self._fh:
            self._fh.close()