Source code for sbws.util.filelock
import os
import fcntl
import logging
from sbws.globals import fail_hard
log = logging.getLogger(__name__)
class _FLock:
def __init__(self, lock_fname):
self._lock_fname = lock_fname
self._fd = None
def __enter__(self):
mode = os.O_RDWR | os.O_CREAT | os.O_TRUNC
self._fd = os.open(self._lock_fname, mode)
log.debug('Going to lock %s', self._lock_fname)
try:
fcntl.flock(self._fd, fcntl.LOCK_EX)
except OSError as e:
fail_hard('We couldn\'t call flock. Are you on an unsupported '
'platform? Error: %s', e)
log.debug('Received lock %s', self._lock_fname)
def __exit__(self, exc_type, exc_val, exc_tb):
if self._fd is not None:
log.debug('Releasing lock %s', self._lock_fname)
os.close(self._fd)
[docs]class DirectoryLock(_FLock):
'''
Holds a lock on a file in **dname** so that other sbws processes/threads
won't try to read/write while we are reading/writing in this directory.
>>> with DirectoryLock(dname):
>>> # do some reading/writing in dname
>>> # no longer have the lock
Note: The directory must already exist.
:param str dname: Name of directory for which we want to obtain a lock
'''
def __init__(self, dname):
assert os.path.isdir(dname)
lock_fname = os.path.join(dname, '.lockfile')
super().__init__(lock_fname)
[docs]class FileLock(_FLock):
'''
Holds a lock on **fname** so that other sbws processes/threads
won't try to read/write while we are reading/writing this file.
>>> with FileLock(fname):
>>> # do some reading/writing of fname
>>> # no longer have the lock
:param str fname: Name of the file for which we want to obtain a lock
'''
def __init__(self, fname):
lock_fname = fname + '.lockfile'
super().__init__(lock_fname)