workflow.py 文件源码

def acquire(self, blocking=True):
        """Acquire the lock if possible.

        If the lock is in use and ``blocking`` is ``False``, return
        ``False``.

        Otherwise, check every `self.delay` seconds until it acquires
        lock or exceeds `self.timeout` and raises an `~AcquisitionError`.

        """
        start = time.time()
        while True:

            self._validate_lockfile()

            try:
                fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
                with os.fdopen(fd, 'w') as fd:
                    fd.write('{0}'.format(os.getpid()))
                break
            except OSError as err:
                if err.errno != errno.EEXIST:  # pragma: no cover
                    raise

                if self.timeout and (time.time() - start) >= self.timeout:
                    raise AcquisitionError('Lock acquisition timed out.')
                if not blocking:
                    return False
                time.sleep(self.delay)

        self._locked = True
        return True