docker/clonedb/core/locker.py

"""
Lockfile utility

@author: olivier.massot, 05-2020
"""
from path import Path


class AlreadyRunning(RuntimeError):
    pass


def on_error():
    raise AlreadyRunning


class Lockfile:
    """ A lockfile that can be used as a context manager
    """

    def __init__(self, path, on_error=None):
        self.path = Path(path)
        self.on_error = on_error

    def __enter__(self):
        if self.path.exists():
            self.on_error() if self.on_error is not None else on_error()
        self.path.touch()

    def __exit__(self, type, value, traceback):
        self.path.remove()