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315 lines
11 KiB
315 lines
11 KiB
"""An asyncio-based implementation of the file lock."""
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from __future__ import annotations
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import asyncio
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import contextlib
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import logging
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import os
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import time
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from dataclasses import dataclass
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from threading import local
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from typing import TYPE_CHECKING, Any, Callable, NoReturn
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from ._api import BaseFileLock, FileLockContext
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from ._error import Timeout
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from ._soft import SoftFileLock
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from ._unix import UnixFileLock
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from ._windows import WindowsFileLock
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if TYPE_CHECKING:
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import sys
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from concurrent import futures
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from types import TracebackType
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if sys.version_info >= (3, 11): # pragma: no cover (py311+)
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from typing import Self
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else: # pragma: no cover (<py311)
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from typing_extensions import Self
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_LOGGER = logging.getLogger("filelock")
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@dataclass
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class AsyncFileLockContext(FileLockContext):
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"""A dataclass which holds the context for a ``BaseAsyncFileLock`` object."""
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#: Whether run in executor
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run_in_executor: bool = True
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#: The executor
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executor: futures.Executor | None = None
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#: The loop
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loop: asyncio.AbstractEventLoop | None = None
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class AsyncThreadLocalFileContext(AsyncFileLockContext, local):
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"""A thread local version of the ``FileLockContext`` class."""
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class AsyncAcquireReturnProxy:
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"""A context-aware object that will release the lock file when exiting."""
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def __init__(self, lock: BaseAsyncFileLock) -> None: # noqa: D107
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self.lock = lock
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async def __aenter__(self) -> BaseAsyncFileLock: # noqa: D105
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return self.lock
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async def __aexit__( # noqa: D105
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self,
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exc_type: type[BaseException] | None,
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exc_value: BaseException | None,
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traceback: TracebackType | None,
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) -> None:
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await self.lock.release()
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class BaseAsyncFileLock(BaseFileLock):
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"""Base class for asynchronous file locks."""
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def __init__( # noqa: PLR0913
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self,
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lock_file: str | os.PathLike[str],
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timeout: float = -1,
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mode: int = 0o644,
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thread_local: bool = False, # noqa: FBT001, FBT002
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*,
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blocking: bool = True,
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is_singleton: bool = False,
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loop: asyncio.AbstractEventLoop | None = None,
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run_in_executor: bool = True,
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executor: futures.Executor | None = None,
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) -> None:
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"""
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Create a new lock object.
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:param lock_file: path to the file
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:param timeout: default timeout when acquiring the lock, in seconds. It will be used as fallback value in \
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the acquire method, if no timeout value (``None``) is given. If you want to disable the timeout, set it \
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to a negative value. A timeout of 0 means that there is exactly one attempt to acquire the file lock.
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:param mode: file permissions for the lockfile
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:param thread_local: Whether this object's internal context should be thread local or not. If this is set to \
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``False`` then the lock will be reentrant across threads.
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:param blocking: whether the lock should be blocking or not
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:param is_singleton: If this is set to ``True`` then only one instance of this class will be created \
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per lock file. This is useful if you want to use the lock object for reentrant locking without needing \
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to pass the same object around.
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:param loop: The event loop to use. If not specified, the running event loop will be used.
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:param run_in_executor: If this is set to ``True`` then the lock will be acquired in an executor.
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:param executor: The executor to use. If not specified, the default executor will be used.
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"""
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self._is_thread_local = thread_local
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self._is_singleton = is_singleton
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if thread_local and run_in_executor:
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msg = "run_in_executor is not supported when thread_local is True"
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raise ValueError(msg)
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# Create the context. Note that external code should not work with the context directly and should instead use
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# properties of this class.
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kwargs: dict[str, Any] = {
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"lock_file": os.fspath(lock_file),
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"timeout": timeout,
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"mode": mode,
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"blocking": blocking,
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"loop": loop,
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"run_in_executor": run_in_executor,
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"executor": executor,
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}
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self._context: AsyncFileLockContext = (AsyncThreadLocalFileContext if thread_local else AsyncFileLockContext)(
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**kwargs
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)
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@property
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def run_in_executor(self) -> bool:
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"""::return: whether run in executor."""
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return self._context.run_in_executor
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@property
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def executor(self) -> futures.Executor | None:
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"""::return: the executor."""
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return self._context.executor
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@executor.setter
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def executor(self, value: futures.Executor | None) -> None: # pragma: no cover
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"""
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Change the executor.
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:param value: the new executor or ``None``
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:type value: futures.Executor | None
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"""
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self._context.executor = value
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@property
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def loop(self) -> asyncio.AbstractEventLoop | None:
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"""::return: the event loop."""
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return self._context.loop
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async def acquire( # type: ignore[override]
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self,
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timeout: float | None = None,
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poll_interval: float = 0.05,
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*,
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blocking: bool | None = None,
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) -> AsyncAcquireReturnProxy:
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"""
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Try to acquire the file lock.
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:param timeout: maximum wait time for acquiring the lock, ``None`` means use the default
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:attr:`~BaseFileLock.timeout` is and if ``timeout < 0``, there is no timeout and
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this method will block until the lock could be acquired
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:param poll_interval: interval of trying to acquire the lock file
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:param blocking: defaults to True. If False, function will return immediately if it cannot obtain a lock on the
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first attempt. Otherwise, this method will block until the timeout expires or the lock is acquired.
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:raises Timeout: if fails to acquire lock within the timeout period
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:return: a context object that will unlock the file when the context is exited
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.. code-block:: python
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# You can use this method in the context manager (recommended)
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with lock.acquire():
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pass
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# Or use an equivalent try-finally construct:
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lock.acquire()
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try:
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pass
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finally:
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lock.release()
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"""
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# Use the default timeout, if no timeout is provided.
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if timeout is None:
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timeout = self._context.timeout
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if blocking is None:
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blocking = self._context.blocking
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# Increment the number right at the beginning. We can still undo it, if something fails.
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self._context.lock_counter += 1
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lock_id = id(self)
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lock_filename = self.lock_file
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start_time = time.perf_counter()
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try:
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while True:
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if not self.is_locked:
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_LOGGER.debug("Attempting to acquire lock %s on %s", lock_id, lock_filename)
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await self._run_internal_method(self._acquire)
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if self.is_locked:
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_LOGGER.debug("Lock %s acquired on %s", lock_id, lock_filename)
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break
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if blocking is False:
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_LOGGER.debug("Failed to immediately acquire lock %s on %s", lock_id, lock_filename)
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raise Timeout(lock_filename) # noqa: TRY301
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if 0 <= timeout < time.perf_counter() - start_time:
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_LOGGER.debug("Timeout on acquiring lock %s on %s", lock_id, lock_filename)
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raise Timeout(lock_filename) # noqa: TRY301
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msg = "Lock %s not acquired on %s, waiting %s seconds ..."
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_LOGGER.debug(msg, lock_id, lock_filename, poll_interval)
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await asyncio.sleep(poll_interval)
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except BaseException: # Something did go wrong, so decrement the counter.
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self._context.lock_counter = max(0, self._context.lock_counter - 1)
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raise
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return AsyncAcquireReturnProxy(lock=self)
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async def release(self, force: bool = False) -> None: # type: ignore[override] # noqa: FBT001, FBT002
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"""
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Releases the file lock. Please note, that the lock is only completely released, if the lock counter is 0.
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Also note, that the lock file itself is not automatically deleted.
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:param force: If true, the lock counter is ignored and the lock is released in every case/
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"""
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if self.is_locked:
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self._context.lock_counter -= 1
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if self._context.lock_counter == 0 or force:
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lock_id, lock_filename = id(self), self.lock_file
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_LOGGER.debug("Attempting to release lock %s on %s", lock_id, lock_filename)
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await self._run_internal_method(self._release)
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self._context.lock_counter = 0
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_LOGGER.debug("Lock %s released on %s", lock_id, lock_filename)
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async def _run_internal_method(self, method: Callable[[], Any]) -> None:
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if asyncio.iscoroutinefunction(method):
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await method()
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elif self.run_in_executor:
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loop = self.loop or asyncio.get_running_loop()
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await loop.run_in_executor(self.executor, method)
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else:
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method()
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def __enter__(self) -> NoReturn:
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"""
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Replace old __enter__ method to avoid using it.
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NOTE: DO NOT USE `with` FOR ASYNCIO LOCKS, USE `async with` INSTEAD.
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:return: none
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:rtype: NoReturn
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"""
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msg = "Do not use `with` for asyncio locks, use `async with` instead."
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raise NotImplementedError(msg)
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async def __aenter__(self) -> Self:
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"""
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Acquire the lock.
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:return: the lock object
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"""
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await self.acquire()
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return self
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async def __aexit__(
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self,
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exc_type: type[BaseException] | None,
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exc_value: BaseException | None,
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traceback: TracebackType | None,
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) -> None:
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"""
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Release the lock.
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:param exc_type: the exception type if raised
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:param exc_value: the exception value if raised
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:param traceback: the exception traceback if raised
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"""
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await self.release()
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def __del__(self) -> None:
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"""Called when the lock object is deleted."""
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with contextlib.suppress(RuntimeError):
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loop = self.loop or asyncio.get_running_loop()
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if not loop.is_running(): # pragma: no cover
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loop.run_until_complete(self.release(force=True))
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else:
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loop.create_task(self.release(force=True))
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class AsyncSoftFileLock(SoftFileLock, BaseAsyncFileLock):
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"""Simply watches the existence of the lock file."""
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class AsyncUnixFileLock(UnixFileLock, BaseAsyncFileLock):
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"""Uses the :func:`fcntl.flock` to hard lock the lock file on unix systems."""
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class AsyncWindowsFileLock(WindowsFileLock, BaseAsyncFileLock):
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"""Uses the :func:`msvcrt.locking` to hard lock the lock file on windows systems."""
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__all__ = [
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"AsyncAcquireReturnProxy",
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"AsyncSoftFileLock",
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"AsyncUnixFileLock",
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"AsyncWindowsFileLock",
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"BaseAsyncFileLock",
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]
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