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python3.10
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filelock
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Filename :
_async_read_write.py
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"""Async wrapper around :class:`ReadWriteLock` for use with ``asyncio``.""" from __future__ import annotations import asyncio import functools from concurrent.futures import ThreadPoolExecutor from contextlib import asynccontextmanager from typing import TYPE_CHECKING from ._read_write import ReadWriteLock if TYPE_CHECKING: import os from collections.abc import AsyncGenerator, Callable from concurrent import futures from types import TracebackType class AsyncAcquireReadWriteReturnProxy: """Context-aware object that releases the async read/write lock on exit.""" def __init__(self, lock: AsyncReadWriteLock) -> None: self.lock = lock async def __aenter__(self) -> AsyncReadWriteLock: return self.lock async def __aexit__( self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None, ) -> None: await self.lock.release() class AsyncReadWriteLock: """ Async wrapper around :class:`ReadWriteLock` for use in ``asyncio`` applications. Because Python's :mod:`sqlite3` module has no async API, all blocking SQLite operations are dispatched to a thread pool via ``loop.run_in_executor()``. Reentrancy, upgrade/downgrade rules, and singleton behavior are delegated to the underlying :class:`ReadWriteLock`. :param lock_file: path to the SQLite database file used as the lock :param timeout: maximum wait time in seconds; ``-1`` means block indefinitely :param blocking: if ``False``, raise :class:`~filelock.Timeout` immediately when the lock is unavailable :param is_singleton: if ``True``, reuse existing :class:`ReadWriteLock` instances for the same resolved path :param loop: event loop for ``run_in_executor``; ``None`` uses the running loop :param executor: executor for ``run_in_executor``; ``None`` uses the default executor .. versionadded:: 3.21.0 """ def __init__( # noqa: PLR0913 self, lock_file: str | os.PathLike[str], timeout: float = -1, *, blocking: bool = True, is_singleton: bool = True, loop: asyncio.AbstractEventLoop | None = None, executor: futures.Executor | None = None, ) -> None: self._lock = ReadWriteLock(lock_file, timeout, blocking=blocking, is_singleton=is_singleton) self._loop = loop self._owns_executor = executor is None self._executor = executor or ThreadPoolExecutor(max_workers=1) @property def lock_file(self) -> str: """:returns: the path to the lock file.""" return self._lock.lock_file @property def timeout(self) -> float: """:returns: the default timeout.""" return self._lock.timeout @property def blocking(self) -> bool: """:returns: whether blocking is enabled by default.""" return self._lock.blocking @property def loop(self) -> asyncio.AbstractEventLoop | None: """:returns: the event loop (or ``None`` for the running loop).""" return self._loop @property def executor(self) -> futures.Executor | None: """:returns: the executor (or ``None`` for the default).""" return self._executor async def _run(self, func: Callable[..., object], *args: object, **kwargs: object) -> object: loop = self._loop or asyncio.get_running_loop() return await loop.run_in_executor(self._executor, functools.partial(func, *args, **kwargs)) async def acquire_read(self, timeout: float = -1, *, blocking: bool = True) -> AsyncAcquireReadWriteReturnProxy: """ Acquire a shared read lock. See :meth:`ReadWriteLock.acquire_read` for full semantics. :param timeout: maximum wait time in seconds; ``-1`` means block indefinitely :param blocking: if ``False``, raise :class:`~filelock.Timeout` immediately when the lock is unavailable :returns: a proxy that can be used as an async context manager to release the lock :raises RuntimeError: if a write lock is already held on this instance :raises Timeout: if the lock cannot be acquired within *timeout* seconds """ await self._run(self._lock.acquire_read, timeout, blocking=blocking) return AsyncAcquireReadWriteReturnProxy(lock=self) async def acquire_write(self, timeout: float = -1, *, blocking: bool = True) -> AsyncAcquireReadWriteReturnProxy: """ Acquire an exclusive write lock. See :meth:`ReadWriteLock.acquire_write` for full semantics. :param timeout: maximum wait time in seconds; ``-1`` means block indefinitely :param blocking: if ``False``, raise :class:`~filelock.Timeout` immediately when the lock is unavailable :returns: a proxy that can be used as an async context manager to release the lock :raises RuntimeError: if a read lock is already held, or a write lock is held by a different thread :raises Timeout: if the lock cannot be acquired within *timeout* seconds """ await self._run(self._lock.acquire_write, timeout, blocking=blocking) return AsyncAcquireReadWriteReturnProxy(lock=self) async def release(self, *, force: bool = False) -> None: """ Release one level of the current lock. See :meth:`ReadWriteLock.release` for full semantics. :param force: if ``True``, release the lock completely regardless of the current lock level :raises RuntimeError: if no lock is currently held and *force* is ``False`` """ await self._run(self._lock.release, force=force) @asynccontextmanager async def read_lock(self, timeout: float | None = None, *, blocking: bool | None = None) -> AsyncGenerator[None]: """ Async context manager that acquires and releases a shared read lock. Falls back to instance defaults for *timeout* and *blocking* when ``None``. :param timeout: maximum wait time in seconds, or ``None`` to use the instance default :param blocking: if ``False``, raise :class:`~filelock.Timeout` immediately; ``None`` uses the instance default """ if timeout is None: timeout = self._lock.timeout if blocking is None: blocking = self._lock.blocking await self.acquire_read(timeout, blocking=blocking) try: yield finally: await self.release() @asynccontextmanager async def write_lock(self, timeout: float | None = None, *, blocking: bool | None = None) -> AsyncGenerator[None]: """ Async context manager that acquires and releases an exclusive write lock. Falls back to instance defaults for *timeout* and *blocking* when ``None``. :param timeout: maximum wait time in seconds, or ``None`` to use the instance default :param blocking: if ``False``, raise :class:`~filelock.Timeout` immediately; ``None`` uses the instance default """ if timeout is None: timeout = self._lock.timeout if blocking is None: blocking = self._lock.blocking await self.acquire_write(timeout, blocking=blocking) try: yield finally: await self.release() async def close(self) -> None: """ Release the lock (if held) and close the underlying SQLite connection. After calling this method, the lock instance is no longer usable. """ await self._run(self._lock.close) if self._owns_executor: self._executor.shutdown(wait=False) __all__ = [ "AsyncAcquireReadWriteReturnProxy", "AsyncReadWriteLock", ]