File size: 7,545 Bytes
3a5cf48 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 | """Async wrapper around :class:`ReadWriteLock` for use with ``asyncio``."""
from __future__ import annotations
import asyncio
import functools
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._executor = executor
@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)
__all__ = [
"AsyncAcquireReadWriteReturnProxy",
"AsyncReadWriteLock",
]
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