"""holds locking functionality that works across processes."""
from __future__ import annotations
import logging
import os
from abc import ABC, abstractmethod
from contextlib import contextmanager, suppress
from pathlib import Path
from threading import Lock, RLock
from filelock import FileLock, Timeout
LOGGER = logging.getLogger(__name__)
class _CountedFileLock(FileLock):
def __init__(self, lock_file) -> None:
parent = os.path.dirname(lock_file)
if not os.path.isdir(parent):
with suppress(OSError):
os.makedirs(parent)
super().__init__(lock_file)
self.count = 0
self.thread_safe = RLock()
def acquire(self, timeout=None, poll_interval=0.05):
if not self.thread_safe.acquire(timeout=-1 if timeout is None else timeout):
raise Timeout(self.lock_file)
if self.count == 0:
super().acquire(timeout, poll_interval)
self.count += 1
def release(self, force=False): # noqa: FBT002
with self.thread_safe:
if self.count > 0:
self.thread_safe.release()
if self.count == 1:
super().release(force=force)
self.count = max(self.count - 1, 0)
_lock_store = {}
_store_lock = Lock()
class PathLockBase(ABC):
def __init__(self, folder) -> None:
path = Path(folder)
self.path = path.resolve() if path.exists() else path
def __repr__(self) -> str:
return f"{self.__class__.__name__}({self.path})"
def __truediv__(self, other):
return type(self)(self.path / other)
@abstractmethod
def __enter__(self):
raise NotImplementedError
@abstractmethod
def __exit__(self, exc_type, exc_val, exc_tb):
raise NotImplementedError
@abstractmethod
@contextmanager
def lock_for_key(self, name, no_block=False): # noqa: FBT002
raise NotImplementedError
@abstractmethod
@contextmanager
def non_reentrant_lock_for_key(self, name):
raise NotImplementedError
class ReentrantFileLock(PathLockBase):
def __init__(self, folder) -> None:
super().__init__(folder)
self._lock = None
def _create_lock(self, name=""):
lock_file = str(self.path / f"{name}.lock")
with _store_lock:
if lock_file not in _lock_store:
_lock_store[lock_file] = _CountedFileLock(lock_file)
return _lock_store[lock_file]
@staticmethod
def _del_lock(lock):
if lock is not None:
with _store_lock, lock.thread_safe:
if lock.count == 0:
_lock_store.pop(lock.lock_file, None)
def __del__(self) -> None:
self._del_lock(self._lock)
def __enter__(self):
self._lock = self._create_lock()
self._lock_file(self._lock)
def __exit__(self, exc_type, exc_val, exc_tb):
self._release(self._lock)
self._del_lock(self._lock)
self._lock = None
def _lock_file(self, lock, no_block=False): # noqa: FBT002
# multiple processes might be trying to get a first lock... so we cannot check if this directory exist without
# a lock, but that lock might then become expensive, and it's not clear where that lock should live.
# Instead here we just ignore if we fail to create the directory.
with suppress(OSError):
os.makedirs(str(self.path))
try:
lock.acquire(0.0001)
except Timeout:
if no_block:
raise
LOGGER.debug("lock file %s present, will block until released", lock.lock_file)
lock.release() # release the acquire try from above
lock.acquire()
@staticmethod
def _release(lock):
lock.release()
@contextmanager
def lock_for_key(self, name, no_block=False): # noqa: FBT002
lock = self._create_lock(name)
try:
try:
self._lock_file(lock, no_block)
yield
finally:
self._release(lock)
finally:
self._del_lock(lock)
lock = None
@contextmanager
def non_reentrant_lock_for_key(self, name):
with _CountedFileLock(str(self.path / f"{name}.lock")):
yield
class NoOpFileLock(PathLockBase):
def __enter__(self):
raise NotImplementedError
def __exit__(self, exc_type, exc_val, exc_tb):
raise NotImplementedError
@contextmanager
def lock_for_key(self, name, no_block=False): # noqa: ARG002, FBT002
yield
@contextmanager
def non_reentrant_lock_for_key(self, name): # noqa: ARG002
yield
__all__ = [
"NoOpFileLock",
"ReentrantFileLock",
"Timeout",
]
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