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84 lines
2.5 KiB
Python
84 lines
2.5 KiB
Python
"""Python threading tools."""
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from __future__ import annotations
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import collections.abc as c
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import contextlib
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import functools
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import sys
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import threading
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import queue
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import typing as t
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TCallable = t.TypeVar('TCallable', bound=t.Callable[..., t.Any])
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class WrappedThread(threading.Thread):
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"""Wrapper around Thread which captures results and exceptions."""
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def __init__(self, action: c.Callable[[], t.Any]) -> None:
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super().__init__()
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self._result: queue.Queue[t.Any] = queue.Queue()
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self.action = action
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self.result = None
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def run(self) -> None:
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"""
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Run action and capture results or exception.
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Do not override. Do not call directly. Executed by the start() method.
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"""
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# We truly want to catch anything that the worker thread might do including call sys.exit.
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# Therefore, we catch *everything* (including old-style class exceptions)
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# noinspection PyBroadException
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try:
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self._result.put((self.action(), None))
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# pylint: disable=locally-disabled, bare-except
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except: # noqa
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self._result.put((None, sys.exc_info()))
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def wait_for_result(self) -> t.Any:
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"""Wait for thread to exit and return the result or raise an exception."""
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result, exception = self._result.get()
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if exception:
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raise exception[1].with_traceback(exception[2])
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self.result = result
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return result
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def mutex(func: TCallable) -> TCallable:
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"""Enforce exclusive access on a decorated function."""
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lock = threading.Lock()
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@functools.wraps(func)
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def wrapper(*args, **kwargs):
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"""Wrapper around `func` which uses a lock to provide exclusive access to the function."""
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with lock:
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return func(*args, **kwargs)
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return wrapper # type: ignore[return-value] # requires https://www.python.org/dev/peps/pep-0612/ support
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__named_lock = threading.Lock()
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__named_locks: dict[str, threading.Lock] = {}
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@contextlib.contextmanager
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def named_lock(name: str) -> c.Iterator[bool]:
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"""
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Context manager that provides named locks using threading.Lock instances.
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Once named lock instances are created they are not deleted.
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Returns True if this is the first instance of the named lock, otherwise False.
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"""
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with __named_lock:
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if lock_instance := __named_locks.get(name):
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first = False
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else:
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first = True
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lock_instance = __named_locks[name] = threading.Lock()
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with lock_instance:
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yield first
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