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97 lines
3.2 KiB
Python
97 lines
3.2 KiB
Python
import ctypes
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import logging
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import sys
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import threading
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import time
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from types import TracebackType
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from typing import Callable, Optional, Tuple, Type, TypeVar
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# Based on https://code.activestate.com/recipes/483752/
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class TimeoutExpiredError(Exception):
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"""Exception raised when a function times out."""
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def __str__(self) -> str:
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return "Function call timed out."
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ResultT = TypeVar("ResultT")
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def timeout(timeout: float, func: Callable[[], ResultT]) -> ResultT:
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"""Call the function in a separate thread.
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Return its return value, or raise an exception,
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within approximately 'timeout' seconds.
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The function may receive a TimeoutExpiredError exception
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anywhere in its code, which could have arbitrary
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unsafe effects (resources not released, etc.).
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It might also fail to receive the exception and
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keep running in the background even though
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timeout() has returned.
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This may also fail to interrupt functions which are
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stuck in a long-running primitive interpreter
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operation."""
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class TimeoutThread(threading.Thread):
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def __init__(self) -> None:
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threading.Thread.__init__(self)
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self.result: Optional[ResultT] = None
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self.exc_info: Tuple[
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Optional[Type[BaseException]],
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Optional[BaseException],
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Optional[TracebackType],
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] = (None, None, None)
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# Don't block the whole program from exiting
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# if this is the only thread left.
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self.daemon = True
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def run(self) -> None:
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try:
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self.result = func()
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except BaseException:
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self.exc_info = sys.exc_info()
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def raise_async_timeout(self) -> None:
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# This function is called from another thread; we attempt
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# to raise a TimeoutExpiredError in _this_ thread.
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assert self.ident is not None
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ctypes.pythonapi.PyThreadState_SetAsyncExc(
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ctypes.c_ulong(self.ident),
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ctypes.py_object(TimeoutExpiredError),
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)
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thread = TimeoutThread()
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thread.start()
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thread.join(timeout)
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if thread.is_alive():
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# We need to retry, because an async exception received while
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# the thread is in a system call is simply ignored.
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for i in range(10):
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thread.raise_async_timeout()
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time.sleep(0.1)
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if not thread.is_alive():
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break
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if thread.exc_info[1] is not None:
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# Re-raise the exception we sent, if possible, so the
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# stacktrace originates in the slow code
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raise thread.exc_info[1].with_traceback(thread.exc_info[2])
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# If we don't have that for some reason (e.g. we failed to
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# kill it), just raise from here; the thread _may still be
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# running_ because it failed to see any of our exceptions, and
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# we just ignore it.
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if thread.is_alive():
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logging.warning("Failed to time out backend thread")
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raise TimeoutExpiredError
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if thread.exc_info[1] is not None:
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# Died with some other exception; re-raise it
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raise thread.exc_info[1].with_traceback(thread.exc_info[2])
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assert thread.result is not None
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return thread.result
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