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365fe0b3d5
Fixes #2665. Regenerated by tabbott with `lint --fix` after a rebase and change in parameters. Note from tabbott: In a few cases, this converts technical debt in the form of unsorted imports into different technical debt in the form of our largest files having very long, ugly import sequences at the start. I expect this change will increase pressure for us to split those files, which isn't a bad thing. Signed-off-by: Anders Kaseorg <anders@zulip.com>
93 lines
3.5 KiB
Python
93 lines
3.5 KiB
Python
import ctypes
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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 Any, Callable, Optional, Tuple, Type, TypeVar
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# Based on https://code.activestate.com/recipes/483752/
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class TimeoutExpired(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], *args: Any, **kwargs: Any) -> 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 TimeoutExpired 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(*args, **kwargs)
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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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# Called from another thread.
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# Attempt to raise a TimeoutExpired in the thread represented by 'self'.
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assert self.ident is not None # Thread should be running; c_long expects int
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tid = ctypes.c_long(self.ident)
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result = ctypes.pythonapi.PyThreadState_SetAsyncExc(
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tid, ctypes.py_object(TimeoutExpired))
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if result > 1:
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# "if it returns a number greater than one, you're in trouble,
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# and you should call it again with exc=NULL to revert the effect"
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#
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# I was unable to find the actual source of this quote, but it
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# appears in the many projects across the Internet that have
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# copy-pasted this recipe.
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ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, None)
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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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# Gamely try to kill the thread, following the dodgy approach from
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# https://stackoverflow.com/a/325528/90777
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#
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# We need to retry, because an async exception received while the
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# 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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raise TimeoutExpired
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if thread.exc_info[1] is not None:
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# Raise the original stack trace so our error messages are more useful.
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# from https://stackoverflow.com/a/4785766/90777
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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 # assured if above did not reraise
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return thread.result
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