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import enum |
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from types import TracebackType |
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from typing import final, Optional, Type |
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from . import events |
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from . import exceptions |
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from . import tasks |
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__all__ = ( |
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"Timeout", |
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"timeout", |
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"timeout_at", |
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) |
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class _State(enum.Enum): |
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CREATED = "created" |
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ENTERED = "active" |
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EXPIRING = "expiring" |
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EXPIRED = "expired" |
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EXITED = "finished" |
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@final |
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class Timeout: |
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"""Asynchronous context manager for cancelling overdue coroutines. |
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Use `timeout()` or `timeout_at()` rather than instantiating this class directly. |
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""" |
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def __init__(self, when: Optional[float]) -> None: |
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"""Schedule a timeout that will trigger at a given loop time. |
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- If `when` is `None`, the timeout will never trigger. |
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- If `when < loop.time()`, the timeout will trigger on the next |
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iteration of the event loop. |
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""" |
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self._state = _State.CREATED |
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self._timeout_handler: Optional[events.TimerHandle] = None |
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self._task: Optional[tasks.Task] = None |
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self._when = when |
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def when(self) -> Optional[float]: |
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"""Return the current deadline.""" |
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return self._when |
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def reschedule(self, when: Optional[float]) -> None: |
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"""Reschedule the timeout.""" |
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if self._state is not _State.ENTERED: |
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if self._state is _State.CREATED: |
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raise RuntimeError("Timeout has not been entered") |
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raise RuntimeError( |
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f"Cannot change state of {self._state.value} Timeout", |
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) |
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self._when = when |
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if self._timeout_handler is not None: |
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self._timeout_handler.cancel() |
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if when is None: |
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self._timeout_handler = None |
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else: |
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loop = events.get_running_loop() |
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if when <= loop.time(): |
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self._timeout_handler = loop.call_soon(self._on_timeout) |
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else: |
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self._timeout_handler = loop.call_at(when, self._on_timeout) |
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def expired(self) -> bool: |
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"""Is timeout expired during execution?""" |
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return self._state in (_State.EXPIRING, _State.EXPIRED) |
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def __repr__(self) -> str: |
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info = [''] |
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if self._state is _State.ENTERED: |
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when = round(self._when, 3) if self._when is not None else None |
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info.append(f"when={when}") |
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info_str = ' '.join(info) |
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return f"<Timeout [{self._state.value}]{info_str}>" |
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async def __aenter__(self) -> "Timeout": |
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if self._state is not _State.CREATED: |
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raise RuntimeError("Timeout has already been entered") |
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task = tasks.current_task() |
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if task is None: |
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raise RuntimeError("Timeout should be used inside a task") |
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self._state = _State.ENTERED |
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self._task = task |
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self._cancelling = self._task.cancelling() |
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self.reschedule(self._when) |
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return self |
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async def __aexit__( |
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self, |
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exc_type: Optional[Type[BaseException]], |
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exc_val: Optional[BaseException], |
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exc_tb: Optional[TracebackType], |
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) -> Optional[bool]: |
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assert self._state in (_State.ENTERED, _State.EXPIRING) |
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if self._timeout_handler is not None: |
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self._timeout_handler.cancel() |
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self._timeout_handler = None |
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if self._state is _State.EXPIRING: |
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self._state = _State.EXPIRED |
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if self._task.uncancel() <= self._cancelling and exc_type is exceptions.CancelledError: |
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raise TimeoutError from exc_val |
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elif self._state is _State.ENTERED: |
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self._state = _State.EXITED |
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return None |
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def _on_timeout(self) -> None: |
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assert self._state is _State.ENTERED |
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self._task.cancel() |
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self._state = _State.EXPIRING |
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self._timeout_handler = None |
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def timeout(delay: Optional[float]) -> Timeout: |
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"""Timeout async context manager. |
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Useful in cases when you want to apply timeout logic around block |
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of code or in cases when asyncio.wait_for is not suitable. For example: |
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>>> async with asyncio.timeout(10): # 10 seconds timeout |
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... await long_running_task() |
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delay - value in seconds or None to disable timeout logic |
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long_running_task() is interrupted by raising asyncio.CancelledError, |
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the top-most affected timeout() context manager converts CancelledError |
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into TimeoutError. |
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""" |
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loop = events.get_running_loop() |
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return Timeout(loop.time() + delay if delay is not None else None) |
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def timeout_at(when: Optional[float]) -> Timeout: |
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"""Schedule the timeout at absolute time. |
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Like timeout() but argument gives absolute time in the same clock system |
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as loop.time(). |
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Please note: it is not POSIX time but a time with |
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undefined starting base, e.g. the time of the system power on. |
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>>> async with asyncio.timeout_at(loop.time() + 10): |
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... await long_running_task() |
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when - a deadline when timeout occurs or None to disable timeout logic |
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long_running_task() is interrupted by raising asyncio.CancelledError, |
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the top-most affected timeout() context manager converts CancelledError |
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into TimeoutError. |
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""" |
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return Timeout(when) |
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