Viewing file:  timeouts.py (5.2 KB) -rw-r--r--
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import enum
from types import TracebackType
from typing import final, Optional, Type
from . import events
from . import exceptions
from . import tasks
__all__ = (
"Timeout",
"timeout",
"timeout_at",
)
class _State(enum.Enum):
CREATED = "created"
ENTERED = "active"
EXPIRING = "expiring"
EXPIRED = "expired"
EXITED = "finished"
@final
class Timeout:
"""Asynchronous context manager for cancelling overdue coroutines.
Use `timeout()` or `timeout_at()` rather than instantiating this class directly.
"""
def __init__(self, when: Optional[float]) -> None:
"""Schedule a timeout that will trigger at a given loop time.
- If `when` is `None`, the timeout will never trigger.
- If `when < loop.time()`, the timeout will trigger on the next
iteration of the event loop.
"""
self._state = _State.CREATED
self._timeout_handler: Optional[events.TimerHandle] = None
self._task: Optional[tasks.Task] = None
self._when = when
def when(self) -> Optional[float]:
"""Return the current deadline."""
return self._when
def reschedule(self, when: Optional[float]) -> None:
"""Reschedule the timeout."""
if self._state is not _State.ENTERED:
if self._state is _State.CREATED:
raise RuntimeError("Timeout has not been entered")
raise RuntimeError(
f"Cannot change state of {self._state.value} Timeout",
)
self._when = when
if self._timeout_handler is not None:
self._timeout_handler.cancel()
if when is None:
self._timeout_handler = None
else:
loop = events.get_running_loop()
if when <= loop.time():
self._timeout_handler = loop.call_soon(self._on_timeout)
else:
self._timeout_handler = loop.call_at(when, self._on_timeout)
def expired(self) -> bool:
"""Is timeout expired during execution?"""
return self._state in (_State.EXPIRING, _State.EXPIRED)
def __repr__(self) -> str:
info = ['']
if self._state is _State.ENTERED:
when = round(self._when, 3) if self._when is not None else None
info.append(f"when={when}")
info_str = ' '.join(info)
return f"<Timeout [{self._state.value}]{info_str}>"
async def __aenter__(self) -> "Timeout":
if self._state is not _State.CREATED:
raise RuntimeError("Timeout has already been entered")
task = tasks.current_task()
if task is None:
raise RuntimeError("Timeout should be used inside a task")
self._state = _State.ENTERED
self._task = task
self._cancelling = self._task.cancelling()
self.reschedule(self._when)
return self
async def __aexit__(
self,
exc_type: Optional[Type[BaseException]],
exc_val: Optional[BaseException],
exc_tb: Optional[TracebackType],
) -> Optional[bool]:
assert self._state in (_State.ENTERED, _State.EXPIRING)
if self._timeout_handler is not None:
self._timeout_handler.cancel()
self._timeout_handler = None
if self._state is _State.EXPIRING:
self._state = _State.EXPIRED
if self._task.uncancel() <= self._cancelling and exc_type is exceptions.CancelledError:
# Since there are no new cancel requests, we're
# handling this.
raise TimeoutError from exc_val
elif self._state is _State.ENTERED:
self._state = _State.EXITED
return None
def _on_timeout(self) -> None:
assert self._state is _State.ENTERED
self._task.cancel()
self._state = _State.EXPIRING
# drop the reference early
self._timeout_handler = None
def timeout(delay: Optional[float]) -> Timeout:
"""Timeout async context manager.
Useful in cases when you want to apply timeout logic around block
of code or in cases when asyncio.wait_for is not suitable. For example:
>>> async with asyncio.timeout(10): # 10 seconds timeout
... await long_running_task()
delay - value in seconds or None to disable timeout logic
long_running_task() is interrupted by raising asyncio.CancelledError,
the top-most affected timeout() context manager converts CancelledError
into TimeoutError.
"""
loop = events.get_running_loop()
return Timeout(loop.time() + delay if delay is not None else None)
def timeout_at(when: Optional[float]) -> Timeout:
"""Schedule the timeout at absolute time.
Like timeout() but argument gives absolute time in the same clock system
as loop.time().
Please note: it is not POSIX time but a time with
undefined starting base, e.g. the time of the system power on.
>>> async with asyncio.timeout_at(loop.time() + 10):
... await long_running_task()
when - a deadline when timeout occurs or None to disable timeout logic
long_running_task() is interrupted by raising asyncio.CancelledError,
the top-most affected timeout() context manager converts CancelledError
into TimeoutError.
"""
return Timeout(when)
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