57 lines
1.7 KiB
Python
57 lines
1.7 KiB
Python
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import asyncio
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import functools
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import typing
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from typing import Any, AsyncGenerator, Iterator
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try:
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import contextvars # Python 3.7+ only.
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except ImportError: # pragma: no cover
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contextvars = None # type: ignore
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T = typing.TypeVar("T")
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async def run_until_first_complete(*args: typing.Tuple[typing.Callable, dict]) -> None:
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tasks = [handler(**kwargs) for handler, kwargs in args]
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(done, pending) = await asyncio.wait(tasks, return_when=asyncio.FIRST_COMPLETED)
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[task.cancel() for task in pending]
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[task.result() for task in done]
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async def run_in_threadpool(
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func: typing.Callable[..., T], *args: typing.Any, **kwargs: typing.Any
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) -> T:
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loop = asyncio.get_event_loop()
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if contextvars is not None: # pragma: no cover
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# Ensure we run in the same context
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child = functools.partial(func, *args, **kwargs)
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context = contextvars.copy_context()
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func = context.run
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args = (child,)
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elif kwargs: # pragma: no cover
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# loop.run_in_executor doesn't accept 'kwargs', so bind them in here
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func = functools.partial(func, **kwargs)
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return await loop.run_in_executor(None, func, *args)
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class _StopIteration(Exception):
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pass
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def _next(iterator: Iterator) -> Any:
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# We can't raise `StopIteration` from within the threadpool iterator
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# and catch it outside that context, so we coerce them into a different
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# exception type.
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try:
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return next(iterator)
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except StopIteration:
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raise _StopIteration
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async def iterate_in_threadpool(iterator: Iterator) -> AsyncGenerator:
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while True:
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try:
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yield await run_in_threadpool(_next, iterator)
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except _StopIteration:
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break
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