forked from goodboy/tractor
95 lines
2.7 KiB
Python
95 lines
2.7 KiB
Python
# tractor: structured concurrent "actors".
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# Copyright 2018-eternity Tyler Goodlet.
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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'''
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Async context manager primitives with hard ``trio``-aware semantics
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'''
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from typing import AsyncContextManager, AsyncGenerator
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from typing import TypeVar, Sequence
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from contextlib import asynccontextmanager as acm
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import trio
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# A regular invariant generic type
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T = TypeVar("T")
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async def _enter_and_wait(
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mngr: AsyncContextManager[T],
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unwrapped: dict[int, T],
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all_entered: trio.Event,
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parent_exit: trio.Event,
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) -> None:
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'''
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Open the async context manager deliver it's value
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to this task's spawner and sleep until cancelled.
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'''
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async with mngr as value:
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unwrapped[id(mngr)] = value
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if all(unwrapped.values()):
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all_entered.set()
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await parent_exit.wait()
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@acm
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async def gather_contexts(
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mngrs: Sequence[AsyncContextManager[T]],
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) -> AsyncGenerator[tuple[T, ...], None]:
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'''
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Concurrently enter a sequence of async context managers, each in
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a separate ``trio`` task and deliver the unwrapped values in the
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same order once all managers have entered. On exit all contexts are
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subsequently and concurrently exited.
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This function is somewhat similar to common usage of
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``contextlib.AsyncExitStack.enter_async_context()`` (in a loop) in
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combo with ``asyncio.gather()`` except the managers are concurrently
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entered and exited cancellation just works.
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'''
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unwrapped = {}.fromkeys(id(mngr) for mngr in mngrs)
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all_entered = trio.Event()
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parent_exit = trio.Event()
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async with trio.open_nursery() as n:
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for mngr in mngrs:
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n.start_soon(
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_enter_and_wait,
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mngr,
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unwrapped,
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all_entered,
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parent_exit,
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)
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# deliver control once all managers have started up
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await all_entered.wait()
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yield tuple(unwrapped.values())
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# we don't need a try/finally since cancellation will be triggered
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# by the surrounding nursery on error.
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parent_exit.set()
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