forked from goodboy/tractor
309 lines
12 KiB
Python
309 lines
12 KiB
Python
"""
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``trio`` inspired apis and helpers
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"""
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from functools import partial
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import multiprocessing as mp
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from typing import Tuple, List, Dict, Optional, Any
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import typing
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import trio
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from async_generator import asynccontextmanager
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from ._state import current_actor
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from .log import get_logger, get_loglevel
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from ._actor import Actor
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from ._portal import Portal
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from . import _state
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from . import _spawn
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log = get_logger(__name__)
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_default_bind_addr: Tuple[str, int] = ('127.0.0.1', 0)
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class ActorNursery:
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"""Spawn scoped subprocess actors.
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"""
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def __init__(
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self,
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actor: Actor,
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ria_nursery: trio.Nursery,
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da_nursery: trio.Nursery,
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errors: Dict[Tuple[str, str], Exception],
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) -> None:
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# self.supervisor = supervisor # TODO
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self._actor: Actor = actor
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self._ria_nursery = ria_nursery
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self._da_nursery = da_nursery
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self._children: Dict[
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Tuple[str, str],
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Tuple[Actor, mp.Process, Optional[Portal]]
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] = {}
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# portals spawned with ``run_in_actor()`` are
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# cancelled when their "main" result arrives
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self._cancel_after_result_on_exit: set = set()
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self.cancelled: bool = False
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self._join_procs = trio.Event()
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self.errors = errors
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async def start_actor(
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self,
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name: str,
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*,
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bind_addr: Tuple[str, int] = _default_bind_addr,
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statespace: Optional[Dict[str, Any]] = None,
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rpc_module_paths: List[str] = None,
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loglevel: str = None, # set log level per subactor
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nursery: trio.Nursery = None,
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) -> Portal:
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loglevel = loglevel or self._actor.loglevel or get_loglevel()
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# configure and pass runtime state
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_rtv = _state._runtime_vars.copy()
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_rtv['_is_root'] = False
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subactor = Actor(
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name,
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# modules allowed to invoked funcs from
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rpc_module_paths=rpc_module_paths or [],
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statespace=statespace, # global proc state vars
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loglevel=loglevel,
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arbiter_addr=current_actor()._arb_addr,
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)
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parent_addr = self._actor.accept_addr
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assert parent_addr
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# start a task to spawn a process
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# blocks until process has been started and a portal setup
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nursery = nursery or self._da_nursery
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# XXX: the type ignore is actually due to a `mypy` bug
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return await nursery.start( # type: ignore
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partial(
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_spawn.new_proc,
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name,
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self,
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subactor,
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self.errors,
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bind_addr,
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parent_addr,
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_rtv, # run time vars
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)
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)
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async def run_in_actor(
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self,
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name: str,
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fn: typing.Callable,
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*,
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bind_addr: Tuple[str, int] = _default_bind_addr,
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rpc_module_paths: Optional[List[str]] = None,
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statespace: Dict[str, Any] = None,
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loglevel: str = None, # set log level per subactor
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**kwargs, # explicit args to ``fn``
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) -> Portal:
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"""Spawn a new actor, run a lone task, then terminate the actor and
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return its result.
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Actors spawned using this method are kept alive at nursery teardown
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until the task spawned by executing ``fn`` completes at which point
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the actor is terminated.
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"""
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mod_path = fn.__module__
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portal = await self.start_actor(
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name,
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rpc_module_paths=[mod_path] + (rpc_module_paths or []),
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bind_addr=bind_addr,
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statespace=statespace,
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loglevel=loglevel,
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# use the run_in_actor nursery
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nursery=self._ria_nursery,
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)
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# this marks the actor to be cancelled after its portal result
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# is retreived, see logic in `open_nursery()` below.
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self._cancel_after_result_on_exit.add(portal)
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await portal._submit_for_result(
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mod_path,
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fn.__name__,
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**kwargs
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)
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return portal
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async def cancel(self, hard_kill: bool = False) -> None:
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"""Cancel this nursery by instructing each subactor to cancel
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itself and wait for all subactors to terminate.
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If ``hard_killl`` is set to ``True`` then kill the processes
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directly without any far end graceful ``trio`` cancellation.
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"""
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self.cancelled = True
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log.warning(f"Cancelling nursery in {self._actor.uid}")
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with trio.move_on_after(3) as cs:
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async with trio.open_nursery() as nursery:
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for subactor, proc, portal in self._children.values():
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if hard_kill:
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proc.terminate()
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else:
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if portal is None: # actor hasn't fully spawned yet
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event = self._actor._peer_connected[subactor.uid]
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log.warning(
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f"{subactor.uid} wasn't finished spawning?")
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await event.wait()
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# channel/portal should now be up
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_, _, portal = self._children[subactor.uid]
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# XXX should be impossible to get here
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# unless method was called from within
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# shielded cancel scope.
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if portal is None:
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# cancelled while waiting on the event
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# to arrive
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chan = self._actor._peers[subactor.uid][-1]
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if chan:
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portal = Portal(chan)
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else: # there's no other choice left
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proc.terminate()
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# spawn cancel tasks for each sub-actor
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assert portal
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nursery.start_soon(portal.cancel_actor)
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# if we cancelled the cancel (we hung cancelling remote actors)
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# then hard kill all sub-processes
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if cs.cancelled_caught:
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log.error(
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f"Failed to cancel {self}\nHard killing process tree!")
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for subactor, proc, portal in self._children.values():
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log.warning(f"Hard killing process {proc}")
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proc.terminate()
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# mark ourselves as having (tried to have) cancelled all subactors
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self._join_procs.set()
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@asynccontextmanager
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async def open_nursery() -> typing.AsyncGenerator[ActorNursery, None]:
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"""Create and yield a new ``ActorNursery`` to be used for spawning
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structured concurrent subactors.
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When an actor is spawned a new trio task is started which
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invokes one of the process spawning backends to create and start
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a new subprocess. These tasks are started by one of two nurseries
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detailed below. The reason for spawning processes from within
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a new task is because ``trio_run_in_process`` itself creates a new
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internal nursery and the same task that opens a nursery **must**
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close it. It turns out this approach is probably more correct
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anyway since it is more clear from the following nested nurseries
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which cancellation scopes correspond to each spawned subactor set.
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"""
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actor = current_actor()
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if not actor:
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raise RuntimeError("No actor instance has been defined yet?")
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# the collection of errors retreived from spawned sub-actors
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errors: Dict[Tuple[str, str], Exception] = {}
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# This is the outermost level "deamon actor" nursery. It is awaited
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# **after** the below inner "run in actor nursery". This allows for
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# handling errors that are generated by the inner nursery in
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# a supervisor strategy **before** blocking indefinitely to wait for
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# actors spawned in "daemon mode" (aka started using
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# ``ActorNursery.start_actor()``).
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async with trio.open_nursery() as da_nursery:
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try:
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# This is the inner level "run in actor" nursery. It is
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# awaited first since actors spawned in this way (using
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# ``ActorNusery.run_in_actor()``) are expected to only
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# return a single result and then complete (i.e. be canclled
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# gracefully). Errors collected from these actors are
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# immediately raised for handling by a supervisor strategy.
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# As such if the strategy propagates any error(s) upwards
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# the above "daemon actor" nursery will be notified.
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async with trio.open_nursery() as ria_nursery:
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anursery = ActorNursery(
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actor, ria_nursery, da_nursery, errors
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)
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try:
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# spawning of actors happens in the caller's scope
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# after we yield upwards
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yield anursery
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log.debug(
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f"Waiting on subactors {anursery._children} "
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"to complete"
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)
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except BaseException as err:
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# if the caller's scope errored then we activate our
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# one-cancels-all supervisor strategy (don't
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# worry more are coming).
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anursery._join_procs.set()
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try:
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# XXX: hypothetically an error could be raised and then
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# a cancel signal shows up slightly after in which case
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# the `else:` block here might not complete?
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# For now, shield both.
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with trio.CancelScope(shield=True):
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etype = type(err)
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if etype in (trio.Cancelled, KeyboardInterrupt):
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log.warning(
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f"Nursery for {current_actor().uid} was "
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f"cancelled with {etype}")
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else:
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log.exception(
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f"Nursery for {current_actor().uid} "
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f"errored with {err}, ")
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# cancel all subactors
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await anursery.cancel()
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except trio.MultiError as merr:
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# If we receive additional errors while waiting on
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# remaining subactors that were cancelled,
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# aggregate those errors with the original error
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# that triggered this teardown.
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if err not in merr.exceptions:
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raise trio.MultiError(merr.exceptions + [err])
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else:
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raise
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# Last bit before first nursery block ends in the case
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# where we didn't error in the caller's scope
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log.debug("Waiting on all subactors to complete")
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anursery._join_procs.set()
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# ria_nursery scope end
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# XXX: do we need a `trio.Cancelled` catch here as well?
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except (Exception, trio.MultiError, trio.Cancelled) as err:
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# If actor-local error was raised while waiting on
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# ".run_in_actor()" actors then we also want to cancel all
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# remaining sub-actors (due to our lone strategy:
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# one-cancels-all).
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log.warning(f"Nursery cancelling due to {err}")
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if anursery._children:
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with trio.CancelScope(shield=True):
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await anursery.cancel()
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raise
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finally:
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# No errors were raised while awaiting ".run_in_actor()"
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# actors but those actors may have returned remote errors as
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# results (meaning they errored remotely and have relayed
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# those errors back to this parent actor). The errors are
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# collected in ``errors`` so cancel all actors, summarize
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# all errors and re-raise.
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if errors:
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if anursery._children:
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with trio.CancelScope(shield=True):
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await anursery.cancel()
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# use `MultiError` as needed
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if len(errors) > 1:
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raise trio.MultiError(tuple(errors.values()))
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else:
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raise list(errors.values())[0]
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# ria_nursery scope end
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log.debug("Nursery teardown complete")
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