forked from goodboy/tractor
Simplify to soft and hard reap sequences
This is actually surprisingly easy to grok having gone through a lot of pain understanding edge cases in the zombie lord dev branch. Basically we just need to make sure actors are managed in a 2 step reap sequence. In the "soft" reap phase we wait for the process to terminate on its own concurrently with (maybe) waiting for its portal's final result (if it's a `.run_in_actor()`). If this path is cancelled or errors, then we do a "hard" reap where we timeout and send a signal to the proc to terminate immediately. The only last remaining trick is to tie in the root-is-debugger-aware logic to yet again avoid tty clobbers.immediate_remote_cancels
Tyler Goodlet
parent
2df16c1557
commit
77ec29008d
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@ -8,7 +8,6 @@ from typing import Any, Dict, Optional
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import trio
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from trio_typing import TaskStatus
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from async_generator import asynccontextmanager
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try:
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from multiprocessing import semaphore_tracker # type: ignore
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@ -123,34 +122,32 @@ async def cancel_on_completion(
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portal: Portal,
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actor: Actor,
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errors: Dict[Tuple[str, str], Exception],
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task_status: TaskStatus[trio.CancelScope] = trio.TASK_STATUS_IGNORED,
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) -> None:
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"""Cancel actor gracefully once it's "main" portal's
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"""
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Cancel actor gracefully once it's "main" portal's
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result arrives.
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Should only be called for actors spawned with `run_in_actor()`.
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"""
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with trio.CancelScope() as cs:
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# if this call errors we store the exception for later
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# in ``errors`` which will be reraised inside
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# a MultiError and we still send out a cancel request
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result = await exhaust_portal(portal, actor)
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if isinstance(result, Exception):
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errors[actor.uid] = result
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log.warning(
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f"Cancelling {portal.channel.uid} after error {result}"
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)
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task_status.started(cs)
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else:
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log.runtime(
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f"Cancelling {portal.channel.uid} gracefully "
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f"after result {result}")
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# if this call errors we store the exception for later
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# in ``errors`` which will be reraised inside
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# a MultiError and we still send out a cancel request
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result = await exhaust_portal(portal, actor)
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if isinstance(result, Exception):
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errors[actor.uid] = result
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log.warning(
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f"Cancelling {portal.channel.uid} after error {result}"
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)
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else:
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log.runtime(
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f"Cancelling {portal.channel.uid} gracefully "
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f"after result {result}")
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# cancel the process now that we have a final result
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await portal.cancel_actor()
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# cancel the process now that we have a final result
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await portal.cancel_actor()
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async def do_hard_kill(
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@ -191,8 +188,6 @@ async def new_proc(
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spawn method as configured using ``try_set_start_method()``.
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"""
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cancel_scope = None
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# mark the new actor with the global spawn method
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subactor._spawn_method = _spawn_method
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@ -258,7 +253,8 @@ async def new_proc(
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async with trio.open_nursery() as nursery:
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if portal in actor_nursery._cancel_after_result_on_exit:
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cancel_scope = await nursery.start(
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# cancel_scope = await nursery.start(
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nursery.start_soon(
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cancel_on_completion,
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portal,
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subactor,
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@ -271,22 +267,22 @@ async def new_proc(
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# This is a "soft" (cancellable) join/reap.
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await proc.wait()
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finally:
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# cancel result waiter that may have been spawned in
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# tandem if not done already
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if cancel_scope:
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# cancel result waiter that may have been spawned in
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# tandem if not done already
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log.warning(
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"Cancelling existing result waiter task for "
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f"{subactor.uid}")
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cancel_scope.cancel()
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nursery.cancel_scope.cancel()
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log.runtime(f"Attempting to kill {proc}")
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finally:
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if proc.poll() is None:
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log.cancel(f"Attempting to hard kill {proc}")
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# The "hard" reap since no actor zombies are allowed!
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# XXX: do this **after** cancellation/tearfown to avoid
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# killing the process too early.
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with trio.CancelScope(shield=True):
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await do_hard_kill(proc)
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# The "hard" reap since no actor zombies are allowed!
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# XXX: do this **after** cancellation/tearfown to avoid
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# killing the process too early.
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with trio.CancelScope(shield=True):
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await do_hard_kill(proc)
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log.debug(f"Joined {proc}")
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# pop child entry to indicate we no longer managing this subactor
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@ -322,141 +318,124 @@ async def mp_new_proc(
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task_status: TaskStatus[Portal] = trio.TASK_STATUS_IGNORED
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) -> None:
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async with trio.open_nursery() as nursery:
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assert _ctx
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start_method = _ctx.get_start_method()
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if start_method == 'forkserver':
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# XXX do our hackery on the stdlib to avoid multiple
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# forkservers (one at each subproc layer).
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fs = forkserver._forkserver
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curr_actor = current_actor()
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if is_main_process() and not curr_actor._forkserver_info:
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# if we're the "main" process start the forkserver
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# only once and pass its ipc info to downstream
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# children
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# forkserver.set_forkserver_preload(enable_modules)
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forkserver.ensure_running()
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fs_info = (
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fs._forkserver_address,
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fs._forkserver_alive_fd,
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getattr(fs, '_forkserver_pid', None),
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getattr(
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resource_tracker._resource_tracker, '_pid', None),
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resource_tracker._resource_tracker._fd,
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)
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else:
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assert curr_actor._forkserver_info
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fs_info = (
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fs._forkserver_address,
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fs._forkserver_alive_fd,
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fs._forkserver_pid,
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resource_tracker._resource_tracker._pid,
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resource_tracker._resource_tracker._fd,
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) = curr_actor._forkserver_info
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assert _ctx
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start_method = _ctx.get_start_method()
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if start_method == 'forkserver':
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# XXX do our hackery on the stdlib to avoid multiple
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# forkservers (one at each subproc layer).
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fs = forkserver._forkserver
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curr_actor = current_actor()
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if is_main_process() and not curr_actor._forkserver_info:
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# if we're the "main" process start the forkserver
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# only once and pass its ipc info to downstream
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# children
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# forkserver.set_forkserver_preload(enable_modules)
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forkserver.ensure_running()
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fs_info = (
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fs._forkserver_address,
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fs._forkserver_alive_fd,
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getattr(fs, '_forkserver_pid', None),
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getattr(
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resource_tracker._resource_tracker, '_pid', None),
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resource_tracker._resource_tracker._fd,
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)
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else:
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fs_info = (None, None, None, None, None)
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assert curr_actor._forkserver_info
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fs_info = (
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fs._forkserver_address,
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fs._forkserver_alive_fd,
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fs._forkserver_pid,
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resource_tracker._resource_tracker._pid,
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resource_tracker._resource_tracker._fd,
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) = curr_actor._forkserver_info
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else:
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fs_info = (None, None, None, None, None)
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proc: mp.Process = _ctx.Process( # type: ignore
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target=_mp_main,
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args=(
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subactor,
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bind_addr,
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fs_info,
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start_method,
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parent_addr,
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),
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# daemon=True,
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name=name,
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)
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# `multiprocessing` only (since no async interface):
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# register the process before start in case we get a cancel
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# request before the actor has fully spawned - then we can wait
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# for it to fully come up before sending a cancel request
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actor_nursery._children[subactor.uid] = (subactor, proc, None)
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proc: mp.Process = _ctx.Process( # type: ignore
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target=_mp_main,
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args=(
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subactor,
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bind_addr,
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fs_info,
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start_method,
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parent_addr,
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),
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# daemon=True,
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name=name,
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)
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# `multiprocessing` only (since no async interface):
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# register the process before start in case we get a cancel
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# request before the actor has fully spawned - then we can wait
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# for it to fully come up before sending a cancel request
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actor_nursery._children[subactor.uid] = (subactor, proc, None)
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proc.start()
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if not proc.is_alive():
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raise ActorFailure("Couldn't start sub-actor?")
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proc.start()
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if not proc.is_alive():
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raise ActorFailure("Couldn't start sub-actor?")
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log.runtime(f"Started {proc}")
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log.runtime(f"Started {proc}")
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try:
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# wait for actor to spawn and connect back to us
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# channel should have handshake completed by the
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# local actor by the time we get a ref to it
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event, chan = await actor_nursery._actor.wait_for_peer(
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subactor.uid)
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portal = Portal(chan)
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actor_nursery._children[subactor.uid] = (subactor, proc, portal)
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try:
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# wait for actor to spawn and connect back to us
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# channel should have handshake completed by the
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# local actor by the time we get a ref to it
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event, chan = await actor_nursery._actor.wait_for_peer(
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subactor.uid)
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# except:
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# TODO: in the case we were cancelled before the sub-proc
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# registered itself back we must be sure to try and clean
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# any process we may have started.
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# unblock parent task
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task_status.started(portal)
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portal = Portal(chan)
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actor_nursery._children[subactor.uid] = (subactor, proc, portal)
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# wait for ``ActorNursery`` block to signal that
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# subprocesses can be waited upon.
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# This is required to ensure synchronization
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# with user code that may want to manually await results
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# from nursery spawned sub-actors. We don't want the
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# containing nurseries here to collect results or error
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# while user code is still doing it's thing. Only after the
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# nursery block closes do we allow subactor results to be
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# awaited and reported upwards to the supervisor.
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# unblock parent task
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task_status.started(portal)
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# wait for ``ActorNursery`` block to signal that
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# subprocesses can be waited upon.
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# This is required to ensure synchronization
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# with user code that may want to manually await results
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# from nursery spawned sub-actors. We don't want the
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# containing nurseries here to collect results or error
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# while user code is still doing it's thing. Only after the
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# nursery block closes do we allow subactor results to be
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# awaited and reported upwards to the supervisor.
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with trio.CancelScope(shield=True):
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await actor_nursery._join_procs.wait()
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finally:
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# XXX: in the case we were cancelled before the sub-proc
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# registered itself back we must be sure to try and clean
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# any process we may have started.
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reaping_cancelled: bool = False
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cancel_scope: Optional[trio.CancelScope] = None
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cancel_exc: Optional[trio.Cancelled] = None
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async with trio.open_nursery() as nursery:
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if portal in actor_nursery._cancel_after_result_on_exit:
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try:
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# async with trio.open_nursery() as n:
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# n.cancel_scope.shield = True
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cancel_scope = await nursery.start(
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cancel_on_completion,
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portal,
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subactor,
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errors
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)
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except trio.Cancelled as err:
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cancel_exc = err
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nursery.start_soon(
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cancel_on_completion,
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portal,
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subactor,
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errors
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)
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# if the reaping task was cancelled we may have hit
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# a race where the subproc disconnected before we
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# could send it a message to cancel (classic 2 generals)
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# in that case, wait shortly then kill the process.
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reaping_cancelled = True
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if proc.is_alive():
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with trio.move_on_after(0.1) as cs:
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cs.shield = True
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await proc_waiter(proc)
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if cs.cancelled_caught:
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proc.terminate()
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if not reaping_cancelled and proc.is_alive():
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await proc_waiter(proc)
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# TODO: timeout block here?
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proc.join()
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log.debug(f"Joined {proc}")
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# pop child entry to indicate we are no longer managing subactor
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subactor, proc, portal = actor_nursery._children.pop(subactor.uid)
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await proc_waiter(proc)
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# cancel result waiter that may have been spawned in
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# tandem if not done already
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if cancel_scope:
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log.warning(
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"Cancelling existing result waiter task for "
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f"{subactor.uid}")
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cancel_scope.cancel()
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log.warning(
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"Cancelling existing result waiter task for "
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f"{subactor.uid}")
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nursery.cancel_scope.cancel()
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elif reaping_cancelled: # let the cancellation bubble up
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assert cancel_exc
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raise cancel_exc
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finally:
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# hard reap sequence
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if proc.is_alive():
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log.cancel(f"Attempting to hard kill {proc}")
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with trio.move_on_after(0.1) as cs:
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cs.shield = True
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await proc_waiter(proc)
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if cs.cancelled_caught:
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proc.terminate()
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proc.join()
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log.debug(f"Joined {proc}")
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# pop child entry to indicate we are no longer managing subactor
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subactor, proc, portal = actor_nursery._children.pop(subactor.uid)
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