Scaffold `child_sigint` modes for forkserver
Add configuration surface for future child-side SIGINT
plumbing in `subint_forkserver_proc` without wiring up the
actual trio-native SIGINT bridge — lifting one entry-guard
clause will flip the `'trio'` branch live once the
underlying fork-prelude plumbing is implemented.
Deats,
- new `ChildSigintMode = Literal['ipc', 'trio']` type +
`_DEFAULT_CHILD_SIGINT = 'ipc'` module-level default.
Docstring block enumerates both:
- `'ipc'` (default, currently the only implemented mode):
no child-side SIGINT handler — `trio.run()` is on the
fork-inherited non-main thread where
`signal.set_wakeup_fd()` is main-thread-only, so
cancellation flows exclusively via the parent's
`Portal.cancel_actor()` IPC path. Known gap: orphan
children don't respond to SIGINT
(`test_orphaned_subactor_sigint_cleanup_DRAFT`)
- `'trio'` (scaffolded only): manual SIGINT → trio-cancel
bridge in the fork-child prelude so external Ctrl-C
reaches stuck grandchildren even w/ a dead parent
- `subint_forkserver_proc` pulls `child_sigint` out of
`proc_kwargs` (matches how `trio_proc` threads config to
`open_process`, keeps `start_actor(proc_kwargs=...)` as
the ergonomic entry point); validates membership + raises
`NotImplementedError` for `'trio'` at the backend-entry
guard
- `_child_target` grows a `match child_sigint:` arm that
slots in the future `'trio'` impl without restructuring
— today only the `'ipc'` case is reachable
- module docstring "Still-open work" list grows a bullet
pointing at this config + the xfail'd orphan-SIGINT test
No behavioral change on the default path — `'ipc'` is the
existing flow. Scaffolding only.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
parent
253e7cbd1c
commit
8a3f94ace0
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@ -66,6 +66,13 @@ Still-open work (tracked on tractor #379):
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- no cancellation / hard-kill stress coverage yet (counterpart
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to `tests/test_subint_cancellation.py` for the plain
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`subint` backend),
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- `child_sigint='trio'` mode (flag scaffolded below; default
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is `'ipc'`): install a manual SIGINT → trio-cancel bridge
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in the fork-child prelude so externally-delivered SIGINT
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reaches the child's trio loop even when the parent is
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dead (no IPC cancel path). See the xfail'd
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`test_orphaned_subactor_sigint_cleanup_DRAFT` for the
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target behavior.
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- child-side "subint-hosted root runtime" mode (the second
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half of the envisioned arch — currently the forked child
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runs plain `_trio_main` via `spawn_method='trio'`; the
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@ -115,6 +122,7 @@ from functools import partial
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from typing import (
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Any,
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Callable,
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Literal,
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TYPE_CHECKING,
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)
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@ -145,6 +153,31 @@ if TYPE_CHECKING:
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log = get_logger('tractor')
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# Configurable child-side SIGINT handling for forkserver-spawned
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# subactors. Threaded through `subint_forkserver_proc`'s
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# `proc_kwargs` under the `'child_sigint'` key.
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#
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# - `'ipc'` (default, currently the only implemented mode):
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# child has NO trio-level SIGINT handler — trio.run() is on
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# the fork-inherited non-main thread, `signal.set_wakeup_fd()`
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# is main-thread-only. Cancellation flows exclusively via
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# the parent's `Portal.cancel_actor()` IPC path. Safe +
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# deterministic for nursery-structured apps where the parent
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# is always the cancel authority. Known gap: orphan
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# (post-parent-SIGKILL) children don't respond to SIGINT
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# — see `test_orphaned_subactor_sigint_cleanup_DRAFT`.
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#
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# - `'trio'` (**not yet implemented**): install a manual
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# SIGINT → trio-cancel bridge in the child's fork prelude
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# (pre-`trio.run()`) so external Ctrl-C reaches stuck
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# grandchildren even with a dead parent. Adds signal-
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# handling surface the `'ipc'` default cleanly avoids; only
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# pay for it when externally-interruptible children actually
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# matter (e.g. CLI tool grandchildren).
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ChildSigintMode = Literal['ipc', 'trio']
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_DEFAULT_CHILD_SIGINT: ChildSigintMode = 'ipc'
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# Feature-gate: py3.14+ via the public `concurrent.interpreters`
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# wrapper. Matches the gate in `tractor.spawn._subint` —
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# see that module's docstring for why we require the public
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@ -537,13 +570,61 @@ async def subint_forkserver_proc(
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f'Current runtime: {sys.version}'
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)
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# Backend-scoped config pulled from `proc_kwargs`. Using
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# `proc_kwargs` (vs a first-class kwarg on this function)
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# matches how other backends expose per-spawn tuning
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# (`trio_proc` threads it to `trio.lowlevel.open_process`,
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# etc.) and keeps `ActorNursery.start_actor(proc_kwargs=...)`
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# as the single ergonomic entry point.
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child_sigint: ChildSigintMode = proc_kwargs.get(
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'child_sigint',
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_DEFAULT_CHILD_SIGINT,
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)
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if child_sigint not in ('ipc', 'trio'):
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raise ValueError(
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f'Invalid `child_sigint={child_sigint!r}` for '
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f'`subint_forkserver` backend.\n'
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f'Expected one of: {ChildSigintMode}.'
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)
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if child_sigint == 'trio':
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raise NotImplementedError(
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f"`child_sigint='trio'` mode — trio-native SIGINT "
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f"plumbing in the fork-child — is scaffolded but "
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f"not yet implemented. See the xfail'd "
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f"`test_orphaned_subactor_sigint_cleanup_DRAFT` "
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f"and the TODO in this module's docstring."
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)
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uid: tuple[str, str] = subactor.aid.uid
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loglevel: str | None = subactor.loglevel
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# Closure captured into the fork-child's memory image.
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# In the child this is the first post-fork Python code to
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# run, on what was the fork-worker thread in the parent.
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# `child_sigint` is captured here so the impl lands inside
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# this function once the `'trio'` mode is wired up —
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# nothing above this comment needs to change.
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def _child_target() -> int:
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# Dispatch on the captured SIGINT-mode closure var.
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# Today only `'ipc'` is reachable (the `'trio'` branch
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# is fenced off at the backend-entry guard above); the
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# match is in place so the future `'trio'` impl slots
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# in as a plain case arm without restructuring.
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match child_sigint:
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case 'ipc':
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pass # <- current behavior: no child-side
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# SIGINT plumbing; rely on parent
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# `Portal.cancel_actor()` IPC path.
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case 'trio':
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# Unreachable today (see entry-guard above);
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# this stub exists so that lifting the guard
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# is the only change required to enable
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# `'trio'` mode once the SIGINT wakeup-fd
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# bridge is implemented.
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raise NotImplementedError(
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"`child_sigint='trio'` fork-prelude "
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"plumbing not yet wired."
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)
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# Lazy import so the parent doesn't pay for it on
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# every spawn — it's module-level in `_child` but
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# cheap enough to re-resolve here.
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Loading…
Reference in New Issue