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tractor/tractor/_debug.py

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# tractor: structured concurrent "actors".
# Copyright 2018-eternity Tyler Goodlet.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
"""
Multi-core debugging for da peeps!
"""
from __future__ import annotations
import bdb
import sys
import signal
from functools import partial
from contextlib import asynccontextmanager as acm
from typing import (
Optional,
Callable,
AsyncIterator,
AsyncGenerator,
)
from types import FrameType
import tractor
import trio
from trio_typing import TaskStatus
from .log import get_logger
from ._discovery import get_root
from ._state import is_root_process, debug_mode
from ._exceptions import is_multi_cancelled
from ._ipc import Channel
try:
# wtf: only exported when installed in dev mode?
import pdbpp
except ImportError:
# pdbpp is installed in regular mode...it monkey patches stuff
import pdb
xpm = getattr(pdb, 'xpm', None)
assert xpm, "pdbpp is not installed?" # type: ignore
pdbpp = pdb
log = get_logger(__name__)
__all__ = ['breakpoint', 'post_mortem']
class Lock:
'''
Actor global debug lock state.
Mostly to avoid a lot of ``global`` declarations for now XD.
'''
# placeholder for function to set a ``trio.Event`` on debugger exit
# pdb_release_hook: Optional[Callable] = None
# actor-wide variable pointing to current task name using debugger
local_task_in_debug: Optional[str] = None
# actor tree-wide actor uid that supposedly has the tty lock
global_actor_in_debug: Optional[tuple[str, str]] = None
local_pdb_complete: Optional[trio.Event] = None
no_remote_has_tty: Optional[trio.Event] = None
# lock in root actor preventing multi-access to local tty
_debug_lock: trio.StrictFIFOLock = trio.StrictFIFOLock()
# XXX: set by the current task waiting on the root tty lock
# and must be cancelled if this actor is cancelled via message
# otherwise deadlocks with the parent actor may ensure
_debugger_request_cs: Optional[trio.CancelScope] = None
_orig_sigint_handler: Optional[Callable] = None
@classmethod
def shield_sigint(cls):
cls._orig_sigint_handler = signal.signal(
signal.SIGINT,
shield_sigint,
)
@classmethod
def unshield_sigint(cls):
if cls._orig_sigint_handler is not None:
# restore original sigint handler
signal.signal(
signal.SIGINT,
cls._orig_sigint_handler
)
cls._orig_sigint_handler = None
@classmethod
def release(cls):
try:
cls._debug_lock.release()
except RuntimeError:
# uhhh makes no sense but been seeing the non-owner
# release error even though this is definitely the task
# that locked?
owner = cls._debug_lock.statistics().owner
if owner:
raise
# actor-local state, irrelevant for non-root.
cls.global_actor_in_debug = None
cls.local_task_in_debug = None
try:
# sometimes the ``trio`` might already be terminated in
# which case this call will raise.
if cls.local_pdb_complete is not None:
cls.local_pdb_complete.set()
finally:
# restore original sigint handler
cls.unshield_sigint()
class TractorConfig(pdbpp.DefaultConfig):
'''
Custom ``pdbpp`` goodness.
'''
# use_pygments = True
# sticky_by_default = True
enable_hidden_frames = False
class MultiActorPdb(pdbpp.Pdb):
'''
Add teardown hooks to the regular ``pdbpp.Pdb``.
'''
# override the pdbpp config with our coolio one
DefaultConfig = TractorConfig
# def preloop(self):
# print('IN PRELOOP')
# super().preloop()
# TODO: figure out how to disallow recursive .set_trace() entry
# since that'll cause deadlock for us.
def set_continue(self):
try:
super().set_continue()
finally:
Lock.release()
def set_quit(self):
try:
super().set_quit()
finally:
Lock.release()
@acm
async def _acquire_debug_lock_from_root_task(
uid: tuple[str, str]
) -> AsyncIterator[trio.StrictFIFOLock]:
'''
Acquire a root-actor local FIFO lock which tracks mutex access of
the process tree's global debugger breakpoint.
This lock avoids tty clobbering (by preventing multiple processes
reading from stdstreams) and ensures multi-actor, sequential access
to the ``pdb`` repl.
'''
task_name = trio.lowlevel.current_task().name
log.runtime(
f"Attempting to acquire TTY lock, remote task: {task_name}:{uid}"
)
we_acquired = False
try:
log.runtime(
f"entering lock checkpoint, remote task: {task_name}:{uid}"
)
we_acquired = True
await Lock._debug_lock.acquire()
if Lock.no_remote_has_tty is None:
# mark the tty lock as being in use so that the runtime
# can try to avoid clobbering any connection from a child
# that's currently relying on it.
Lock.no_remote_has_tty = trio.Event()
Lock.global_actor_in_debug = uid
log.runtime(f"TTY lock acquired, remote task: {task_name}:{uid}")
# NOTE: critical section: this yield is unshielded!
# IF we received a cancel during the shielded lock entry of some
# next-in-queue requesting task, then the resumption here will
# result in that ``trio.Cancelled`` being raised to our caller
# (likely from ``lock_tty_for_child()`` below)! In
# this case the ``finally:`` below should trigger and the
# surrounding caller side context should cancel normally
# relaying back to the caller.
yield Lock._debug_lock
finally:
if (
we_acquired
and Lock._debug_lock.locked()
):
Lock._debug_lock.release()
# IFF there are no more requesting tasks queued up fire, the
# "tty-unlocked" event thereby alerting any monitors of the lock that
# we are now back in the "tty unlocked" state. This is basically
# and edge triggered signal around an empty queue of sub-actor
# tasks that may have tried to acquire the lock.
stats = Lock._debug_lock.statistics()
if (
not stats.owner
):
log.runtime(f"No more tasks waiting on tty lock! says {uid}")
if Lock.no_remote_has_tty is not None:
Lock.no_remote_has_tty.set()
Lock.no_remote_has_tty = None
Lock.global_actor_in_debug = None
log.runtime(
f"TTY lock released, remote task: {task_name}:{uid}"
)
@tractor.context
async def lock_tty_for_child(
ctx: tractor.Context,
subactor_uid: tuple[str, str]
) -> str:
'''
Lock the TTY in the root process of an actor tree in a new
inter-actor-context-task such that the ``pdbpp`` debugger console
can be mutex-allocated to the calling sub-actor for REPL control
without interference by other processes / threads.
NOTE: this task must be invoked in the root process of the actor
tree. It is meant to be invoked as an rpc-task and should be
highly reliable at releasing the mutex complete!
'''
task_name = trio.lowlevel.current_task().name
# TODO: when we get to true remote debugging
# this will deliver stdin data?
log.debug(
"Attempting to acquire TTY lock\n"
f"remote task: {task_name}:{subactor_uid}"
)
log.debug(f"Actor {subactor_uid} is WAITING on stdin hijack lock")
Lock.shield_sigint()
try:
with (
trio.CancelScope(shield=True),
):
async with _acquire_debug_lock_from_root_task(subactor_uid):
# indicate to child that we've locked stdio
await ctx.started('Locked')
log.debug(
f"Actor {subactor_uid} acquired stdin hijack lock"
)
# wait for unlock pdb by child
async with ctx.open_stream() as stream:
assert await stream.receive() == 'pdb_unlock'
return "pdb_unlock_complete"
finally:
Lock.unshield_sigint()
async def wait_for_parent_stdin_hijack(
actor_uid: tuple[str, str],
task_status: TaskStatus[trio.CancelScope] = trio.TASK_STATUS_IGNORED
):
'''
Connect to the root actor via a ``Context`` and invoke a task which
locks a root-local TTY lock: ``lock_tty_for_child()``; this func
should be called in a new task from a child actor **and never the
root*.
This function is used by any sub-actor to acquire mutex access to
the ``pdb`` REPL and thus the root's TTY for interactive debugging
(see below inside ``_breakpoint()``). It can be used to ensure that
an intermediate nursery-owning actor does not clobber its children
if they are in debug (see below inside
``maybe_wait_for_debugger()``).
'''
with trio.CancelScope(shield=True) as cs:
Lock._debugger_request_cs = cs
try:
async with get_root() as portal:
# this syncs to child's ``Context.started()`` call.
async with portal.open_context(
tractor._debug.lock_tty_for_child,
subactor_uid=actor_uid,
) as (ctx, val):
log.pdb('locked context')
assert val == 'Locked'
async with ctx.open_stream() as stream:
# unblock local caller
try:
assert Lock.local_pdb_complete
task_status.started(cs)
await Lock.local_pdb_complete.wait()
finally:
# TODO: shielding currently can cause hangs...
# with trio.CancelScope(shield=True):
await stream.send('pdb_unlock')
# sync with callee termination
assert await ctx.result() == "pdb_unlock_complete"
log.pdb('unlocked context')
except tractor.ContextCancelled:
log.warning('Root actor cancelled debug lock')
finally:
log.pdb(f"Exiting debugger for actor {actor_uid}")
Lock.local_task_in_debug = None
log.pdb(f"Child {actor_uid} released parent stdio lock")
def mk_mpdb() -> tuple[MultiActorPdb, Callable]:
pdb = MultiActorPdb()
# signal.signal = pdbpp.hideframe(signal.signal)
Lock.shield_sigint()
# XXX: These are the important flags mentioned in
# https://github.com/python-trio/trio/issues/1155
# which resolve the traceback spews to console.
pdb.allow_kbdint = True
pdb.nosigint = True
return pdb, Lock.unshield_sigint
async def _breakpoint(
debug_func,
# TODO:
# shield: bool = False
) -> None:
'''
Breakpoint entry for engaging debugger instance sync-interaction,
from async code, executing in actor runtime (task).
'''
__tracebackhide__ = True
pdb, undo_sigint = mk_mpdb()
actor = tractor.current_actor()
task_name = trio.lowlevel.current_task().name
# TODO: is it possible to debug a trio.Cancelled except block?
# right now it seems like we can kinda do with by shielding
# around ``tractor.breakpoint()`` but not if we move the shielded
# scope here???
# with trio.CancelScope(shield=shield):
# await trio.lowlevel.checkpoint()
if not Lock.local_pdb_complete or Lock.local_pdb_complete.is_set():
Lock.local_pdb_complete = trio.Event()
# TODO: need a more robust check for the "root" actor
if (
not is_root_process()
and actor._parent_chan # a connected child
):
if Lock.local_task_in_debug:
# Recurrence entry case: this task already has the lock and
# is likely recurrently entering a breakpoint
if Lock.local_task_in_debug == task_name:
# noop on recurrent entry case
return
# if **this** actor is already in debug mode block here
# waiting for the control to be released - this allows
# support for recursive entries to `tractor.breakpoint()`
log.warning(f"{actor.uid} already has a debug lock, waiting...")
await Lock.local_pdb_complete.wait()
await trio.sleep(0.1)
# mark local actor as "in debug mode" to avoid recurrent
# entries/requests to the root process
Lock.local_task_in_debug = task_name
# this **must** be awaited by the caller and is done using the
# root nursery so that the debugger can continue to run without
# being restricted by the scope of a new task nursery.
# NOTE: if we want to debug a trio.Cancelled triggered exception
# we have to figure out how to avoid having the service nursery
# cancel on this task start? I *think* this works below?
# actor._service_n.cancel_scope.shield = shield
try:
with trio.CancelScope(shield=True):
await actor._service_n.start(
wait_for_parent_stdin_hijack,
actor.uid,
)
except RuntimeError:
Lock.release()
raise
elif is_root_process():
# we also wait in the root-parent for any child that
# may have the tty locked prior
# TODO: wait, what about multiple root tasks acquiring it though?
if Lock.global_actor_in_debug == actor.uid:
# re-entrant root process already has it: noop.
return
# XXX: since we need to enter pdb synchronously below,
# we have to release the lock manually from pdb completion
# callbacks. Can't think of a nicer way then this atm.
if Lock._debug_lock.locked():
log.warning(
'Root actor attempting to shield-acquire active tty lock'
f' owned by {Lock.global_actor_in_debug}')
# must shield here to avoid hitting a ``Cancelled`` and
# a child getting stuck bc we clobbered the tty
with trio.CancelScope(shield=True):
await Lock._debug_lock.acquire()
else:
# may be cancelled
await Lock._debug_lock.acquire()
Lock.global_actor_in_debug = actor.uid
Lock.local_task_in_debug = task_name
try:
# block here one (at the appropriate frame *up*) where
# ``breakpoint()`` was awaited and begin handling stdio.
log.debug("Entering the synchronous world of pdb")
debug_func(actor, pdb)
except bdb.BdbQuit:
Lock.release()
raise
# XXX: apparently we can't do this without showing this frame
# in the backtrace on first entry to the REPL? Seems like an odd
# behaviour that should have been fixed by now. This is also why
# we scrapped all the @cm approaches that were tried previously.
# finally:
# __tracebackhide__ = True
# # frame = sys._getframe()
# # last_f = frame.f_back
# # last_f.f_globals['__tracebackhide__'] = True
# # signal.signal = pdbpp.hideframe(signal.signal)
# signal.signal(
# signal.SIGINT,
# orig_handler
# )
def shield_sigint(
signum: int,
frame: 'frame', # type: ignore # noqa
pdb_obj: Optional[MultiActorPdb] = None,
*args,
) -> None:
'''
Specialized debugger compatible SIGINT handler.
In childred we always ignore to avoid deadlocks since cancellation
should always be managed by the parent supervising actor. The root
is always cancelled on ctrl-c.
'''
__tracebackhide__ = True
uid_in_debug = Lock.global_actor_in_debug
actor = tractor.current_actor()
def do_cancel():
# If we haven't tried to cancel the runtime then do that instead
# of raising a KBI (which may non-gracefully destroy
# a ``trio.run()``).
if not actor._cancel_called:
actor.cancel_soon()
# If the runtime is already cancelled it likely means the user
# hit ctrl-c again because teardown didn't full take place in
# which case we do the "hard" raising of a local KBI.
else:
raise KeyboardInterrupt
any_connected = False
if uid_in_debug is not None:
# try to see if the supposed (sub)actor in debug still
# has an active connection to *this* actor, and if not
# it's likely they aren't using the TTY lock / debugger
# and we should propagate SIGINT normally.
chans = actor._peers.get(tuple(uid_in_debug))
if chans:
any_connected = any(chan.connected() for chan in chans)
if not any_connected:
log.warning(
'A global actor reported to be in debug '
'but no connection exists for this child:\n'
f'{uid_in_debug}\n'
'Allowing SIGINT propagation..'
)
return do_cancel()
# root actor branch that reports whether or not a child
# has locked debugger.
if (
is_root_process()
and uid_in_debug is not None
# XXX: only if there is an existing connection to the
# (sub-)actor in debug do we ignore SIGINT in this
# parent! Otherwise we may hang waiting for an actor
# which has already terminated to unlock.
and any_connected
):
name = uid_in_debug[0]
if name != 'root':
log.pdb(
f"Ignoring SIGINT while child in debug mode: `{uid_in_debug}`"
)
else:
log.pdb(
"Ignoring SIGINT while in debug mode"
)
# child actor that has locked the debugger
elif not is_root_process():
chan: Channel = actor._parent_chan
if not chan or not chan.connected():
log.warning(
'A global actor reported to be in debug '
'but no connection exists for its parent:\n'
f'{uid_in_debug}\n'
'Allowing SIGINT propagation..'
)
return do_cancel()
task = Lock.local_task_in_debug
if task:
log.pdb(
f"Ignoring SIGINT while task in debug mode: `{task}`"
)
# TODO: how to handle the case of an intermediary-child actor
# that **is not** marked in debug mode? See oustanding issue:
# https://github.com/goodboy/tractor/issues/320
# elif debug_mode():
else:
log.pdb(
"Ignoring SIGINT since debug mode is enabled"
)
# NOTE: currently (at least on ``fancycompleter`` 0.9.2)
# it lookks to be that the last command that was run (eg. ll)
# will be repeated by default.
# TODO: maybe redraw/print last REPL output to console
if (
pdb_obj
and sys.version_info <= (3, 10)
):
# TODO: make this work like sticky mode where if there is output
# detected as written to the tty we redraw this part underneath
# and erase the past draw of this same bit above?
# pdb_obj.sticky = True
# pdb_obj._print_if_sticky()
# also see these links for an approach from ``ptk``:
# https://github.com/goodboy/tractor/issues/130#issuecomment-663752040
# https://github.com/prompt-toolkit/python-prompt-toolkit/blob/c2c6af8a0308f9e5d7c0e28cb8a02963fe0ce07a/prompt_toolkit/patch_stdout.py
# XXX: lol, see ``pdbpp`` issue:
# https://github.com/pdbpp/pdbpp/issues/496
# TODO: pretty sure this is what we should expect to have to run
# in total but for now we're just going to wait until `pdbpp`
# figures out it's own stuff on 3.10 (and maybe we'll help).
# pdb_obj.do_longlist(None)
# XXX: we were doing this but it shouldn't be required..
print(pdb_obj.prompt, end='', flush=True)
def _set_trace(
actor: Optional[tractor.Actor] = None,
pdb: Optional[MultiActorPdb] = None,
):
__tracebackhide__ = True
actor = actor or tractor.current_actor()
# start 2 levels up in user code
frame: Optional[FrameType] = sys._getframe()
if frame:
frame = frame.f_back # type: ignore
if frame and pdb and actor is not None:
log.pdb(f"\nAttaching pdb to actor: {actor.uid}\n")
# no f!#$&* idea, but when we're in async land
# we need 2x frames up?
frame = frame.f_back
else:
pdb, undo_sigint = mk_mpdb()
# we entered the global ``breakpoint()`` built-in from sync code?
Lock.local_task_in_debug = 'sync'
pdb.set_trace(frame=frame)
breakpoint = partial(
_breakpoint,
_set_trace,
)
def _post_mortem(
actor: tractor.Actor,
pdb: MultiActorPdb,
) -> None:
'''
Enter the ``pdbpp`` port mortem entrypoint using our custom
debugger instance.
'''
log.pdb(f"\nAttaching to pdb in crashed actor: {actor.uid}\n")
# TODO: you need ``pdbpp`` master (at least this commit
# https://github.com/pdbpp/pdbpp/commit/b757794857f98d53e3ebbe70879663d7d843a6c2)
# to fix this and avoid the hang it causes. See issue:
# https://github.com/pdbpp/pdbpp/issues/480
# TODO: help with a 3.10+ major release if/when it arrives.
pdbpp.xpm(Pdb=lambda: pdb)
post_mortem = partial(
_breakpoint,
_post_mortem,
)
async def _maybe_enter_pm(err):
if (
debug_mode()
# NOTE: don't enter debug mode recursively after quitting pdb
# Iow, don't re-enter the repl if the `quit` command was issued
# by the user.
and not isinstance(err, bdb.BdbQuit)
# XXX: if the error is the likely result of runtime-wide
# cancellation, we don't want to enter the debugger since
# there's races between when the parent actor has killed all
# comms and when the child tries to contact said parent to
# acquire the tty lock.
# Really we just want to mostly avoid catching KBIs here so there
# might be a simpler check we can do?
and not is_multi_cancelled(err)
):
log.debug("Actor crashed, entering debug mode")
await post_mortem()
Lock.release()
return True
else:
return False
@acm
async def acquire_debug_lock(
subactor_uid: tuple[str, str],
) -> AsyncGenerator[None, tuple]:
'''
Grab root's debug lock on entry, release on exit.
This helper is for actor's who don't actually need
to acquired the debugger but want to wait until the
lock is free in the process-tree root.
'''
if not debug_mode():
yield None
return
async with trio.open_nursery() as n:
cs = await n.start(
wait_for_parent_stdin_hijack,
subactor_uid,
)
yield None
cs.cancel()
async def maybe_wait_for_debugger(
poll_steps: int = 2,
poll_delay: float = 0.1,
child_in_debug: bool = False,
) -> None:
if not debug_mode() and not child_in_debug:
return
if (
is_root_process()
):
# If we error in the root but the debugger is
# engaged we don't want to prematurely kill (and
# thus clobber access to) the local tty since it
# will make the pdb repl unusable.
# Instead try to wait for pdb to be released before
# tearing down.
sub_in_debug = None
for _ in range(poll_steps):
if Lock.global_actor_in_debug:
sub_in_debug = tuple(Lock.global_actor_in_debug)
log.debug('Root polling for debug')
with trio.CancelScope(shield=True):
await trio.sleep(poll_delay)
# TODO: could this make things more deterministic? wait
# to see if a sub-actor task will be scheduled and grab
# the tty lock on the next tick?
# XXX: doesn't seem to work
# await trio.testing.wait_all_tasks_blocked(cushion=0)
debug_complete = Lock.no_remote_has_tty
if (
(debug_complete and
not debug_complete.is_set())
):
log.debug(
'Root has errored but pdb is in use by '
f'child {sub_in_debug}\n'
'Waiting on tty lock to release..')
await debug_complete.wait()
await trio.sleep(poll_delay)
continue
else:
log.debug(
'Root acquired TTY LOCK'
)
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