11890040966

Committed 18 Nov 2024 10:01AM UTC coverage: 92.023% (-0.3%) from 92.285%

Build # 11890040966

Build Type

Pull #820

github

Committed by

web-flow

Commit Message

Merge 872329a27 into 6224525ed

Pull Request Pull Request #820: Use ThreadSelectorEventLoop on Windows with ProactorEventLoop

Run Details

141 of 167 new or added lines in 2 files covered. (84.43%)

1 existing line in 1 file now uncovered.

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82.67

/src/anyio/_backends/_selector_thread.py

"""Ensure asyncio selector methods (add_reader, etc.) are available.
Running select in a thread and defining these methods on the running event loop.
Originally in tornado.platform.asyncio.
Redistributed under license Apache-2.0
"""

from __future__ import annotations

import asyncio
import errno
import functools
import select
import socket
import threading
import typing
from typing import (
    TYPE_CHECKING,
    Any,
    Callable,
    Union,
)
from weakref import WeakKeyDictionary

from ._asyncio import find_root_task

if TYPE_CHECKING:
    from _typeshed import HasFileno

    _FileDescriptorLike = HasFileno | int


# registry of asyncio loop : selector thread
_selectors: WeakKeyDictionary = WeakKeyDictionary()

# Collection of selector thread event loops to shut down on exit.
_selector_loops: set[SelectorThread] = set()


def _at_loop_close_callback(future: asyncio.Future) -> None:
    for loop in _selector_loops:
        with loop._select_cond:
            loop._closing_selector = True
            loop._select_cond.notify()
        try:
            loop._waker_w.send(b"a")
        except BlockingIOError:
            pass
        # If we don't join our (daemon) thread here, we may get a deadlock
        # during interpreter shutdown. I don't really understand why. This
        # deadlock happens every time in CI (both travis and appveyor) but
        # I've never been able to reproduce locally.
        assert loop._thread is not None
        loop._thread.join()
    _selector_loops.clear()


# SelectorThread from tornado 6.4.0
class SelectorThread:
    """Define ``add_reader`` methods to be called in a background select thread.

    Instances of this class start a second thread to run a selector.
    This thread is completely hidden from the user;
    all callbacks are run on the wrapped event loop's thread.

    Typically used via ``AddThreadSelectorEventLoop``,
    but can be attached to a running asyncio loop.
    """

    _closed = False

    def __init__(self, real_loop: asyncio.AbstractEventLoop) -> None:
        self._real_loop = real_loop

        self._select_cond = threading.Condition()
        self._select_args: (
            tuple[list[_FileDescriptorLike], list[_FileDescriptorLike]] | None
        ) = None
        self._closing_selector = False
        self._thread: threading.Thread | None = None

        self._readers: dict[_FileDescriptorLike, Callable] = {}
        self._writers: dict[_FileDescriptorLike, Callable] = {}

        # Writing to _waker_w will wake up the selector thread, which
        # watches for _waker_r to be readable.
        self._waker_r, self._waker_w = socket.socketpair()
        self._waker_r.setblocking(False)
        self._waker_w.setblocking(False)
        _selector_loops.add(self)
        self.add_reader(self._waker_r, self._consume_waker)
        self._thread_manager()

    def close(self) -> None:
        if self._closed:
            return
        with self._select_cond:
            self._closing_selector = True
            self._select_cond.notify()
        self._wake_selector()
        if self._thread is not None:
            self._thread.join()
        _selector_loops.discard(self)
        self.remove_reader(self._waker_r)
        self._waker_r.close()
        self._waker_w.close()
        self._closed = True

    def _thread_manager(self) -> None:
        # Create a thread to run the select system call. We manage this thread
        # manually so we can trigger a clean shutdown at loop teardown. Note
        # that due to the order of operations at shutdown, only daemon threads
        # can be shut down in this way (non-daemon threads would require the
        # introduction of a new hook: https://bugs.python.org/issue41962)
        self._thread = threading.Thread(
            name="AnyIO selector",
            daemon=True,
            target=self._run_select,
        )
        self._thread.start()
        self._start_select()

    def _wake_selector(self) -> None:
        if self._closed:
            return
        try:
            self._waker_w.send(b"a")
        except BlockingIOError:
            pass

    def _consume_waker(self) -> None:
        try:
            self._waker_r.recv(1024)
        except BlockingIOError:
            pass

    def _start_select(self) -> None:
        # Capture reader and writer sets here in the event loop
        # thread to avoid any problems with concurrent
        # modification while the select loop uses them.
        with self._select_cond:
            assert self._select_args is None
            self._select_args = (list(self._readers.keys()), list(self._writers.keys()))
            self._select_cond.notify()

    def _run_select(self) -> None:
        while True:
            with self._select_cond:
                while self._select_args is None and not self._closing_selector:
                    self._select_cond.wait()
                if self._closing_selector:
                    return
                assert self._select_args is not None
                to_read, to_write = self._select_args
                self._select_args = None

            # We use the simpler interface of the select module instead of
            # the more stateful interface in the selectors module because
            # this class is only intended for use on windows, where
            # select.select is the only option. The selector interface
            # does not have well-documented thread-safety semantics that
            # we can rely on so ensuring proper synchronization would be
            # tricky.
            try:
                # On windows, selecting on a socket for write will not
                # return the socket when there is an error (but selecting
                # for reads works). Also select for errors when selecting
                # for writes, and merge the results.
                #
                # This pattern is also used in
                # https://github.com/python/cpython/blob/v3.8.0/Lib/selectors.py#L312-L317
                rs, ws, xs = select.select(to_read, to_write, to_write)
                ws = ws + xs
            except OSError as e:
                # After remove_reader or remove_writer is called, the file
                # descriptor may subsequently be closed on the event loop
                # thread. It's possible that this select thread hasn't
                # gotten into the select system call by the time that
                # happens in which case (at least on macOS), select may
                # raise a "bad file descriptor" error. If we get that
                # error, check and see if we're also being woken up by
                # polling the waker alone. If we are, just return to the
                # event loop and we'll get the updated set of file
                # descriptors on the next iteration. Otherwise, raise the
                # original error.
                if e.errno == getattr(errno, "WSAENOTSOCK", errno.EBADF):
                    rs, _, _ = select.select([self._waker_r.fileno()], [], [], 0)
                    if rs:
                        ws = []
                    else:
                        raise
                else:
                    raise

            try:
                self._real_loop.call_soon_threadsafe(self._handle_select, rs, ws)
            except RuntimeError:
                # "Event loop is closed". Swallow the exception for
                # consistency with PollIOLoop (and logical consistency
                # with the fact that we can't guarantee that an
                # add_callback that completes without error will
                # eventually execute).
                pass
            except AttributeError:
                # ProactorEventLoop may raise this instead of RuntimeError
                # if call_soon_threadsafe races with a call to close().
                # Swallow it too for consistency.
                pass

    def _handle_select(
        self, rs: list[_FileDescriptorLike], ws: list[_FileDescriptorLike]
    ) -> None:
        for r in rs:
            self._handle_event(r, self._readers)
        for w in ws:
            self._handle_event(w, self._writers)
        self._start_select()

    def _handle_event(
        self,
        fd: _FileDescriptorLike,
        cb_map: dict[_FileDescriptorLike, Callable],
    ) -> None:
        try:
            callback = cb_map[fd]
        except KeyError:
            return
        callback()

    def add_reader(
        self, fd: _FileDescriptorLike, callback: Callable[..., None], *args: Any
    ) -> None:
        self._readers[fd] = functools.partial(callback, *args)
        self._wake_selector()

    def add_writer(
        self, fd: _FileDescriptorLike, callback: Callable[..., None], *args: Any
    ) -> None:
        self._writers[fd] = functools.partial(callback, *args)
        self._wake_selector()

    def remove_reader(self, fd: _FileDescriptorLike) -> bool:
        try:
            del self._readers[fd]
        except KeyError:
            return False
        self._wake_selector()
        return True

    def remove_writer(self, fd: _FileDescriptorLike) -> bool:
        try:
            del self._writers[fd]
        except KeyError:
            return False
        self._wake_selector()
        return True


def _get_selector_windows(
    asyncio_loop: asyncio.AbstractEventLoop,
) -> SelectorThread:
    """Get selector-compatible loop.

    Sets ``add_reader`` family of methods on the asyncio loop.

    Workaround Windows proactor removal of *reader methods.
    """

    if asyncio_loop in _selectors:
        return _selectors[asyncio_loop]

    find_root_task().add_done_callback(_at_loop_close_callback)
    selector_thread = _selectors[asyncio_loop] = SelectorThread(asyncio_loop)

    # patch loop.close to also close the selector thread
    loop_close = asyncio_loop.close

    def _close_selector_and_loop() -> None:
        # restore original before calling selector.close,
        # which in turn calls eventloop.close!
        asyncio_loop.close = loop_close  # type: ignore[method-assign]
        _selectors.pop(asyncio_loop, None)
        selector_thread.close()
        asyncio_loop.close()

    asyncio_loop.close = _close_selector_and_loop  # type: ignore[method-assign]

    return selector_thread

1	"""Ensure asyncio selector methods (add_reader, etc.) are available.
2	Running select in a thread and defining these methods on the running event loop.
3	Originally in tornado.platform.asyncio.
4	Redistributed under license Apache-2.0
5	"""
6
7	from __future__ import annotations	2✔
8
9	import asyncio	2✔
10	import errno	2✔
11	import functools	2✔
12	import select	2✔
13	import socket	2✔
14	import threading	2✔
15	import typing	2✔
16	from typing import (	2✔
17	TYPE_CHECKING,
18	Any,
19	Callable,
20	Union,
21	)
22	from weakref import WeakKeyDictionary	2✔
23
24	from ._asyncio import find_root_task	2✔
25
26	if TYPE_CHECKING:	2✔
NEW 27	from _typeshed import HasFileno	×
28
NEW 29	_FileDescriptorLike = HasFileno \| int	×
30
31
32	# registry of asyncio loop : selector thread
33	_selectors: WeakKeyDictionary = WeakKeyDictionary()	2✔
34
35	# Collection of selector thread event loops to shut down on exit.
36	_selector_loops: set[SelectorThread] = set()	2✔
37
38
39	def _at_loop_close_callback(future: asyncio.Future) -> None:	2✔
40	for loop in _selector_loops:	2✔
41	with loop._select_cond:	2✔
42	loop._closing_selector = True	2✔
43	loop._select_cond.notify()	2✔
44	try:	2✔
45	loop._waker_w.send(b"a")	2✔
NEW 46	except BlockingIOError:	×
NEW 47	pass	×
48	# If we don't join our (daemon) thread here, we may get a deadlock
49	# during interpreter shutdown. I don't really understand why. This
50	# deadlock happens every time in CI (both travis and appveyor) but
51	# I've never been able to reproduce locally.
52	assert loop._thread is not None	2✔
53	loop._thread.join()	2✔
54	_selector_loops.clear()	2✔
55
56
57	# SelectorThread from tornado 6.4.0
58	class SelectorThread:	2✔
59	"""Define ``add_reader`` methods to be called in a background select thread.
60
61	Instances of this class start a second thread to run a selector.
62	This thread is completely hidden from the user;
63	all callbacks are run on the wrapped event loop's thread.
64
65	Typically used via ``AddThreadSelectorEventLoop``,
66	but can be attached to a running asyncio loop.
67	"""
68
69	_closed = False	2✔
70
71	def __init__(self, real_loop: asyncio.AbstractEventLoop) -> None:	2✔
72	self._real_loop = real_loop	2✔
73
74	self._select_cond = threading.Condition()	2✔
75	self._select_args: (	2✔
76	tuple[list[_FileDescriptorLike], list[_FileDescriptorLike]] \| None
77	) = None
78	self._closing_selector = False	2✔
79	self._thread: threading.Thread \| None = None	2✔
80
81	self._readers: dict[_FileDescriptorLike, Callable] = {}	2✔
82	self._writers: dict[_FileDescriptorLike, Callable] = {}	2✔
83
84	# Writing to _waker_w will wake up the selector thread, which
85	# watches for _waker_r to be readable.
86	self._waker_r, self._waker_w = socket.socketpair()	2✔
87	self._waker_r.setblocking(False)	2✔
88	self._waker_w.setblocking(False)	2✔
89	_selector_loops.add(self)	2✔
90	self.add_reader(self._waker_r, self._consume_waker)	2✔
91	self._thread_manager()	2✔
92
93	def close(self) -> None:	2✔
94	if self._closed:	2✔
NEW 95	return	×
96	with self._select_cond:	2✔
97	self._closing_selector = True	2✔
98	self._select_cond.notify()	2✔
99	self._wake_selector()	2✔
100	if self._thread is not None:	2✔
101	self._thread.join()	2✔
102	_selector_loops.discard(self)	2✔
103	self.remove_reader(self._waker_r)	2✔
104	self._waker_r.close()	2✔
105	self._waker_w.close()	2✔
106	self._closed = True	2✔
107
108	def _thread_manager(self) -> None:	2✔
109	# Create a thread to run the select system call. We manage this thread
110	# manually so we can trigger a clean shutdown at loop teardown. Note
111	# that due to the order of operations at shutdown, only daemon threads
112	# can be shut down in this way (non-daemon threads would require the
113	# introduction of a new hook: https://bugs.python.org/issue41962)
114	self._thread = threading.Thread(	2✔
115	name="AnyIO selector",
116	daemon=True,
117	target=self._run_select,
118	)
119	self._thread.start()	2✔
120	self._start_select()	2✔
121
122	def _wake_selector(self) -> None:	2✔
123	if self._closed:	2✔
NEW 124	return	×
125	try:	2✔
126	self._waker_w.send(b"a")	2✔
NEW 127	except BlockingIOError:	×
NEW 128	pass	×
129
130	def _consume_waker(self) -> None:	2✔
131	try:	2✔
132	self._waker_r.recv(1024)	2✔
NEW 133	except BlockingIOError:	×
NEW 134	pass	×
135
136	def _start_select(self) -> None:	2✔
137	# Capture reader and writer sets here in the event loop
138	# thread to avoid any problems with concurrent
139	# modification while the select loop uses them.
140	with self._select_cond:	2✔
141	assert self._select_args is None	2✔
142	self._select_args = (list(self._readers.keys()), list(self._writers.keys()))	2✔
143	self._select_cond.notify()	2✔
144
145	def _run_select(self) -> None:	2✔
146	while True:	1✔
147	with self._select_cond:	2✔
148	while self._select_args is None and not self._closing_selector:	2✔
149	self._select_cond.wait()	2✔
150	if self._closing_selector:	2✔
151	return	2✔
152	assert self._select_args is not None	2✔
153	to_read, to_write = self._select_args	2✔
154	self._select_args = None	2✔
155
156	# We use the simpler interface of the select module instead of
157	# the more stateful interface in the selectors module because
158	# this class is only intended for use on windows, where
159	# select.select is the only option. The selector interface
160	# does not have well-documented thread-safety semantics that
161	# we can rely on so ensuring proper synchronization would be
162	# tricky.
163	try:	2✔
164	# On windows, selecting on a socket for write will not
165	# return the socket when there is an error (but selecting
166	# for reads works). Also select for errors when selecting
167	# for writes, and merge the results.
168	#
169	# This pattern is also used in
170	# https://github.com/python/cpython/blob/v3.8.0/Lib/selectors.py#L312-L317
171	rs, ws, xs = select.select(to_read, to_write, to_write)	2✔
172	ws = ws + xs	2✔
NEW 173	except OSError as e:	×
174	# After remove_reader or remove_writer is called, the file
175	# descriptor may subsequently be closed on the event loop
176	# thread. It's possible that this select thread hasn't
177	# gotten into the select system call by the time that
178	# happens in which case (at least on macOS), select may
179	# raise a "bad file descriptor" error. If we get that
180	# error, check and see if we're also being woken up by
181	# polling the waker alone. If we are, just return to the
182	# event loop and we'll get the updated set of file
183	# descriptors on the next iteration. Otherwise, raise the
184	# original error.
NEW 185	if e.errno == getattr(errno, "WSAENOTSOCK", errno.EBADF):	×
NEW 186	rs, _, _ = select.select([self._waker_r.fileno()], [], [], 0)	×
NEW 187	if rs:	×
NEW 188	ws = []	×
189	else:
NEW 190	raise	×
191	else:
NEW 192	raise	×
193
194	try:	2✔
195	self._real_loop.call_soon_threadsafe(self._handle_select, rs, ws)	2✔
NEW 196	except RuntimeError:	×
197	# "Event loop is closed". Swallow the exception for
198	# consistency with PollIOLoop (and logical consistency
199	# with the fact that we can't guarantee that an
200	# add_callback that completes without error will
201	# eventually execute).
NEW 202	pass	×
NEW 203	except AttributeError:	×
204	# ProactorEventLoop may raise this instead of RuntimeError
205	# if call_soon_threadsafe races with a call to close().
206	# Swallow it too for consistency.
NEW 207	pass	×
208
209	def _handle_select(	2✔
210	self, rs: list[_FileDescriptorLike], ws: list[_FileDescriptorLike]
211	) -> None:
212	for r in rs:	2✔
213	self._handle_event(r, self._readers)	2✔
214	for w in ws:	2✔
215	self._handle_event(w, self._writers)	2✔
216	self._start_select()	2✔
217
218	def _handle_event(	2✔
219	self,
220	fd: _FileDescriptorLike,
221	cb_map: dict[_FileDescriptorLike, Callable],
222	) -> None:
223	try:	2✔
224	callback = cb_map[fd]	2✔
225	except KeyError:	2✔
226	return	2✔
227	callback()	2✔
228
229	def add_reader(	2✔
230	self, fd: _FileDescriptorLike, callback: Callable[..., None], *args: Any
231	) -> None:
232	self._readers[fd] = functools.partial(callback, *args)	2✔
233	self._wake_selector()	2✔
234
235	def add_writer(	2✔
236	self, fd: _FileDescriptorLike, callback: Callable[..., None], *args: Any
237	) -> None:
238	self._writers[fd] = functools.partial(callback, *args)	2✔
239	self._wake_selector()	2✔
240
241	def remove_reader(self, fd: _FileDescriptorLike) -> bool:	2✔
242	try:	2✔
243	del self._readers[fd]	2✔
NEW 244	except KeyError:	×
NEW 245	return False	×
246	self._wake_selector()	2✔
247	return True	2✔
248
249	def remove_writer(self, fd: _FileDescriptorLike) -> bool:	2✔
250	try:	2✔
251	del self._writers[fd]	2✔
NEW 252	except KeyError:	×
NEW 253	return False	×
254	self._wake_selector()	2✔
255	return True	2✔
256
257
258	def _get_selector_windows(	2✔
259	asyncio_loop: asyncio.AbstractEventLoop,
260	) -> SelectorThread:
261	"""Get selector-compatible loop.
262
263	Sets ``add_reader`` family of methods on the asyncio loop.
264
265	Workaround Windows proactor removal of *reader methods.
266	"""
267
268	if asyncio_loop in _selectors:	2✔
NEW 269	return _selectors[asyncio_loop]	×
270
271	find_root_task().add_done_callback(_at_loop_close_callback)	2✔
272	selector_thread = _selectors[asyncio_loop] = SelectorThread(asyncio_loop)	2✔
273
274	# patch loop.close to also close the selector thread
275	loop_close = asyncio_loop.close	2✔
276
277	def _close_selector_and_loop() -> None:	2✔
278	# restore original before calling selector.close,
279	# which in turn calls eventloop.close!
280	asyncio_loop.close = loop_close # type: ignore[method-assign]	2✔
281	_selectors.pop(asyncio_loop, None)	2✔
282	selector_thread.close()	2✔
283	asyncio_loop.close()	2✔
284
285	asyncio_loop.close = _close_selector_and_loop # type: ignore[method-assign]	2✔
286
287	return selector_thread	2✔

agronholm / anyio / 11890040966

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