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| 1 | +"""Owned TCP admission without asyncio.Server's accept/close race (CPython #109564). |
| 2 | +
|
| 3 | +Only socket admission lives here. Identity, framing and established stream |
| 4 | +ownership belong to the shared collector listener. No event-loop monkeypatches. |
| 5 | +""" |
| 6 | + |
| 7 | +from __future__ import annotations |
| 8 | + |
| 9 | +import asyncio |
| 10 | +import errno |
| 11 | +import logging |
| 12 | +import socket |
| 13 | +from collections.abc import Awaitable, Callable |
| 14 | + |
| 15 | +from .common import _close_writer_bounded |
| 16 | + |
| 17 | +logger = logging.getLogger(__name__) |
| 18 | + |
| 19 | +_BACKLOG = 100 |
| 20 | +_MAX_ADMISSIONS = 100 |
| 21 | +_RESOURCE_ERRORS = {errno.EMFILE, errno.ENFILE, errno.ENOBUFS, errno.ENOMEM} |
| 22 | + |
| 23 | + |
| 24 | +class CollectorTcpAcceptor: |
| 25 | + """Accept, prepare and hand off streams; stop joins every uncommitted handoff.""" |
| 26 | + |
| 27 | + def __init__( |
| 28 | + self, |
| 29 | + sockets: list[socket.socket], |
| 30 | + handler: Callable[[asyncio.StreamReader, asyncio.StreamWriter], Awaitable[None]], |
| 31 | + ) -> None: |
| 32 | + self._sockets = sockets |
| 33 | + self._handler = handler |
| 34 | + self._loop = asyncio.get_running_loop() |
| 35 | + self._closing = False |
| 36 | + self._admissions: dict[asyncio.Task[None], socket.socket] = {} |
| 37 | + self._retry_handles: dict[socket.socket, asyncio.TimerHandle] = {} |
| 38 | + self._close_task: asyncio.Task[None] | None = None |
| 39 | + |
| 40 | + @classmethod |
| 41 | + async def start(cls, handler, host: str, port: int) -> CollectorTcpAcceptor: |
| 42 | + """Bind all resolved addresses, rolling back the whole bind on failure.""" |
| 43 | + loop = asyncio.get_running_loop() |
| 44 | + addresses = await loop.getaddrinfo( |
| 45 | + host or None, port, type=socket.SOCK_STREAM, flags=socket.AI_PASSIVE, |
| 46 | + ) |
| 47 | + sockets: list[socket.socket] = [] |
| 48 | + try: |
| 49 | + for family, sock_type, proto, _, address in dict.fromkeys(addresses): |
| 50 | + sock = socket.socket(family, sock_type, proto) |
| 51 | + sockets.append(sock) |
| 52 | + sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) |
| 53 | + if family == socket.AF_INET6: |
| 54 | + sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 1) |
| 55 | + sock.setblocking(False) |
| 56 | + sock.bind(address) |
| 57 | + sock.listen(_BACKLOG) |
| 58 | + if not sockets: |
| 59 | + raise OSError("collector_listener_no_bind_addresses") |
| 60 | + acceptor = cls(sockets, handler) |
| 61 | + try: |
| 62 | + for sock in sockets: |
| 63 | + acceptor._resume_accept(sock) |
| 64 | + except BaseException: |
| 65 | + acceptor.close() |
| 66 | + await acceptor.wait_closed() |
| 67 | + raise |
| 68 | + return acceptor |
| 69 | + except BaseException: |
| 70 | + for sock in sockets: |
| 71 | + sock.close() |
| 72 | + raise |
| 73 | + |
| 74 | + @property |
| 75 | + def sockets(self) -> tuple[socket.socket, ...]: |
| 76 | + return tuple(self._sockets) if not self._closing else () |
| 77 | + |
| 78 | + def _resume_accept(self, sock: socket.socket) -> None: |
| 79 | + self._retry_handles.pop(sock, None) |
| 80 | + if not self._closing: |
| 81 | + self._loop.add_reader(sock.fileno(), self._accept_ready, sock) |
| 82 | + |
| 83 | + def _accept_ready(self, sock: socket.socket) -> None: |
| 84 | + if self._closing: |
| 85 | + return |
| 86 | + # Acceptance and raw-socket ownership are synchronous. Cancelling an |
| 87 | + # await of sock_accept after its future completed could lose the result. |
| 88 | + for _ in range(_BACKLOG + 1): |
| 89 | + try: |
| 90 | + client, _ = sock.accept() |
| 91 | + except ConnectionAbortedError: |
| 92 | + continue |
| 93 | + except (BlockingIOError, InterruptedError): |
| 94 | + return |
| 95 | + except OSError as exc: |
| 96 | + # Back off resource exhaustion without a busy selector loop. |
| 97 | + # The retry remains owned/cancellable by this acceptor. |
| 98 | + self._loop.remove_reader(sock.fileno()) |
| 99 | + logger.warning("Collector listener cannot accept a socket: %s", exc) |
| 100 | + if exc.errno in _RESOURCE_ERRORS: |
| 101 | + self._retry_handles[sock] = self._loop.call_later(1, self._resume_accept, sock) |
| 102 | + else: |
| 103 | + self.close() |
| 104 | + return |
| 105 | + if self._closing or len(self._admissions) >= _MAX_ADMISSIONS: |
| 106 | + client.close() |
| 107 | + else: |
| 108 | + # The record exists outside the coroutine too: cancellation |
| 109 | + # before its first instruction must not leak the raw socket. |
| 110 | + admission = self._admit(client) |
| 111 | + try: |
| 112 | + client.setblocking(False) |
| 113 | + task = asyncio.create_task(admission, name="collector_tcp_admit") |
| 114 | + except BaseException: |
| 115 | + admission.close() |
| 116 | + client.close() |
| 117 | + raise |
| 118 | + self._admissions[task] = client |
| 119 | + task.add_done_callback(self._admission_done) |
| 120 | + |
| 121 | + async def _admit(self, client: socket.socket) -> None: |
| 122 | + writer: asyncio.StreamWriter | None = None |
| 123 | + handed_off = False |
| 124 | + try: |
| 125 | + # Public socket-to-stream API. Unlike start_server, this transport |
| 126 | + # has no asyncio.Server to attach to after it has been closed. |
| 127 | + reader, writer = await asyncio.open_connection(sock=client) |
| 128 | + if not self._closing: |
| 129 | + await self._handler(reader, writer) |
| 130 | + handed_off = True |
| 131 | + finally: |
| 132 | + if not handed_off: |
| 133 | + if writer is None: |
| 134 | + client.close() |
| 135 | + else: |
| 136 | + await _close_writer_bounded(writer) |
| 137 | + |
| 138 | + def _admission_done(self, task: asyncio.Task[None]) -> None: |
| 139 | + client = self._admissions.pop(task, None) |
| 140 | + if client is None: |
| 141 | + return |
| 142 | + if task.cancelled(): |
| 143 | + if client is not None: |
| 144 | + client.close() |
| 145 | + return |
| 146 | + error = task.exception() |
| 147 | + if error is not None: |
| 148 | + if client is not None: |
| 149 | + client.close() |
| 150 | + logger.error("Collector TCP admission failed", exc_info=error) |
| 151 | + |
| 152 | + def close(self) -> None: |
| 153 | + """Fence new handoffs before cancelling accept and closing bind sockets.""" |
| 154 | + if self._closing: |
| 155 | + return |
| 156 | + self._closing = True |
| 157 | + for retry in self._retry_handles.values(): |
| 158 | + retry.cancel() |
| 159 | + self._retry_handles.clear() |
| 160 | + for sock in self._sockets: |
| 161 | + self._loop.remove_reader(sock.fileno()) |
| 162 | + sock.close() |
| 163 | + for task in tuple(self._admissions): |
| 164 | + task.cancel() |
| 165 | + self._close_task = asyncio.create_task(self._drain(), name="collector_tcp_close") |
| 166 | + |
| 167 | + async def _drain(self) -> None: |
| 168 | + # Any already-queued readiness callback sees _closing before accept. |
| 169 | + tasks = tuple(self._admissions) |
| 170 | + await asyncio.gather(*tasks, return_exceptions=True) |
| 171 | + for task in tasks: |
| 172 | + self._admission_done(task) |
| 173 | + self._sockets.clear() |
| 174 | + |
| 175 | + async def wait_closed(self) -> None: |
| 176 | + if self._close_task is None: |
| 177 | + raise RuntimeError("collector_listener_close_not_started") |
| 178 | + cancelled = False |
| 179 | + while not self._close_task.done(): |
| 180 | + try: |
| 181 | + await asyncio.shield(self._close_task) |
| 182 | + except asyncio.CancelledError: |
| 183 | + cancelled = True |
| 184 | + self._close_task.result() |
| 185 | + if cancelled: |
| 186 | + raise asyncio.CancelledError |
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