import asyncio
import sys
from asyncio import AbstractEventLoop, AbstractEventLoopPolicy
from contextlib import suppress
from typing import Any, Callable, Dict, List, Optional, Sequence, Type
from warnings import catch_warnings, filterwarnings, warn
from twisted.internet import asyncioreactor, error
from twisted.internet.base import DelayedCall
from twisted.internet.protocol import ServerFactory
from twisted.internet.tcp import Port
from scrapy.exceptions import ScrapyDeprecationWarning
from scrapy.utils.misc import load_object
def listen_tcp(portrange: List[int], host: str, factory: ServerFactory) -> Port: # type: ignore[return]
"""Like reactor.listenTCP but tries different ports in a range."""
from twisted.internet import reactor
if len(portrange) > 2:
raise ValueError(f"invalid portrange: {portrange}")
if not portrange:
return reactor.listenTCP(0, factory, interface=host)
if len(portrange) == 1:
return reactor.listenTCP(portrange[0], factory, interface=host)
for x in range(portrange[0], portrange[1] + 1):
try:
return reactor.listenTCP(x, factory, interface=host)
except error.CannotListenError:
if x == portrange[1]:
raise
class CallLaterOnce:
"""Schedule a function to be called in the next reactor loop, but only if
it hasn't been already scheduled since the last time it ran.
"""
def __init__(self, func: Callable, *a: Any, **kw: Any):
self._func: Callable = func
self._a: Sequence[Any] = a
self._kw: Dict[str, Any] = kw
self._call: Optional[DelayedCall] = None
def schedule(self, delay: float = 0) -> None:
from twisted.internet import reactor
if self._call is None:
self._call = reactor.callLater(delay, self)
def cancel(self) -> None:
if self._call:
self._call.cancel()
def __call__(self) -> Any:
self._call = None
return self._func(*self._a, **self._kw)
def set_asyncio_event_loop_policy() -> None:
"""The policy functions from asyncio often behave unexpectedly,
so we restrict their use to the absolutely essential case.
This should only be used to install the reactor.
"""
_get_asyncio_event_loop_policy()
def get_asyncio_event_loop_policy() -> AbstractEventLoopPolicy:
warn(
"Call to deprecated function "
"scrapy.utils.reactor.get_asyncio_event_loop_policy().\n"
"\n"
"Please use get_event_loop, new_event_loop and set_event_loop"
" from asyncio instead, as the corresponding policy methods may lead"
" to unexpected behaviour.\n"
"This function is replaced by set_asyncio_event_loop_policy and"
" is meant to be used only when the reactor is being installed.",
category=ScrapyDeprecationWarning,
stacklevel=2,
)
return _get_asyncio_event_loop_policy()
def _get_asyncio_event_loop_policy() -> AbstractEventLoopPolicy:
policy = asyncio.get_event_loop_policy()
if (
sys.version_info >= (3, 8)
and sys.platform == "win32"
and not isinstance(policy, asyncio.WindowsSelectorEventLoopPolicy)
):
policy = asyncio.WindowsSelectorEventLoopPolicy()
asyncio.set_event_loop_policy(policy)
return policy
[docs]def install_reactor(reactor_path: str, event_loop_path: Optional[str] = None) -> None:
"""Installs the :mod:`~twisted.internet.reactor` with the specified
import path. Also installs the asyncio event loop with the specified import
path if the asyncio reactor is enabled"""
reactor_class = load_object(reactor_path)
if reactor_class is asyncioreactor.AsyncioSelectorReactor:
set_asyncio_event_loop_policy()
with suppress(error.ReactorAlreadyInstalledError):
event_loop = set_asyncio_event_loop(event_loop_path)
asyncioreactor.install(eventloop=event_loop)
else:
*module, _ = reactor_path.split(".")
installer_path = module + ["install"]
installer = load_object(".".join(installer_path))
with suppress(error.ReactorAlreadyInstalledError):
installer()
def _get_asyncio_event_loop() -> AbstractEventLoop:
return set_asyncio_event_loop(None)
def set_asyncio_event_loop(event_loop_path: Optional[str]) -> AbstractEventLoop:
"""Sets and returns the event loop with specified import path."""
if event_loop_path is not None:
event_loop_class: Type[AbstractEventLoop] = load_object(event_loop_path)
event_loop = event_loop_class()
asyncio.set_event_loop(event_loop)
else:
try:
with catch_warnings():
# In Python 3.10.9, 3.11.1, 3.12 and 3.13, a DeprecationWarning
# is emitted about the lack of a current event loop, because in
# Python 3.14 and later `get_event_loop` will raise a
# RuntimeError in that event. Because our code is already
# prepared for that future behavior, we ignore the deprecation
# warning.
filterwarnings(
"ignore",
message="There is no current event loop",
category=DeprecationWarning,
)
event_loop = asyncio.get_event_loop()
except RuntimeError:
# `get_event_loop` raises RuntimeError when called with no asyncio
# event loop yet installed in the following scenarios:
# - Previsibly on Python 3.14 and later.
# https://github.com/python/cpython/issues/100160#issuecomment-1345581902
event_loop = asyncio.new_event_loop()
asyncio.set_event_loop(event_loop)
return event_loop
def verify_installed_reactor(reactor_path: str) -> None:
"""Raises :exc:`Exception` if the installed
:mod:`~twisted.internet.reactor` does not match the specified import
path."""
from twisted.internet import reactor
reactor_class = load_object(reactor_path)
if not reactor.__class__ == reactor_class:
msg = (
"The installed reactor "
f"({reactor.__module__}.{reactor.__class__.__name__}) does not "
f"match the requested one ({reactor_path})"
)
raise Exception(msg)
def verify_installed_asyncio_event_loop(loop_path: str) -> None:
from twisted.internet import reactor
loop_class = load_object(loop_path)
if isinstance(reactor._asyncioEventloop, loop_class):
return
installed = (
f"{reactor._asyncioEventloop.__class__.__module__}"
f".{reactor._asyncioEventloop.__class__.__qualname__}"
)
specified = f"{loop_class.__module__}.{loop_class.__qualname__}"
raise Exception(
"Scrapy found an asyncio Twisted reactor already "
f"installed, and its event loop class ({installed}) does "
"not match the one specified in the ASYNCIO_EVENT_LOOP "
f"setting ({specified})"
)
def is_asyncio_reactor_installed() -> bool:
from twisted.internet import reactor
return isinstance(reactor, asyncioreactor.AsyncioSelectorReactor)