Current File : //lib/python3/dist-packages/twisted/internet/asyncioreactor.py
# -*- test-case-name: twisted.test.test_internet -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
asyncio-based reactor implementation.
"""
import errno
import sys
from asyncio import AbstractEventLoop, get_event_loop
from typing import Dict, Optional, Type
from zope.interface import implementer
from twisted.internet.abstract import FileDescriptor
from twisted.internet.interfaces import IReactorFDSet
from twisted.internet.posixbase import (
_NO_FILEDESC,
PosixReactorBase,
_ContinuousPolling,
)
from twisted.logger import Logger
from twisted.python.log import callWithLogger
@implementer(IReactorFDSet)
class AsyncioSelectorReactor(PosixReactorBase):
"""
Reactor running on top of L{asyncio.SelectorEventLoop}.
On POSIX platforms, the default event loop is
L{asyncio.SelectorEventLoop}.
On Windows, the default event loop on Python 3.7 and older
is C{asyncio.WindowsSelectorEventLoop}, but on Python 3.8 and newer
the default event loop is C{asyncio.WindowsProactorEventLoop} which
is incompatible with L{AsyncioSelectorReactor}.
Applications that use L{AsyncioSelectorReactor} on Windows
with Python 3.8+ must call
C{asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())}
before instantiating and running L{AsyncioSelectorReactor}.
"""
_asyncClosed = False
_log = Logger()
def __init__(self, eventloop: Optional[AbstractEventLoop] = None):
if eventloop is None:
_eventloop: AbstractEventLoop = get_event_loop()
else:
_eventloop = eventloop
# On Python 3.8+, asyncio.get_event_loop() on
# Windows was changed to return a ProactorEventLoop
# unless the loop policy has been changed.
if sys.platform == "win32":
from asyncio import ProactorEventLoop
if isinstance(_eventloop, ProactorEventLoop):
raise TypeError(
f"ProactorEventLoop is not supported, got: {_eventloop}"
)
self._asyncioEventloop: AbstractEventLoop = _eventloop
self._writers: Dict[Type[FileDescriptor], int] = {}
self._readers: Dict[Type[FileDescriptor], int] = {}
self._continuousPolling = _ContinuousPolling(self)
self._scheduledAt = None
self._timerHandle = None
super().__init__()
def _unregisterFDInAsyncio(self, fd):
"""
Compensate for a bug in asyncio where it will not unregister a FD that
it cannot handle in the epoll loop. It touches internal asyncio code.
A description of the bug by markrwilliams:
The C{add_writer} method of asyncio event loops isn't atomic because
all the Selector classes in the selector module internally record a
file object before passing it to the platform's selector
implementation. If the platform's selector decides the file object
isn't acceptable, the resulting exception doesn't cause the Selector to
un-track the file object.
The failing/hanging stdio test goes through the following sequence of
events (roughly):
* The first C{connection.write(intToByte(value))} call hits the asyncio
reactor's C{addWriter} method.
* C{addWriter} calls the asyncio loop's C{add_writer} method, which
happens to live on C{_BaseSelectorEventLoop}.
* The asyncio loop's C{add_writer} method checks if the file object has
been registered before via the selector's C{get_key} method.
* It hasn't, so the KeyError block runs and calls the selector's
register method
* Code examples that follow use EpollSelector, but the code flow holds
true for any other selector implementation. The selector's register
method first calls through to the next register method in the MRO
* That next method is always C{_BaseSelectorImpl.register} which
creates a C{SelectorKey} instance for the file object, stores it under
the file object's file descriptor, and then returns it.
* Control returns to the concrete selector implementation, which asks
the operating system to track the file descriptor using the right API.
* The operating system refuses! An exception is raised that, in this
case, the asyncio reactor handles by creating a C{_ContinuousPolling}
object to watch the file descriptor.
* The second C{connection.write(intToByte(value))} call hits the
asyncio reactor's C{addWriter} method, which hits the C{add_writer}
method. But the loop's selector's get_key method now returns a
C{SelectorKey}! Now the asyncio reactor's C{addWriter} method thinks
the asyncio loop will watch the file descriptor, even though it won't.
"""
try:
self._asyncioEventloop._selector.unregister(fd)
except BaseException:
pass
def _readOrWrite(self, selectable, read):
method = selectable.doRead if read else selectable.doWrite
if selectable.fileno() == -1:
self._disconnectSelectable(selectable, _NO_FILEDESC, read)
return
try:
why = method()
except Exception as e:
why = e
self._log.failure(None)
if why:
self._disconnectSelectable(selectable, why, read)
def addReader(self, reader):
if reader in self._readers.keys() or reader in self._continuousPolling._readers:
return
fd = reader.fileno()
try:
self._asyncioEventloop.add_reader(
fd, callWithLogger, reader, self._readOrWrite, reader, True
)
self._readers[reader] = fd
except OSError as e:
self._unregisterFDInAsyncio(fd)
if e.errno == errno.EPERM:
# epoll(7) doesn't support certain file descriptors,
# e.g. filesystem files, so for those we just poll
# continuously:
self._continuousPolling.addReader(reader)
else:
raise
def addWriter(self, writer):
if writer in self._writers.keys() or writer in self._continuousPolling._writers:
return
fd = writer.fileno()
try:
self._asyncioEventloop.add_writer(
fd, callWithLogger, writer, self._readOrWrite, writer, False
)
self._writers[writer] = fd
except PermissionError:
self._unregisterFDInAsyncio(fd)
# epoll(7) doesn't support certain file descriptors,
# e.g. filesystem files, so for those we just poll
# continuously:
self._continuousPolling.addWriter(writer)
except BrokenPipeError:
# The kqueuereactor will raise this if there is a broken pipe
self._unregisterFDInAsyncio(fd)
except BaseException:
self._unregisterFDInAsyncio(fd)
raise
def removeReader(self, reader):
# First, see if they're trying to remove a reader that we don't have.
if not (
reader in self._readers.keys() or self._continuousPolling.isReading(reader)
):
# We don't have it, so just return OK.
return
# If it was a cont. polling reader, check there first.
if self._continuousPolling.isReading(reader):
self._continuousPolling.removeReader(reader)
return
fd = reader.fileno()
if fd == -1:
# If the FD is -1, we want to know what its original FD was, to
# remove it.
fd = self._readers.pop(reader)
else:
self._readers.pop(reader)
self._asyncioEventloop.remove_reader(fd)
def removeWriter(self, writer):
# First, see if they're trying to remove a writer that we don't have.
if not (
writer in self._writers.keys() or self._continuousPolling.isWriting(writer)
):
# We don't have it, so just return OK.
return
# If it was a cont. polling writer, check there first.
if self._continuousPolling.isWriting(writer):
self._continuousPolling.removeWriter(writer)
return
fd = writer.fileno()
if fd == -1:
# If the FD is -1, we want to know what its original FD was, to
# remove it.
fd = self._writers.pop(writer)
else:
self._writers.pop(writer)
self._asyncioEventloop.remove_writer(fd)
def removeAll(self):
return (
self._removeAll(self._readers.keys(), self._writers.keys())
+ self._continuousPolling.removeAll()
)
def getReaders(self):
return list(self._readers.keys()) + self._continuousPolling.getReaders()
def getWriters(self):
return list(self._writers.keys()) + self._continuousPolling.getWriters()
def iterate(self, timeout):
self._asyncioEventloop.call_later(timeout + 0.01, self._asyncioEventloop.stop)
self._asyncioEventloop.run_forever()
def run(self, installSignalHandlers=True):
self.startRunning(installSignalHandlers=installSignalHandlers)
self._asyncioEventloop.run_forever()
if self._justStopped:
self._justStopped = False
def stop(self):
super().stop()
# This will cause runUntilCurrent which in its turn
# will call fireSystemEvent("shutdown")
self.callLater(0, lambda: None)
def crash(self):
super().crash()
self._asyncioEventloop.stop()
def _onTimer(self):
self._scheduledAt = None
self.runUntilCurrent()
self._reschedule()
def _reschedule(self):
timeout = self.timeout()
if timeout is not None:
abs_time = self._asyncioEventloop.time() + timeout
self._scheduledAt = abs_time
if self._timerHandle is not None:
self._timerHandle.cancel()
self._timerHandle = self._asyncioEventloop.call_at(abs_time, self._onTimer)
def _moveCallLaterSooner(self, tple):
PosixReactorBase._moveCallLaterSooner(self, tple)
self._reschedule()
def callLater(self, seconds, f, *args, **kwargs):
dc = PosixReactorBase.callLater(self, seconds, f, *args, **kwargs)
abs_time = self._asyncioEventloop.time() + self.timeout()
if self._scheduledAt is None or abs_time < self._scheduledAt:
self._reschedule()
return dc
def callFromThread(self, f, *args, **kwargs):
g = lambda: self.callLater(0, f, *args, **kwargs)
self._asyncioEventloop.call_soon_threadsafe(g)
def install(eventloop=None):
"""
Install an asyncio-based reactor.
@param eventloop: The asyncio eventloop to wrap. If default, the global one
is selected.
"""
reactor = AsyncioSelectorReactor(eventloop)
from twisted.internet.main import installReactor
installReactor(reactor)
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