cpython/Lib/asyncio/events.py

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"""Event loop and event loop policy."""
__all__ = ['AbstractEventLoopPolicy', 'DefaultEventLoopPolicy',
'AbstractEventLoop', 'AbstractServer',
'Handle', 'TimerHandle',
'get_event_loop_policy', 'set_event_loop_policy',
'get_event_loop', 'set_event_loop', 'new_event_loop',
]
import subprocess
import sys
import threading
import socket
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from .log import logger
class Handle:
"""Object returned by callback registration methods."""
def __init__(self, callback, args):
self._callback = callback
self._args = args
self._cancelled = False
def __repr__(self):
res = 'Handle({}, {})'.format(self._callback, self._args)
if self._cancelled:
res += '<cancelled>'
return res
def cancel(self):
self._cancelled = True
def _run(self):
try:
self._callback(*self._args)
except Exception:
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logger.exception('Exception in callback %s %r',
self._callback, self._args)
self = None # Needed to break cycles when an exception occurs.
def make_handle(callback, args):
# TODO: Inline this?
assert not isinstance(callback, Handle), 'A Handle is not a callback'
return Handle(callback, args)
class TimerHandle(Handle):
"""Object returned by timed callback registration methods."""
def __init__(self, when, callback, args):
assert when is not None
super().__init__(callback, args)
self._when = when
def __repr__(self):
res = 'TimerHandle({}, {}, {})'.format(self._when,
self._callback,
self._args)
if self._cancelled:
res += '<cancelled>'
return res
def __hash__(self):
return hash(self._when)
def __lt__(self, other):
return self._when < other._when
def __le__(self, other):
if self._when < other._when:
return True
return self.__eq__(other)
def __gt__(self, other):
return self._when > other._when
def __ge__(self, other):
if self._when > other._when:
return True
return self.__eq__(other)
def __eq__(self, other):
if isinstance(other, TimerHandle):
return (self._when == other._when and
self._callback == other._callback and
self._args == other._args and
self._cancelled == other._cancelled)
return NotImplemented
def __ne__(self, other):
equal = self.__eq__(other)
return NotImplemented if equal is NotImplemented else not equal
class AbstractServer:
"""Abstract server returned by create_service()."""
def close(self):
"""Stop serving. This leaves existing connections open."""
return NotImplemented
def wait_closed(self):
"""Coroutine to wait until service is closed."""
return NotImplemented
class AbstractEventLoop:
"""Abstract event loop."""
# Running and stopping the event loop.
def run_forever(self):
"""Run the event loop until stop() is called."""
raise NotImplementedError
def run_until_complete(self, future):
"""Run the event loop until a Future is done.
Return the Future's result, or raise its exception.
"""
raise NotImplementedError
def stop(self):
"""Stop the event loop as soon as reasonable.
Exactly how soon that is may depend on the implementation, but
no more I/O callbacks should be scheduled.
"""
raise NotImplementedError
def is_running(self):
"""Return whether the event loop is currently running."""
raise NotImplementedError
# Methods scheduling callbacks. All these return Handles.
def call_soon(self, callback, *args):
return self.call_later(0, callback, *args)
def call_later(self, delay, callback, *args):
raise NotImplementedError
def call_at(self, when, callback, *args):
raise NotImplementedError
def time(self):
raise NotImplementedError
# Methods for interacting with threads.
def call_soon_threadsafe(self, callback, *args):
raise NotImplementedError
def run_in_executor(self, executor, callback, *args):
raise NotImplementedError
def set_default_executor(self, executor):
raise NotImplementedError
# Network I/O methods returning Futures.
def getaddrinfo(self, host, port, *, family=0, type=0, proto=0, flags=0):
raise NotImplementedError
def getnameinfo(self, sockaddr, flags=0):
raise NotImplementedError
def create_connection(self, protocol_factory, host=None, port=None, *,
ssl=None, family=0, proto=0, flags=0, sock=None,
local_addr=None):
raise NotImplementedError
def create_server(self, protocol_factory, host=None, port=None, *,
family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE,
sock=None, backlog=100, ssl=None, reuse_address=None):
"""A coroutine which creates a TCP server bound to host and port.
The return value is a Server object which can be used to stop
the service.
If host is an empty string or None all interfaces are assumed
and a list of multiple sockets will be returned (most likely
one for IPv4 and another one for IPv6).
family can be set to either AF_INET or AF_INET6 to force the
socket to use IPv4 or IPv6. If not set it will be determined
from host (defaults to AF_UNSPEC).
flags is a bitmask for getaddrinfo().
sock can optionally be specified in order to use a preexisting
socket object.
backlog is the maximum number of queued connections passed to
listen() (defaults to 100).
ssl can be set to an SSLContext to enable SSL over the
accepted connections.
reuse_address tells the kernel to reuse a local socket in
TIME_WAIT state, without waiting for its natural timeout to
expire. If not specified will automatically be set to True on
UNIX.
"""
raise NotImplementedError
def create_datagram_endpoint(self, protocol_factory,
local_addr=None, remote_addr=None, *,
family=0, proto=0, flags=0):
raise NotImplementedError
def connect_read_pipe(self, protocol_factory, pipe):
"""Register read pipe in eventloop.
protocol_factory should instantiate object with Protocol interface.
pipe is file-like object already switched to nonblocking.
Return pair (transport, protocol), where transport support
ReadTransport ABC"""
# The reason to accept file-like object instead of just file descriptor
# is: we need to own pipe and close it at transport finishing
# Can got complicated errors if pass f.fileno(),
# close fd in pipe transport then close f and vise versa.
raise NotImplementedError
def connect_write_pipe(self, protocol_factory, pipe):
"""Register write pipe in eventloop.
protocol_factory should instantiate object with BaseProtocol interface.
Pipe is file-like object already switched to nonblocking.
Return pair (transport, protocol), where transport support
WriteTransport ABC"""
# The reason to accept file-like object instead of just file descriptor
# is: we need to own pipe and close it at transport finishing
# Can got complicated errors if pass f.fileno(),
# close fd in pipe transport then close f and vise versa.
raise NotImplementedError
def subprocess_shell(self, protocol_factory, cmd, *, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.PIPE,
**kwargs):
raise NotImplementedError
def subprocess_exec(self, protocol_factory, *args, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.PIPE,
**kwargs):
raise NotImplementedError
# Ready-based callback registration methods.
# The add_*() methods return None.
# The remove_*() methods return True if something was removed,
# False if there was nothing to delete.
def add_reader(self, fd, callback, *args):
raise NotImplementedError
def remove_reader(self, fd):
raise NotImplementedError
def add_writer(self, fd, callback, *args):
raise NotImplementedError
def remove_writer(self, fd):
raise NotImplementedError
# Completion based I/O methods returning Futures.
def sock_recv(self, sock, nbytes):
raise NotImplementedError
def sock_sendall(self, sock, data):
raise NotImplementedError
def sock_connect(self, sock, address):
raise NotImplementedError
def sock_accept(self, sock):
raise NotImplementedError
# Signal handling.
def add_signal_handler(self, sig, callback, *args):
raise NotImplementedError
def remove_signal_handler(self, sig):
raise NotImplementedError
class AbstractEventLoopPolicy:
"""Abstract policy for accessing the event loop."""
def get_event_loop(self):
"""XXX"""
raise NotImplementedError
def set_event_loop(self, loop):
"""XXX"""
raise NotImplementedError
def new_event_loop(self):
"""XXX"""
raise NotImplementedError
class DefaultEventLoopPolicy(threading.local, AbstractEventLoopPolicy):
"""Default policy implementation for accessing the event loop.
In this policy, each thread has its own event loop. However, we
only automatically create an event loop by default for the main
thread; other threads by default have no event loop.
Other policies may have different rules (e.g. a single global
event loop, or automatically creating an event loop per thread, or
using some other notion of context to which an event loop is
associated).
"""
_loop = None
_set_called = False
def get_event_loop(self):
"""Get the event loop.
This may be None or an instance of EventLoop.
"""
if (self._loop is None and
not self._set_called and
isinstance(threading.current_thread(), threading._MainThread)):
self._loop = self.new_event_loop()
assert self._loop is not None, \
('There is no current event loop in thread %r.' %
threading.current_thread().name)
return self._loop
def set_event_loop(self, loop):
"""Set the event loop."""
# TODO: The isinstance() test violates the PEP.
self._set_called = True
assert loop is None or isinstance(loop, AbstractEventLoop)
self._loop = loop
def new_event_loop(self):
"""Create a new event loop.
You must call set_event_loop() to make this the current event
loop.
"""
if sys.platform == 'win32': # pragma: no cover
from . import windows_events
return windows_events.SelectorEventLoop()
else: # pragma: no cover
from . import unix_events
return unix_events.SelectorEventLoop()
# Event loop policy. The policy itself is always global, even if the
# policy's rules say that there is an event loop per thread (or other
# notion of context). The default policy is installed by the first
# call to get_event_loop_policy().
_event_loop_policy = None
def get_event_loop_policy():
"""XXX"""
global _event_loop_policy
if _event_loop_policy is None:
_event_loop_policy = DefaultEventLoopPolicy()
return _event_loop_policy
def set_event_loop_policy(policy):
"""XXX"""
global _event_loop_policy
# TODO: The isinstance() test violates the PEP.
assert policy is None or isinstance(policy, AbstractEventLoopPolicy)
_event_loop_policy = policy
def get_event_loop():
"""XXX"""
return get_event_loop_policy().get_event_loop()
def set_event_loop(loop):
"""XXX"""
get_event_loop_policy().set_event_loop(loop)
def new_event_loop():
"""XXX"""
return get_event_loop_policy().new_event_loop()