"""Base implementation of event loop.

The event loop can be broken up into a multiplexer (the part

responsible for notifying us of I/O events) and the event loop proper,

which wraps a multiplexer with functionality for scheduling callbacks,

immediately or at a given time in the future.

Whenever a public API takes a callback, subsequent positional

arguments will be passed to the callback if/when it is called. This

avoids the proliferation of trivial lambdas implementing closures.

Keyword arguments for the callback are not supported; this is a

conscious design decision, leaving the door open for keyword arguments

to modify the meaning of the API call itself.

"""

import collections

import collections.abc

import concurrent.futures

import functools

import heapq

import itertools

import os

import socket

import stat

import subprocess

import threading

import time

import traceback

import sys

import warnings

import weakref

try:

import ssl

except ImportError: # pragma: no cover

ssl = None

from . import constants

from . import coroutines

from . import events

from . import exceptions

from . import futures

from . import protocols

from . import sslproto

from . import staggered

from . import tasks

from . import transports

from . import trsock

from .log import logger

__all__ = 'BaseEventLoop',

# Minimum number of _scheduled timer handles before cleanup of

# cancelled handles is performed.

_MIN_SCHEDULED_TIMER_HANDLES = 100

# Minimum fraction of _scheduled timer handles that are cancelled

# before cleanup of cancelled handles is performed.

_MIN_CANCELLED_TIMER_HANDLES_FRACTION = 0.5

_HAS_IPv6 = hasattr(socket, 'AF_INET6')

# Maximum timeout passed to select to avoid OS limitations

MAXIMUM_SELECT_TIMEOUT = 24 * 3600

# Used for deprecation and removal of `loop.create_datagram_endpoint()`'s

# *reuse_address* parameter

_unset = object()

def _format_handle(handle):

cb = handle._callback

if isinstance(getattr(cb, '__self__', None), tasks.Task):

# format the task

return repr(cb.__self__)

else:

return str(handle)

def _format_pipe(fd):

if fd == subprocess.PIPE:

return '<pipe>'

elif fd == subprocess.STDOUT:

return '<stdout>'

else:

return repr(fd)

def _set_reuseport(sock):

if not hasattr(socket, 'SO_REUSEPORT'):

raise ValueError('reuse_port not supported by socket module')

else:

try:

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)

except OSError:

raise ValueError('reuse_port not supported by socket module, '

'SO_REUSEPORT defined but not implemented.')

def _ipaddr_info(host, port, family, type, proto, flowinfo=0, scopeid=0):

# Try to skip getaddrinfo if "host" is already an IP. Users might have

# handled name resolution in their own code and pass in resolved IPs.

if not hasattr(socket, 'inet_pton'):

return

if proto not in {0, socket.IPPROTO_TCP, socket.IPPROTO_UDP} or \

host is None:

return None

if type == socket.SOCK_STREAM:

proto = socket.IPPROTO_TCP

elif type == socket.SOCK_DGRAM:

proto = socket.IPPROTO_UDP

else:

return None

if port is None:

port = 0

elif isinstance(port, bytes) and port == b'':

port = 0

elif isinstance(port, str) and port == '':

port = 0

else:

# If port's a service name like "http", don't skip getaddrinfo.

try:

port = int(port)

except (TypeError, ValueError):

return None

if family == socket.AF_UNSPEC:

afs = [socket.AF_INET]

if _HAS_IPv6:

afs.append(socket.AF_INET6)

else:

afs = [family]

if isinstance(host, bytes):

host = host.decode('idna')

if '%' in host:

# Linux's inet_pton doesn't accept an IPv6 zone index after host,

# like '::1%lo0'.

return None

for af in afs:

try:

socket.inet_pton(af, host)

# The host has already been resolved.

if _HAS_IPv6 and af == socket.AF_INET6:

return af, type, proto, '', (host, port, flowinfo, scopeid)

else:

return af, type, proto, '', (host, port)

except OSError:

pass

# "host" is not an IP address.

return None

def _interleave_addrinfos(addrinfos, first_address_family_count=1):

"""Interleave list of addrinfo tuples by family."""

# Group addresses by family

addrinfos_by_family = collections.OrderedDict()

for addr in addrinfos:

family = addr[0]

if family not in addrinfos_by_family:

addrinfos_by_family[family] = []

addrinfos_by_family[family].append(addr)

addrinfos_lists = list(addrinfos_by_family.values())

reordered = []

if first_address_family_count > 1:

reordered.extend(addrinfos_lists[0][:first_address_family_count - 1])

del addrinfos_lists[0][:first_address_family_count - 1]

reordered.extend(

a for a in itertools.chain.from_iterable(

itertools.zip_longest(*addrinfos_lists)

) if a is not None)

return reordered

def _run_until_complete_cb(fut):

if not fut.cancelled():

exc = fut.exception()

if isinstance(exc, (SystemExit, KeyboardInterrupt)):

# Issue #22429: run_forever() already finished, no need to

# stop it.

return

futures._get_loop(fut).stop()

if hasattr(socket, 'TCP_NODELAY'):

def _set_nodelay(sock):

if (sock.family in {socket.AF_INET, socket.AF_INET6} and

sock.type == socket.SOCK_STREAM and

sock.proto == socket.IPPROTO_TCP):

sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)

else:

def _set_nodelay(sock):

pass

class _SendfileFallbackProtocol(protocols.Protocol):

def __init__(self, transp):

if not isinstance(transp, transports._FlowControlMixin):

raise TypeError("transport should be _FlowControlMixin instance")

self._transport = transp

self._proto = transp.get_protocol()

self._should_resume_reading = transp.is_reading()

self._should_resume_writing = transp._protocol_paused

transp.pause_reading()

transp.set_protocol(self)

if self._should_resume_writing:

self._write_ready_fut = self._transport._loop.create_future()

else:

self._write_ready_fut = None

async def drain(self):

if self._transport.is_closing():

raise ConnectionError("Connection closed by peer")

fut = self._write_ready_fut

if fut is None:

return

await fut

def connection_made(self, transport):

raise RuntimeError("Invalid state: "

"connection should have been established already.")

def connection_lost(self, exc):

if self._write_ready_fut is not None:

# Never happens if peer disconnects after sending the whole content

# Thus disconnection is always an exception from user perspective

if exc is None:

self._write_ready_fut.set_exception(

ConnectionError("Connection is closed by peer"))

else:

self._write_ready_fut.set_exception(exc)

self._proto.connection_lost(exc)

def pause_writing(self):

if self._write_ready_fut is not None:

return

self._write_ready_fut = self._transport._loop.create_future()

def resume_writing(self):

if self._write_ready_fut is None:

return

self._write_ready_fut.set_result(False)

self._write_ready_fut = None

def data_received(self, data):

raise RuntimeError("Invalid state: reading should be paused")

def eof_received(self):

raise RuntimeError("Invalid state: reading should be paused")

async def restore(self):

self._transport.set_protocol(self._proto)

if self._should_resume_reading:

self._transport.resume_reading()

if self._write_ready_fut is not None:

# Cancel the future.

# Basically it has no effect because protocol is switched back,

# no code should wait for it anymore.

self._write_ready_fut.cancel()

if self._should_resume_writing:

self._proto.resume_writing()

class Server(events.AbstractServer):

def __init__(self, loop, sockets, protocol_factory, ssl_context, backlog,

ssl_handshake_timeout):

self._loop = loop

self._sockets = sockets

self._active_count = 0

self._waiters = []

self._protocol_factory = protocol_factory

self._backlog = backlog

self._ssl_context = ssl_context

self._ssl_handshake_timeout = ssl_handshake_timeout

self._serving = False

self._serving_forever_fut = None

def __repr__(self):

return f'<{self.__class__.__name__} sockets={self.sockets!r}>'

def _attach(self):

assert self._sockets is not None

self._active_count += 1

def _detach(self):

assert self._active_count > 0

self._active_count -= 1

if self._active_count == 0 and self._sockets is None:

self._wakeup()

def _wakeup(self):

waiters = self._waiters

self._waiters = None

for waiter in waiters:

if not waiter.done():

waiter.set_result(waiter)

def _start_serving(self):

if self._serving:

return

self._serving = True

for sock in self._sockets:

sock.listen(self._backlog)

self._loop._start_serving(

self._protocol_factory, sock, self._ssl_context,

self, self._backlog, self._ssl_handshake_timeout)

def get_loop(self):

return self._loop

def is_serving(self):

return self._serving

@property

def sockets(self):

if self._sockets is None:

return ()

return tuple(trsock.TransportSocket(s) for s in self._sockets)

def close(self):

sockets = self._sockets

if sockets is None:

return

self._sockets = None

for sock in sockets:

self._loop._stop_serving(sock)

self._serving = False

if (self._serving_forever_fut is not None and

not self._serving_forever_fut.done()):

self._serving_forever_fut.cancel()

self._serving_forever_fut = None

if self._active_count == 0:

self._wakeup()

async def start_serving(self):

self._start_serving()

# Skip one loop iteration so that all 'loop.add_reader'

# go through.

await tasks.sleep(0, loop=self._loop)

async def serve_forever(self):

if self._serving_forever_fut is not None:

raise RuntimeError(

f'server {self!r} is already being awaited on serve_forever()')

if self._sockets is None:

raise RuntimeError(f'server {self!r} is closed')

self._start_serving()

self._serving_forever_fut = self._loop.create_future()

try:

await self._serving_forever_fut

except exceptions.CancelledError:

try:

self.close()

await self.wait_closed()

finally:

raise

finally:

self._serving_forever_fut = None

async def wait_closed(self):

if self._sockets is None or self._waiters is None:

return

waiter = self._loop.create_future()

self._waiters.append(waiter)

await waiter

class BaseEventLoop(events.AbstractEventLoop):

def __init__(self):

self._timer_cancelled_count = 0

self._closed = False

self._stopping = False

self._ready = collections.deque()

self._scheduled = []

self._default_executor = None

self._internal_fds = 0

# Identifier of the thread running the event loop, or None if the

# event loop is not running

self._thread_id = None

self._clock_resolution = time.get_clock_info('monotonic').resolution

self._exception_handler = None

self.set_debug(coroutines._is_debug_mode())

# In debug mode, if the execution of a callback or a step of a task

# exceed this duration in seconds, the slow callback/task is logged.

self.slow_callback_duration = 0.1

self._current_handle = None

self._task_factory = None

self._coroutine_origin_tracking_enabled = False

self._coroutine_origin_tracking_saved_depth = None

# A weak set of all asynchronous generators that are

# being iterated by the loop.

self._asyncgens = weakref.WeakSet()

# Set to True when `loop.shutdown_asyncgens` is called.

self._asyncgens_shutdown_called = False

def __repr__(self):

return (

f'<{self.__class__.__name__} running={self.is_running()} '

f'closed={self.is_closed()} debug={self.get_debug()}>'

)

def create_future(self):

"""Create a Future object attached to the loop."""

return futures.Future(loop=self)

def create_task(self, coro, *, name=None):

"""Schedule a coroutine object.

Return a task object.

"""

self._check_closed()

if self._task_factory is None:

task = tasks.Task(coro, loop=self, name=name)

if task._source_traceback:

del task._source_traceback[-1]

else:

task = self._task_factory(self, coro)

tasks._set_task_name(task, name)

return task

def set_task_factory(self, factory):

"""Set a task factory that will be used by loop.create_task().

If factory is None the default task factory will be set.

If factory is a callable, it should have a signature matching

'(loop, coro)', where 'loop' will be a reference to the active

event loop, 'coro' will be a coroutine object. The callable

must return a Future.

"""

if factory is not None and not callable(factory):

raise TypeError('task factory must be a callable or None')

self._task_factory = factory

def get_task_factory(self):

"""Return a task factory, or None if the default one is in use."""

return self._task_factory

def _make_socket_transport(self, sock, protocol, waiter=None, *,

extra=None, server=None):

"""Create socket transport."""

raise NotImplementedError

def _make_ssl_transport(

self, rawsock, protocol, sslcontext, waiter=None,

*, server_side=False, server_hostname=None,

extra=None, server=None,

ssl_handshake_timeout=None,

call_connection_made=True):

"""Create SSL transport."""

raise NotImplementedError

def _make_datagram_transport(self, sock, protocol,

address=None, waiter=None, extra=None):

"""Create datagram transport."""

raise NotImplementedError

def _make_read_pipe_transport(self, pipe, protocol, waiter=None,

extra=None):

"""Create read pipe transport."""

raise NotImplementedError

def _make_write_pipe_transport(self, pipe, protocol, waiter=None,

extra=None):

"""Create write pipe transport."""

raise NotImplementedError

async def _make_subprocess_transport(self, protocol, args, shell,

stdin, stdout, stderr, bufsize,

extra=None, **kwargs):

"""Create subprocess transport."""

raise NotImplementedError

def _write_to_self(self):

"""Write a byte to self-pipe, to wake up the event loop.

This may be called from a different thread.

The subclass is responsible for implementing the self-pipe.

"""

raise NotImplementedError

def _process_events(self, event_list):

"""Process selector events."""

raise NotImplementedError

def _check_closed(self):

if self._closed:

raise RuntimeError('Event loop is closed')

def _asyncgen_finalizer_hook(self, agen):

self._asyncgens.discard(agen)

if not self.is_closed():

self.call_soon_threadsafe(self.create_task, agen.aclose())

def _asyncgen_firstiter_hook(self, agen):

if self._asyncgens_shutdown_called:

warnings.warn(

f"asynchronous generator {agen!r} was scheduled after "

f"loop.shutdown_asyncgens() call",

ResourceWarning, source=self)

self._asyncgens.add(agen)

async def shutdown_asyncgens(self):

"""Shutdown all active asynchronous generators."""

self._asyncgens_shutdown_called = True

if not len(self._asyncgens):

# If Python version is <3.6 or we don't have any asynchronous

# generators alive.

return

closing_agens = list(self._asyncgens)

self._asyncgens.clear()

results = await tasks.gather(

*[ag.aclose() for ag in closing_agens],

return_exceptions=True,

loop=self)

for result, agen in zip(results, closing_agens):

if isinstance(result, Exception):

self.call_exception_handler({

'message': f'an error occurred during closing of '

f'asynchronous generator {agen!r}',

'exception': result,

'asyncgen': agen

})

def _check_running(self):

if self.is_running():

raise RuntimeError('This event loop is already running')

if events._get_running_loop() is not None:

raise RuntimeError(

'Cannot run the event loop while another loop is running')

def run_forever(self):

"""Run until stop() is called."""

self._check_closed()

self._check_running()

self._set_coroutine_origin_tracking(self._debug)

self._thread_id = threading.get_ident()

old_agen_hooks = sys.get_asyncgen_hooks()

sys.set_asyncgen_hooks(firstiter=self._asyncgen_firstiter_hook,

finalizer=self._asyncgen_finalizer_hook)

try:

events._set_running_loop(self)

while True:

self._run_once()

if self._stopping:

break

finally:

self._stopping = False

self._thread_id = None

events._set_running_loop(None)

self._set_coroutine_origin_tracking(False)

sys.set_asyncgen_hooks(*old_agen_hooks)

def run_until_complete(self, future):

"""Run until the Future is done.

If the argument is a coroutine, it is wrapped in a Task.

WARNING: It would be disastrous to call run_until_complete()

with the same coroutine twice -- it would wrap it in two

different Tasks and that can't be good.

Return the Future's result, or raise its exception.

"""

self._check_closed()

self._check_running()

new_task = not futures.isfuture(future)

future = tasks.ensure_future(future, loop=self)

if new_task:

# An exception is raised if the future didn't complete, so there

# is no need to log the "destroy pending task" message

future._log_destroy_pending = False

future.add_done_callback(_run_until_complete_cb)

try:

self.run_forever()

except:

if new_task and future.done() and not future.cancelled():

# The coroutine raised a BaseException. Consume the exception

# to not log a warning, the caller doesn't have access to the

# local task.

future.exception()

raise

finally:

future.remove_done_callback(_run_until_complete_cb)

if not future.done():

raise RuntimeError('Event loop stopped before Future completed.')

return future.result()

def stop(self):

"""Stop running the event loop.

Every callback already scheduled will still run. This simply informs

run_forever to stop looping after a complete iteration.

"""

self._stopping = True

def close(self):

"""Close the event loop.

This clears the queues and shuts down the executor,

but does not wait for the executor to finish.

The event loop must not be running.

"""

if self.is_running():

raise RuntimeError("Cannot close a running event loop")

if self._closed:

return

if self._debug:

logger.debug("Close %r", self)

self._closed = True

self._ready.clear()

self._scheduled.clear()

executor = self._default_executor

if executor is not None:

self._default_executor = None

executor.shutdown(wait=False)

def is_closed(self):

"""Returns True if the event loop was closed."""

return self._closed

def __del__(self, _warn=warnings.warn):

if not self.is_closed():

_warn(f"unclosed event loop {self!r}", ResourceWarning, source=self)

if not self.is_running():

self.close()

def is_running(self):

"""Returns True if the event loop is running."""

return (self._thread_id is not None)

def time(self):

"""Return the time according to the event loop's clock.

This is a float expressed in seconds since an epoch, but the

epoch, precision, accuracy and drift are unspecified and may

differ per event loop.

"""

return time.monotonic()

def call_later(self, delay, callback, *args, context=None):

"""Arrange for a callback to be called at a given time.

Return a Handle: an opaque object with a cancel() method that

can be used to cancel the call.

The delay can be an int or float, expressed in seconds. It is

always relative to the current time.

Each callback will be called exactly once. If two callbacks

are scheduled for exactly the same time, it undefined which

will be called first.

Any positional arguments after the callback will be passed to

the callback when it is called.

"""

timer = self.call_at(self.time() + delay, callback, *args,

context=context)

if timer._source_traceback:

del timer._source_traceback[-1]

return timer

def call_at(self, when, callback, *args, context=None):

"""Like call_later(), but uses an absolute time.

Absolute time corresponds to the event loop's time() method.

"""

self._check_closed()

if self._debug:

self._check_thread()

self._check_callback(callback, 'call_at')

timer = events.TimerHandle(when, callback, args, self, context)

if timer._source_traceback:

del timer._source_traceback[-1]

heapq.heappush(self._scheduled, timer)

timer._scheduled = True

return timer

def call_soon(self, callback, *args, context=None):

"""Arrange for a callback to be called as soon as possible.

This operates as a FIFO queue: callbacks are called in the

order in which they are registered. Each callback will be

called exactly once.

Any positional arguments after the callback will be passed to

the callback when it is called.

"""

self._check_closed()

if self._debug:

self._check_thread()

self._check_callback(callback, 'call_soon')

handle = self._call_soon(callback, args, context)

if handle._source_traceback:

del handle._source_traceback[-1]

return handle

def _check_callback(self, callback, method):

if (coroutines.iscoroutine(callback) or

coroutines.iscoroutinefunction(callback)):

raise TypeError(

f"coroutines cannot be used with {method}()")

if not callable(callback):

raise TypeError(

f'a callable object was expected by {method}(), '

f'got {callback!r}')

def _call_soon(self, callback, args, context):

handle = events.Handle(callback, args, self, context)

if handle._source_traceback:

del handle._source_traceback[-1]

self._ready.append(handle)

return handle

def _check_thread(self):

"""Check that the current thread is the thread running the event loop.

Non-thread-safe methods of this class make this assumption and will

likely behave incorrectly when the assumption is violated.

Should only be called when (self._debug == True). The caller is

responsible for checking this condition for performance reasons.

"""

if self._thread_id is None:

return

thread_id = threading.get_ident()

if thread_id != self._thread_id:

raise RuntimeError(

"Non-thread-safe operation invoked on an event loop other "

"than the current one")

def call_soon_threadsafe(self, callback, *args, context=None):

"""Like call_soon(), but thread-safe."""

self._check_closed()

if self._debug:

self._check_callback(callback, 'call_soon_threadsafe')

handle = self._call_soon(callback, args, context)

if handle._source_traceback:

del handle._source_traceback[-1]

self._write_to_self()

return handle

def run_in_executor(self, executor, func, *args):

self._check_closed()

if self._debug:

self._check_callback(func, 'run_in_executor')

if executor is None:

executor = self._default_executor

if executor is None:

executor = concurrent.futures.ThreadPoolExecutor()

self._default_executor = executor

return futures.wrap_future(

executor.submit(func, *args), loop=self)

def set_default_executor(self, executor):

if not isinstance(executor, concurrent.futures.ThreadPoolExecutor):

warnings.warn(

'Using the default executor that is not an instance of '

'ThreadPoolExecutor is deprecated and will be prohibited '

'in Python 3.9',

DeprecationWarning, 2)

self._default_executor = executor

def _getaddrinfo_debug(self, host, port, family, type, proto, flags):

msg = [f"{host}:{port!r}"]

if family:

msg.append(f'family={family!r}')

if type:

msg.append(f'type={type!r}')

if proto:

msg.append(f'proto={proto!r}')

if flags:

msg.append(f'flags={flags!r}')

msg = ', '.join(msg)

logger.debug('Get address info %s', msg)

t0 = self.time()

addrinfo = socket.getaddrinfo(host, port, family, type, proto, flags)

dt = self.time() - t0

msg = f'Getting address info {msg} took {dt * 1e3:.3f}ms: {addrinfo!r}'

if dt >= self.slow_callback_duration:

logger.info(msg)

else:

logger.debug(msg)

return addrinfo

async def getaddrinfo(self, host, port, *,

family=0, type=0, proto=0, flags=0):

if self._debug:

getaddr_func = self._getaddrinfo_debug

else:

getaddr_func = socket.getaddrinfo

return await self.run_in_executor(

None, getaddr_func, host, port, family, type, proto, flags)

async def getnameinfo(self, sockaddr, flags=0):

return await self.run_in_executor(

None, socket.getnameinfo, sockaddr, flags)

async def sock_sendfile(self, sock, file, offset=0, count=None,

*, fallback=True):

if self._debug and sock.gettimeout() != 0:

raise ValueError("the socket must be non-blocking")

self._check_sendfile_params(sock, file, offset, count)

try:

return await self._sock_sendfile_native(sock, file,

offset, count)

except exceptions.SendfileNotAvailableError as exc:

if not fallback:

raise

return await self._sock_sendfile_fallback(sock, file,

offset, count)

async def _sock_sendfile_native(self, sock, file, offset, count):

# NB: sendfile syscall is not supported for SSL sockets and

# non-mmap files even if sendfile is supported by OS

raise exceptions.SendfileNotAvailableError(

f"syscall sendfile is not available for socket {sock!r} "

"and file {file!r} combination")

async def _sock_sendfile_fallback(self, sock, file, offset, count):

if offset:

file.seek(offset)

blocksize = (

min(count, constants.SENDFILE_FALLBACK_READBUFFER_SIZE)

if count else constants.SENDFILE_FALLBACK_READBUFFER_SIZE

)

buf = bytearray(blocksize)

total_sent = 0

try:

while True:

if count:

blocksize = min(count - total_sent, blocksize)

if blocksize <= 0:

break

view = memoryview(buf)[:blocksize]

read = await self.run_in_executor(None, file.readinto, view)

if not read:

break # EOF

await self.sock_sendall(sock, view[:read])

total_sent += read

return total_sent

finally:

if total_sent > 0 and hasattr(file, 'seek'):

file.seek(offset + total_sent)

def _check_sendfile_params(self, sock, file, offset, count):

if 'b' not in getattr(file, 'mode', 'b'):

raise ValueError("file should be opened in binary mode")

if not sock.type == socket.SOCK_STREAM:

raise ValueError("only SOCK_STREAM type sockets are supported")

if count is not None:

if not isinstance(count, int):

raise TypeError(

"count must be a positive integer (got {!r})".format(count))

if count <= 0:

raise ValueError(

"count must be a positive integer (got {!r})".format(count))

if not isinstance(offset, int):

raise TypeError(

"offset must be a non-negative integer (got {!r})".format(

offset))

if offset < 0:

raise ValueError(

"offset must be a non-negative integer (got {!r})".format(

offset))

async def _connect_sock(self, exceptions, addr_info, local_addr_infos=None):

"""Create, bind and connect one socket."""

my_exceptions = []

exceptions.append(my_exceptions)

family, type_, proto, _, address = addr_info

sock = None

try:

sock = socket.socket(family=family, type=type_, proto=proto)

sock.setblocking(False)

if local_addr_infos is not None:

for _, _, _, _, laddr in local_addr_infos:

try:

sock.bind(laddr)

break

except OSError as exc:

msg = (

f'error while attempting to bind on '

f'address {laddr!r}: '

f'{exc.strerror.lower()}'

)

exc = OSError(exc.errno, msg)

my_exceptions.append(exc)

else: # all bind attempts failed

raise my_exceptions.pop()

await self.sock_connect(sock, address)

return sock

except OSError as exc:

my_exceptions.append(exc)

if sock is not None:

sock.close()

raise

except:

if sock is not None:

sock.close()

raise

async def create_connection(

self, protocol_factory, host=None, port=None,

*, ssl=None, family=0,

proto=0, flags=0, sock=None,

local_addr=None, server_hostname=None,

ssl_handshake_timeout=None,

happy_eyeballs_delay=None, interleave=None):

"""Connect to a TCP server.

Create a streaming transport connection to a given Internet host and

port: socket family AF_INET or socket.AF_INET6 depending on host (or

family if specified), socket type SOCK_STREAM. protocol_factory must be

a callable returning a protocol instance.

This method is a coroutine which will try to establish the connection

in the background. When successful, the coroutine returns a

(transport, protocol) pair.

"""

if server_hostname is not None and not ssl:

raise ValueError('server_hostname is only meaningful with ssl')

if server_hostname is None and ssl:

# Use host as default for server_hostname. It is an error

# if host is empty or not set, e.g. when an

# already-connected socket was passed or when only a port

# is given. To avoid this error, you can pass

# server_hostname='' -- this will bypass the hostname

# check. (This also means that if host is a numeric

# IP/IPv6 address, we will attempt to verify that exact

# address; this will probably fail, but it is possible to

# create a certificate for a specific IP address, so we

# don't judge it here.)

if not host:

raise ValueError('You must set server_hostname '

'when using ssl without a host')

server_hostname = host

if ssl_handshake_timeout is not None and not ssl:

raise ValueError(

'ssl_handshake_timeout is only meaningful with ssl')

if happy_eyeballs_delay is not None and interleave is None:

# If using happy eyeballs, default to interleave addresses by family

interleave = 1

if host is not None or port is not None:

if sock is not None:

raise ValueError(

'host/port and sock can not be specified at the same time')

infos = await self._ensure_resolved(

(host, port), family=family,

type=socket.SOCK_STREAM, proto=proto, flags=flags, loop=self)

if not infos:

raise OSError('getaddrinfo() returned empty list')

if local_addr is not None:

laddr_infos = await self._ensure_resolved(

local_addr, family=family,

type=socket.SOCK_STREAM, proto=proto,

flags=flags, loop=self)

if not laddr_infos:

raise OSError('getaddrinfo() returned empty list')

else:

laddr_infos = None