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"""Base implementation."""
import asyncio
import collections
import contextlib
import functools
import itertools
import socket
from typing import List, Optional, Sequence, Set, Union
from . import _staggered
from .types import AddrInfoType, SocketFactoryType
async def start_connection(
addr_infos: Sequence[AddrInfoType],
*,
local_addr_infos: Optional[Sequence[AddrInfoType]] = None,
happy_eyeballs_delay: Optional[float] = None,
interleave: Optional[int] = None,
loop: Optional[asyncio.AbstractEventLoop] = None,
socket_factory: Optional[SocketFactoryType] = None,
) -> socket.socket:
"""
Connect to a TCP server.
Create a socket connection to a specified destination. The
destination is specified as a list of AddrInfoType tuples as
returned from getaddrinfo().
The arguments are, in order:
* ``family``: the address family, e.g. ``socket.AF_INET`` or
``socket.AF_INET6``.
* ``type``: the socket type, e.g. ``socket.SOCK_STREAM`` or
``socket.SOCK_DGRAM``.
* ``proto``: the protocol, e.g. ``socket.IPPROTO_TCP`` or
``socket.IPPROTO_UDP``.
* ``canonname``: the canonical name of the address, e.g.
``"www.python.org"``.
* ``sockaddr``: the socket address
This method is a coroutine which will try to establish the connection
in the background. When successful, the coroutine returns a
socket.
The expected use case is to use this method in conjunction with
loop.create_connection() to establish a connection to a server::
socket = await start_connection(addr_infos)
transport, protocol = await loop.create_connection(
MyProtocol, sock=socket, ...)
"""
if not (current_loop := loop):
current_loop = asyncio.get_running_loop()
single_addr_info = len(addr_infos) == 1
if happy_eyeballs_delay is not None and interleave is None:
# If using happy eyeballs, default to interleave addresses by family
interleave = 1
if interleave and not single_addr_info:
addr_infos = _interleave_addrinfos(addr_infos, interleave)
sock: Optional[socket.socket] = None
# uvloop can raise RuntimeError instead of OSError
exceptions: List[List[Union[OSError, RuntimeError]]] = []
if happy_eyeballs_delay is None or single_addr_info:
# not using happy eyeballs
for addrinfo in addr_infos:
try:
sock = await _connect_sock(
current_loop,
exceptions,
addrinfo,
local_addr_infos,
None,
socket_factory,
)
break
except (RuntimeError, OSError):
continue
else: # using happy eyeballs
open_sockets: Set[socket.socket] = set()
try:
sock, _, _ = await _staggered.staggered_race(
(
functools.partial(
_connect_sock,
current_loop,
exceptions,
addrinfo,
local_addr_infos,
open_sockets,
socket_factory,
)
for addrinfo in addr_infos
),
happy_eyeballs_delay,
)
finally:
# If we have a winner, staggered_race will
# cancel the other tasks, however there is a
# small race window where any of the other tasks
# can be done before they are cancelled which
# will leave the socket open. To avoid this problem
# we pass a set to _connect_sock to keep track of
# the open sockets and close them here if there
# are any "runner up" sockets.
for s in open_sockets:
if s is not sock:
with contextlib.suppress(OSError):
s.close()
open_sockets = None # type: ignore[assignment]
if sock is None:
all_exceptions = [exc for sub in exceptions for exc in sub]
try:
first_exception = all_exceptions[0]
if len(all_exceptions) == 1:
raise first_exception
else:
# If they all have the same str(), raise one.
model = str(first_exception)
if all(str(exc) == model for exc in all_exceptions):
raise first_exception
# Raise a combined exception so the user can see all
# the various error messages.
msg = "Multiple exceptions: {}".format(
", ".join(str(exc) for exc in all_exceptions)
)
# If the errno is the same for all exceptions, raise
# an OSError with that errno.
if isinstance(first_exception, OSError):
first_errno = first_exception.errno
if all(
isinstance(exc, OSError) and exc.errno == first_errno
for exc in all_exceptions
):
raise OSError(first_errno, msg)
elif isinstance(first_exception, RuntimeError) and all(
isinstance(exc, RuntimeError) for exc in all_exceptions
):
raise RuntimeError(msg)
# We have a mix of OSError and RuntimeError
# so we have to pick which one to raise.
# and we raise OSError for compatibility
raise OSError(msg)
finally:
all_exceptions = None # type: ignore[assignment]
exceptions = None # type: ignore[assignment]
return sock
async def _connect_sock(
loop: asyncio.AbstractEventLoop,
exceptions: List[List[Union[OSError, RuntimeError]]],
addr_info: AddrInfoType,
local_addr_infos: Optional[Sequence[AddrInfoType]] = None,
open_sockets: Optional[Set[socket.socket]] = None,
socket_factory: Optional[SocketFactoryType] = None,
) -> socket.socket:
"""
Create, bind and connect one socket.
If open_sockets is passed, add the socket to the set of open sockets.
Any failure caught here will remove the socket from the set and close it.
Callers can use this set to close any sockets that are not the winner
of all staggered tasks in the result there are runner up sockets aka
multiple winners.
"""
my_exceptions: List[Union[OSError, RuntimeError]] = []
exceptions.append(my_exceptions)
family, type_, proto, _, address = addr_info
sock = None
try:
if socket_factory is not None:
sock = socket_factory(addr_info)
else:
sock = socket.socket(family=family, type=type_, proto=proto)
if open_sockets is not None:
open_sockets.add(sock)
sock.setblocking(False)
if local_addr_infos is not None:
for lfamily, _, _, _, laddr in local_addr_infos:
# skip local addresses of different family
if lfamily != family:
continue
try:
sock.bind(laddr)
break
except OSError as exc:
msg = (
f"error while attempting to bind on "
f"address {laddr!r}: "
f"{(exc.strerror or '').lower()}"
)
exc = OSError(exc.errno, msg)
my_exceptions.append(exc)
else: # all bind attempts failed
if my_exceptions:
raise my_exceptions.pop()
else:
raise OSError(f"no matching local address with {family=} found")
await loop.sock_connect(sock, address)
return sock
except (RuntimeError, OSError) as exc:
my_exceptions.append(exc)
if sock is not None:
if open_sockets is not None:
open_sockets.remove(sock)
try:
sock.close()
except OSError as e:
my_exceptions.append(e)
raise
raise
except:
if sock is not None:
if open_sockets is not None:
open_sockets.remove(sock)
try:
sock.close()
except OSError as e:
my_exceptions.append(e)
raise
raise
finally:
exceptions = my_exceptions = None # type: ignore[assignment]
def _interleave_addrinfos(
addrinfos: Sequence[AddrInfoType], first_address_family_count: int = 1
) -> List[AddrInfoType]:
"""Interleave list of addrinfo tuples by family."""
# Group addresses by family
addrinfos_by_family: collections.OrderedDict[int, List[AddrInfoType]] = (
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: List[AddrInfoType] = []
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
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