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Skip getaddrinfo if host is already resolved.

getaddrinfo takes an exclusive lock on some platforms, causing clients to queue
up waiting for the lock if many names are being resolved concurrently. Users
may want to handle name resolution in their own code, for the sake of caching,
using an alternate resolver, or to measure DNS duration separately from
connection duration. Skip getaddrinfo if the "host" passed into
create_connection is already resolved.
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ajdavis committed Dec 9, 2015
1 parent 74f2d8c commit 39c135baf73762830148236da622787052efba19
@@ -16,8 +16,10 @@
import collections
import concurrent.futures
import functools
import heapq
import inspect
import ipaddress
import itertools
import logging
import os
@@ -70,49 +72,83 @@ def _format_pipe(fd):
return repr(fd)
# Linux's sock.type is a bitmask that can include extra info about socket.
_SOCKET_TYPE_MASK = 0
if hasattr(socket, 'SOCK_NONBLOCK'):
_SOCKET_TYPE_MASK |= socket.SOCK_NONBLOCK
if hasattr(socket, 'SOCK_CLOEXEC'):
_SOCKET_TYPE_MASK |= socket.SOCK_CLOEXEC
@functools.lru_cache(maxsize=1024)
def _ipaddr_info(host, port, family, type, proto):
# Try to skip getaddrinfo if "host" is already an IP. Since getaddrinfo
# blocks on an exclusive lock on some platforms, users might handle name
# resolution in their own code and pass in resolved IPs.
if proto not in {0, socket.IPPROTO_TCP, socket.IPPROTO_UDP} or host is None:
return None
type &= ~_SOCKET_TYPE_MASK
if type == socket.SOCK_STREAM:
proto = socket.IPPROTO_TCP
elif type == socket.SOCK_DGRAM:
proto = socket.IPPROTO_UDP
else:
return None
if hasattr(socket, 'inet_pton'):
if family == socket.AF_UNSPEC:
afs = [socket.AF_INET, socket.AF_INET6]
else:
afs = [family]
for af in afs:
# Linux's inet_pton doesn't accept an IPv6 zone index after host,
# like '::1%lo0', so strip it. If we happen to make an invalid
# address look valid, we fail later in sock.connect or sock.bind.
try:
if af == socket.AF_INET6:
socket.inet_pton(af, host.partition('%')[0])
else:
socket.inet_pton(af, host)
return af, type, proto, '', (host, port)
except OSError:
pass
# "host" is not an IP address.
return None
# No inet_pton. (On Windows it's only available since Python 3.4.)
# Even though getaddrinfo with AI_NUMERICHOST would be non-blocking, it
# still requires a lock on some platforms, and waiting for that lock could
# block the event loop. Use ipaddress instead, it's just text parsing.
try:
addr = ipaddress.IPv4Address(host)
except ValueError:
try:
addr = ipaddress.IPv6Address(host.partition('%')[0])
except ValueError:
return None
af = socket.AF_INET if addr.version == 4 else socket.AF_INET6
if family not in (socket.AF_UNSPEC, af):
# "host" is wrong IP version for "family".
return None
return af, type, proto, '', (host, port)
def _check_resolved_address(sock, address):
# Ensure that the address is already resolved to avoid the trap of hanging
# the entire event loop when the address requires doing a DNS lookup.
#
# getaddrinfo() is slow (around 10 us per call): this function should only
# be called in debug mode
family = sock.family
if family == socket.AF_INET:
host, port = address
elif family == socket.AF_INET6:
host, port = address[:2]
else:
if hasattr(socket, 'AF_UNIX') and sock.family == socket.AF_UNIX:
return
# On Windows, socket.inet_pton() is only available since Python 3.4
if hasattr(socket, 'inet_pton'):
# getaddrinfo() is slow and has known issue: prefer inet_pton()
# if available
try:
socket.inet_pton(family, host)
except OSError as exc:
raise ValueError("address must be resolved (IP address), "
"got host %r: %s"
% (host, exc))
else:
# Use getaddrinfo(flags=AI_NUMERICHOST) to ensure that the address is
# already resolved.
type_mask = 0
if hasattr(socket, 'SOCK_NONBLOCK'):
type_mask |= socket.SOCK_NONBLOCK
if hasattr(socket, 'SOCK_CLOEXEC'):
type_mask |= socket.SOCK_CLOEXEC
try:
socket.getaddrinfo(host, port,
family=family,
type=(sock.type & ~type_mask),
proto=sock.proto,
flags=socket.AI_NUMERICHOST)
except socket.gaierror as err:
raise ValueError("address must be resolved (IP address), "
"got host %r: %s"
% (host, err))
host, port = address[:2]
if _ipaddr_info(host, port, sock.family, sock.type, sock.proto) is None:
raise ValueError("address must be resolved (IP address),"
" got host %r" % host)
def _run_until_complete_cb(fut):
@@ -535,7 +571,12 @@ def _getaddrinfo_debug(self, host, port, family, type, proto, flags):
def getaddrinfo(self, host, port, *,
family=0, type=0, proto=0, flags=0):
if self._debug:
info = _ipaddr_info(host, port, family, type, proto)
if info is not None:
fut = futures.Future(loop=self)
fut.set_result([info])
return fut
elif self._debug:
return self.run_in_executor(None, self._getaddrinfo_debug,
host, port, family, type, proto, flags)
else:
@@ -441,8 +441,7 @@ def sock_sendall(self, sock, data):
def sock_connect(self, sock, address):
try:
if self._debug:
base_events._check_resolved_address(sock, address)
base_events._check_resolved_address(sock, address)
except ValueError as err:
fut = futures.Future(loop=self)
fut.set_exception(err)
@@ -397,8 +397,7 @@ def sock_connect(self, sock, address):
raise ValueError("the socket must be non-blocking")
fut = futures.Future(loop=self)
try:
if self._debug:
base_events._check_resolved_address(sock, address)
base_events._check_resolved_address(sock, address)
except ValueError as err:
fut.set_exception(err)
else:
@@ -446,9 +446,14 @@ def disable_logger():
finally:
logger.setLevel(old_level)
def mock_nonblocking_socket():
def mock_nonblocking_socket(proto=socket.IPPROTO_TCP, type=socket.SOCK_STREAM,
family=socket.AF_INET):
"""Create a mock of a non-blocking socket."""
sock = mock.Mock(socket.socket)
sock = mock.MagicMock(socket.socket)
sock.proto = proto
sock.type = type
sock.family = family
sock.gettimeout.return_value = 0.0
return sock
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