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httppeer: remove support for connecting to <0.9.1 servers (BC)...
httppeer: remove support for connecting to <0.9.1 servers (BC) Previously, HTTP wire protocol clients would attempt a "capabilities" wire protocol command. If that failed, they would fall back to issuing a "between" command. The "capabilities" command was added in Mercurial 0.9.1 (released July 2006). The "between" command has been present for as long as the wire protocol has existed. So if the "between" command failed, it was safe to assume that the remote could not speak any version of the Mercurial wire protocol. The "between" fallback was added in 395a84f78736 in 2011. Before that changeset, Mercurial would *always* issue the "between" command and would issue "capabilities" if capabilities were requested. At that time, many connections would issue "capabilities" eventually, so it was decided to issue "capabilities" by default and fall back to "between" if that failed. This saved a round trip when connecting to modern servers while still preserving compatibility with legacy servers. Fast forward ~7 years. Mercurial servers supporting "capabilities" have been around for over a decade. If modern clients are connecting to <0.9.1 servers, they are getting a bad experience. They may even be getting bad data (an old server is vulnerable to numerous security issues and could have been p0wned, leading to a Mercurial repository serving backdoors or other badness). In addition, the fallback can harm experience for modern servers. If a client experiences an intermittent HTTP request failure (due to bad network, etc) and falls back to a "between" that works, it would assume an empty capability set and would attempt to communicate with the repository using a very ancient wire protocol. Auditing HTTP logs for hg.mozilla.org, I did find a handful of requests for the null range of the "between" command. However, requests can be days apart. And when I do see requests, they come in batches. Those batches seem to correlate to spikes of HTTP 500 or other server/network events. So I think these requests are fallbacks from failed "capabilities" requests and not from old clients. If you need even more evidence to discontinue support, apparently we have no test coverage for communicating with servers not supporting "capabilities." I know this because all tests pass with the "between" fallback removed. Finally, server-side support for <0.9.1 pushing (the "addchangegroup" wire protocol command along with locking-related commands) was dropped from the HTTP client in fda0867cfe03 in 2017 and the SSH client in 9f6e0e7ef828 in 2015. I think this all adds up to enough justification for removing client support for communicating with servers not supporting "capabilities." So this commit removes that fallback. Differential Revision: https://phab.mercurial-scm.org/D2001

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selectors2.py
743 lines | 26.8 KiB | text/x-python | PythonLexer
""" Back-ported, durable, and portable selectors """
# MIT License
#
# Copyright (c) 2017 Seth Michael Larson
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
from __future__ import absolute_import
import collections
import errno
import math
import select
import socket
import sys
import time
from .. import pycompat
namedtuple = collections.namedtuple
Mapping = collections.Mapping
try:
monotonic = time.monotonic
except AttributeError:
monotonic = time.time
__author__ = 'Seth Michael Larson'
__email__ = 'sethmichaellarson@protonmail.com'
__version__ = '2.0.0'
__license__ = 'MIT'
__url__ = 'https://www.github.com/SethMichaelLarson/selectors2'
__all__ = ['EVENT_READ',
'EVENT_WRITE',
'SelectorKey',
'DefaultSelector',
'BaseSelector']
EVENT_READ = (1 << 0)
EVENT_WRITE = (1 << 1)
_DEFAULT_SELECTOR = None
_SYSCALL_SENTINEL = object() # Sentinel in case a system call returns None.
_ERROR_TYPES = (OSError, IOError, socket.error)
SelectorKey = namedtuple('SelectorKey', ['fileobj', 'fd', 'events', 'data'])
class _SelectorMapping(Mapping):
""" Mapping of file objects to selector keys """
def __init__(self, selector):
self._selector = selector
def __len__(self):
return len(self._selector._fd_to_key)
def __getitem__(self, fileobj):
try:
fd = self._selector._fileobj_lookup(fileobj)
return self._selector._fd_to_key[fd]
except KeyError:
raise KeyError("{0!r} is not registered.".format(fileobj))
def __iter__(self):
return iter(self._selector._fd_to_key)
def _fileobj_to_fd(fileobj):
""" Return a file descriptor from a file object. If
given an integer will simply return that integer back. """
if isinstance(fileobj, int):
fd = fileobj
else:
try:
fd = int(fileobj.fileno())
except (AttributeError, TypeError, ValueError):
raise ValueError("Invalid file object: {0!r}".format(fileobj))
if fd < 0:
raise ValueError("Invalid file descriptor: {0}".format(fd))
return fd
class BaseSelector(object):
""" Abstract Selector class
A selector supports registering file objects to be monitored
for specific I/O events.
A file object is a file descriptor or any object with a
`fileno()` method. An arbitrary object can be attached to the
file object which can be used for example to store context info,
a callback, etc.
A selector can use various implementations (select(), poll(), epoll(),
and kqueue()) depending on the platform. The 'DefaultSelector' class uses
the most efficient implementation for the current platform.
"""
def __init__(self):
# Maps file descriptors to keys.
self._fd_to_key = {}
# Read-only mapping returned by get_map()
self._map = _SelectorMapping(self)
def _fileobj_lookup(self, fileobj):
""" Return a file descriptor from a file object.
This wraps _fileobj_to_fd() to do an exhaustive
search in case the object is invalid but we still
have it in our map. Used by unregister() so we can
unregister an object that was previously registered
even if it is closed. It is also used by _SelectorMapping
"""
try:
return _fileobj_to_fd(fileobj)
except ValueError:
# Search through all our mapped keys.
for key in self._fd_to_key.values():
if key.fileobj is fileobj:
return key.fd
# Raise ValueError after all.
raise
def register(self, fileobj, events, data=None):
""" Register a file object for a set of events to monitor. """
if (not events) or (events & ~(EVENT_READ | EVENT_WRITE)):
raise ValueError("Invalid events: {0!r}".format(events))
key = SelectorKey(fileobj, self._fileobj_lookup(fileobj), events, data)
if key.fd in self._fd_to_key:
raise KeyError("{0!r} (FD {1}) is already registered"
.format(fileobj, key.fd))
self._fd_to_key[key.fd] = key
return key
def unregister(self, fileobj):
""" Unregister a file object from being monitored. """
try:
key = self._fd_to_key.pop(self._fileobj_lookup(fileobj))
except KeyError:
raise KeyError("{0!r} is not registered".format(fileobj))
# Getting the fileno of a closed socket on Windows errors with EBADF.
except socket.error as err:
if err.errno != errno.EBADF:
raise
else:
for key in self._fd_to_key.values():
if key.fileobj is fileobj:
self._fd_to_key.pop(key.fd)
break
else:
raise KeyError("{0!r} is not registered".format(fileobj))
return key
def modify(self, fileobj, events, data=None):
""" Change a registered file object monitored events and data. """
# NOTE: Some subclasses optimize this operation even further.
try:
key = self._fd_to_key[self._fileobj_lookup(fileobj)]
except KeyError:
raise KeyError("{0!r} is not registered".format(fileobj))
if events != key.events:
self.unregister(fileobj)
key = self.register(fileobj, events, data)
elif data != key.data:
# Use a shortcut to update the data.
key = key._replace(data=data)
self._fd_to_key[key.fd] = key
return key
def select(self, timeout=None):
""" Perform the actual selection until some monitored file objects
are ready or the timeout expires. """
raise NotImplementedError()
def close(self):
""" Close the selector. This must be called to ensure that all
underlying resources are freed. """
self._fd_to_key.clear()
self._map = None
def get_key(self, fileobj):
""" Return the key associated with a registered file object. """
mapping = self.get_map()
if mapping is None:
raise RuntimeError("Selector is closed")
try:
return mapping[fileobj]
except KeyError:
raise KeyError("{0!r} is not registered".format(fileobj))
def get_map(self):
""" Return a mapping of file objects to selector keys """
return self._map
def _key_from_fd(self, fd):
""" Return the key associated to a given file descriptor
Return None if it is not found. """
try:
return self._fd_to_key[fd]
except KeyError:
return None
def __enter__(self):
return self
def __exit__(self, *_):
self.close()
# Almost all platforms have select.select()
if hasattr(select, "select"):
class SelectSelector(BaseSelector):
""" Select-based selector. """
def __init__(self):
super(SelectSelector, self).__init__()
self._readers = set()
self._writers = set()
def register(self, fileobj, events, data=None):
key = super(SelectSelector, self).register(fileobj, events, data)
if events & EVENT_READ:
self._readers.add(key.fd)
if events & EVENT_WRITE:
self._writers.add(key.fd)
return key
def unregister(self, fileobj):
key = super(SelectSelector, self).unregister(fileobj)
self._readers.discard(key.fd)
self._writers.discard(key.fd)
return key
def select(self, timeout=None):
# Selecting on empty lists on Windows errors out.
if not len(self._readers) and not len(self._writers):
return []
timeout = None if timeout is None else max(timeout, 0.0)
ready = []
r, w, _ = _syscall_wrapper(self._wrap_select, True, self._readers,
self._writers, timeout)
r = set(r)
w = set(w)
for fd in r | w:
events = 0
if fd in r:
events |= EVENT_READ
if fd in w:
events |= EVENT_WRITE
key = self._key_from_fd(fd)
if key:
ready.append((key, events & key.events))
return ready
def _wrap_select(self, r, w, timeout=None):
""" Wrapper for select.select because timeout is a positional arg """
return select.select(r, w, [], timeout)
__all__.append('SelectSelector')
# Jython has a different implementation of .fileno() for socket objects.
if pycompat.isjython:
class _JythonSelectorMapping(object):
""" This is an implementation of _SelectorMapping that is built
for use specifically with Jython, which does not provide a hashable
value from socket.socket.fileno(). """
def __init__(self, selector):
assert isinstance(selector, JythonSelectSelector)
self._selector = selector
def __len__(self):
return len(self._selector._sockets)
def __getitem__(self, fileobj):
for sock, key in self._selector._sockets:
if sock is fileobj:
return key
else:
raise KeyError("{0!r} is not registered.".format(fileobj))
class JythonSelectSelector(SelectSelector):
""" This is an implementation of SelectSelector that is for Jython
which works around that Jython's socket.socket.fileno() does not
return an integer fd value. All SelectorKey.fd will be equal to -1
and should not be used. This instead uses object id to compare fileobj
and will only use select.select as it's the only selector that allows
directly passing in socket objects rather than registering fds.
See: http://bugs.jython.org/issue1678
https://wiki.python.org/jython/NewSocketModule#socket.fileno.28.29_does_not_return_an_integer
"""
def __init__(self):
super(JythonSelectSelector, self).__init__()
self._sockets = [] # Uses a list of tuples instead of dictionary.
self._map = _JythonSelectorMapping(self)
self._readers = []
self._writers = []
# Jython has a select.cpython_compatible_select function in older versions.
self._select_func = getattr(select, 'cpython_compatible_select', select.select)
def register(self, fileobj, events, data=None):
for sock, _ in self._sockets:
if sock is fileobj:
raise KeyError("{0!r} is already registered"
.format(fileobj, sock))
key = SelectorKey(fileobj, -1, events, data)
self._sockets.append((fileobj, key))
if events & EVENT_READ:
self._readers.append(fileobj)
if events & EVENT_WRITE:
self._writers.append(fileobj)
return key
def unregister(self, fileobj):
for i, (sock, key) in enumerate(self._sockets):
if sock is fileobj:
break
else:
raise KeyError("{0!r} is not registered.".format(fileobj))
if key.events & EVENT_READ:
self._readers.remove(fileobj)
if key.events & EVENT_WRITE:
self._writers.remove(fileobj)
del self._sockets[i]
return key
def _wrap_select(self, r, w, timeout=None):
""" Wrapper for select.select because timeout is a positional arg """
return self._select_func(r, w, [], timeout)
__all__.append('JythonSelectSelector')
SelectSelector = JythonSelectSelector # Override so the wrong selector isn't used.
if hasattr(select, "poll"):
class PollSelector(BaseSelector):
""" Poll-based selector """
def __init__(self):
super(PollSelector, self).__init__()
self._poll = select.poll()
def register(self, fileobj, events, data=None):
key = super(PollSelector, self).register(fileobj, events, data)
event_mask = 0
if events & EVENT_READ:
event_mask |= select.POLLIN
if events & EVENT_WRITE:
event_mask |= select.POLLOUT
self._poll.register(key.fd, event_mask)
return key
def unregister(self, fileobj):
key = super(PollSelector, self).unregister(fileobj)
self._poll.unregister(key.fd)
return key
def _wrap_poll(self, timeout=None):
""" Wrapper function for select.poll.poll() so that
_syscall_wrapper can work with only seconds. """
if timeout is not None:
if timeout <= 0:
timeout = 0
else:
# select.poll.poll() has a resolution of 1 millisecond,
# round away from zero to wait *at least* timeout seconds.
timeout = math.ceil(timeout * 1000)
result = self._poll.poll(timeout)
return result
def select(self, timeout=None):
ready = []
fd_events = _syscall_wrapper(self._wrap_poll, True, timeout=timeout)
for fd, event_mask in fd_events:
events = 0
if event_mask & ~select.POLLIN:
events |= EVENT_WRITE
if event_mask & ~select.POLLOUT:
events |= EVENT_READ
key = self._key_from_fd(fd)
if key:
ready.append((key, events & key.events))
return ready
__all__.append('PollSelector')
if hasattr(select, "epoll"):
class EpollSelector(BaseSelector):
""" Epoll-based selector """
def __init__(self):
super(EpollSelector, self).__init__()
self._epoll = select.epoll()
def fileno(self):
return self._epoll.fileno()
def register(self, fileobj, events, data=None):
key = super(EpollSelector, self).register(fileobj, events, data)
events_mask = 0
if events & EVENT_READ:
events_mask |= select.EPOLLIN
if events & EVENT_WRITE:
events_mask |= select.EPOLLOUT
_syscall_wrapper(self._epoll.register, False, key.fd, events_mask)
return key
def unregister(self, fileobj):
key = super(EpollSelector, self).unregister(fileobj)
try:
_syscall_wrapper(self._epoll.unregister, False, key.fd)
except _ERROR_TYPES:
# This can occur when the fd was closed since registry.
pass
return key
def select(self, timeout=None):
if timeout is not None:
if timeout <= 0:
timeout = 0.0
else:
# select.epoll.poll() has a resolution of 1 millisecond
# but luckily takes seconds so we don't need a wrapper
# like PollSelector. Just for better rounding.
timeout = math.ceil(timeout * 1000) * 0.001
timeout = float(timeout)
else:
timeout = -1.0 # epoll.poll() must have a float.
# We always want at least 1 to ensure that select can be called
# with no file descriptors registered. Otherwise will fail.
max_events = max(len(self._fd_to_key), 1)
ready = []
fd_events = _syscall_wrapper(self._epoll.poll, True,
timeout=timeout,
maxevents=max_events)
for fd, event_mask in fd_events:
events = 0
if event_mask & ~select.EPOLLIN:
events |= EVENT_WRITE
if event_mask & ~select.EPOLLOUT:
events |= EVENT_READ
key = self._key_from_fd(fd)
if key:
ready.append((key, events & key.events))
return ready
def close(self):
self._epoll.close()
super(EpollSelector, self).close()
__all__.append('EpollSelector')
if hasattr(select, "devpoll"):
class DevpollSelector(BaseSelector):
"""Solaris /dev/poll selector."""
def __init__(self):
super(DevpollSelector, self).__init__()
self._devpoll = select.devpoll()
def fileno(self):
return self._devpoll.fileno()
def register(self, fileobj, events, data=None):
key = super(DevpollSelector, self).register(fileobj, events, data)
poll_events = 0
if events & EVENT_READ:
poll_events |= select.POLLIN
if events & EVENT_WRITE:
poll_events |= select.POLLOUT
self._devpoll.register(key.fd, poll_events)
return key
def unregister(self, fileobj):
key = super(DevpollSelector, self).unregister(fileobj)
self._devpoll.unregister(key.fd)
return key
def _wrap_poll(self, timeout=None):
""" Wrapper function for select.poll.poll() so that
_syscall_wrapper can work with only seconds. """
if timeout is not None:
if timeout <= 0:
timeout = 0
else:
# select.devpoll.poll() has a resolution of 1 millisecond,
# round away from zero to wait *at least* timeout seconds.
timeout = math.ceil(timeout * 1000)
result = self._devpoll.poll(timeout)
return result
def select(self, timeout=None):
ready = []
fd_events = _syscall_wrapper(self._wrap_poll, True, timeout=timeout)
for fd, event_mask in fd_events:
events = 0
if event_mask & ~select.POLLIN:
events |= EVENT_WRITE
if event_mask & ~select.POLLOUT:
events |= EVENT_READ
key = self._key_from_fd(fd)
if key:
ready.append((key, events & key.events))
return ready
def close(self):
self._devpoll.close()
super(DevpollSelector, self).close()
__all__.append('DevpollSelector')
if hasattr(select, "kqueue"):
class KqueueSelector(BaseSelector):
""" Kqueue / Kevent-based selector """
def __init__(self):
super(KqueueSelector, self).__init__()
self._kqueue = select.kqueue()
def fileno(self):
return self._kqueue.fileno()
def register(self, fileobj, events, data=None):
key = super(KqueueSelector, self).register(fileobj, events, data)
if events & EVENT_READ:
kevent = select.kevent(key.fd,
select.KQ_FILTER_READ,
select.KQ_EV_ADD)
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
if events & EVENT_WRITE:
kevent = select.kevent(key.fd,
select.KQ_FILTER_WRITE,
select.KQ_EV_ADD)
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
return key
def unregister(self, fileobj):
key = super(KqueueSelector, self).unregister(fileobj)
if key.events & EVENT_READ:
kevent = select.kevent(key.fd,
select.KQ_FILTER_READ,
select.KQ_EV_DELETE)
try:
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
except _ERROR_TYPES:
pass
if key.events & EVENT_WRITE:
kevent = select.kevent(key.fd,
select.KQ_FILTER_WRITE,
select.KQ_EV_DELETE)
try:
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
except _ERROR_TYPES:
pass
return key
def select(self, timeout=None):
if timeout is not None:
timeout = max(timeout, 0)
max_events = len(self._fd_to_key) * 2
ready_fds = {}
kevent_list = _syscall_wrapper(self._kqueue.control, True,
None, max_events, timeout)
for kevent in kevent_list:
fd = kevent.ident
event_mask = kevent.filter
events = 0
if event_mask == select.KQ_FILTER_READ:
events |= EVENT_READ
if event_mask == select.KQ_FILTER_WRITE:
events |= EVENT_WRITE
key = self._key_from_fd(fd)
if key:
if key.fd not in ready_fds:
ready_fds[key.fd] = (key, events & key.events)
else:
old_events = ready_fds[key.fd][1]
ready_fds[key.fd] = (key, (events | old_events) & key.events)
return list(ready_fds.values())
def close(self):
self._kqueue.close()
super(KqueueSelector, self).close()
__all__.append('KqueueSelector')
def _can_allocate(struct):
""" Checks that select structs can be allocated by the underlying
operating system, not just advertised by the select module. We don't
check select() because we'll be hopeful that most platforms that
don't have it available will not advertise it. (ie: GAE) """
try:
# select.poll() objects won't fail until used.
if struct == 'poll':
p = select.poll()
p.poll(0)
# All others will fail on allocation.
else:
getattr(select, struct)().close()
return True
except (OSError, AttributeError):
return False
# Python 3.5 uses a more direct route to wrap system calls to increase speed.
if sys.version_info >= (3, 5):
def _syscall_wrapper(func, _, *args, **kwargs):
""" This is the short-circuit version of the below logic
because in Python 3.5+ all selectors restart system calls. """
return func(*args, **kwargs)
else:
def _syscall_wrapper(func, recalc_timeout, *args, **kwargs):
""" Wrapper function for syscalls that could fail due to EINTR.
All functions should be retried if there is time left in the timeout
in accordance with PEP 475. """
timeout = kwargs.get("timeout", None)
if timeout is None:
expires = None
recalc_timeout = False
else:
timeout = float(timeout)
if timeout < 0.0: # Timeout less than 0 treated as no timeout.
expires = None
else:
expires = monotonic() + timeout
args = list(args)
if recalc_timeout and "timeout" not in kwargs:
raise ValueError(
"Timeout must be in args or kwargs to be recalculated")
result = _SYSCALL_SENTINEL
while result is _SYSCALL_SENTINEL:
try:
result = func(*args, **kwargs)
# OSError is thrown by select.select
# IOError is thrown by select.epoll.poll
# select.error is thrown by select.poll.poll
# Aren't we thankful for Python 3.x rework for exceptions?
except (OSError, IOError, select.error) as e:
# select.error wasn't a subclass of OSError in the past.
errcode = None
if hasattr(e, "errno"):
errcode = e.errno
elif hasattr(e, "args"):
errcode = e.args[0]
# Also test for the Windows equivalent of EINTR.
is_interrupt = (errcode == errno.EINTR or (hasattr(errno, "WSAEINTR") and
errcode == errno.WSAEINTR))
if is_interrupt:
if expires is not None:
current_time = monotonic()
if current_time > expires:
raise OSError(errno=errno.ETIMEDOUT)
if recalc_timeout:
if "timeout" in kwargs:
kwargs["timeout"] = expires - current_time
continue
raise
return result
# Choose the best implementation, roughly:
# kqueue == devpoll == epoll > poll > select
# select() also can't accept a FD > FD_SETSIZE (usually around 1024)
def DefaultSelector():
""" This function serves as a first call for DefaultSelector to
detect if the select module is being monkey-patched incorrectly
by eventlet, greenlet, and preserve proper behavior. """
global _DEFAULT_SELECTOR
if _DEFAULT_SELECTOR is None:
if pycompat.isjython:
_DEFAULT_SELECTOR = JythonSelectSelector
elif _can_allocate('kqueue'):
_DEFAULT_SELECTOR = KqueueSelector
elif _can_allocate('devpoll'):
_DEFAULT_SELECTOR = DevpollSelector
elif _can_allocate('epoll'):
_DEFAULT_SELECTOR = EpollSelector
elif _can_allocate('poll'):
_DEFAULT_SELECTOR = PollSelector
elif hasattr(select, 'select'):
_DEFAULT_SELECTOR = SelectSelector
else: # Platform-specific: AppEngine
raise RuntimeError('Platform does not have a selector.')
return _DEFAULT_SELECTOR()