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from __future__ import annotations
import contextlib
import logging
import random
import socket
import struct
import threading
import time
import uuid
from collections.abc import Iterable, Iterator, Mapping
from types import TracebackType
from typing import Any, Literal, overload
from ..exceptions import (
ConcurrencyError,
ConnectionClosed,
ConnectionClosedOK,
ProtocolError,
)
from ..frames import DATA_OPCODES, BytesLike, CloseCode, Frame, Opcode
from ..http11 import Request, Response
from ..protocol import CLOSED, OPEN, Event, Protocol, State
from ..typing import Data, LoggerLike, Subprotocol
from .messages import Assembler
from .utils import Deadline
__all__ = ["Connection"]
class Connection:
"""
:mod:`threading` implementation of a WebSocket connection.
:class:`Connection` provides APIs shared between WebSocket servers and
clients.
You shouldn't use it directly. Instead, use
:class:`~websockets.sync.client.ClientConnection` or
:class:`~websockets.sync.server.ServerConnection`.
"""
recv_bufsize = 65536
def __init__(
self,
socket: socket.socket,
protocol: Protocol,
*,
ping_interval: float | None = 20,
ping_timeout: float | None = 20,
close_timeout: float | None = 10,
max_queue: int | None | tuple[int | None, int | None] = 16,
) -> None:
self.socket = socket
self.protocol = protocol
self.ping_interval = ping_interval
self.ping_timeout = ping_timeout
self.close_timeout = close_timeout
if isinstance(max_queue, int) or max_queue is None:
max_queue = (max_queue, None)
self.max_queue = max_queue
# Inject reference to this instance in the protocol's logger.
self.protocol.logger = logging.LoggerAdapter(
self.protocol.logger,
{"websocket": self},
)
# Copy attributes from the protocol for convenience.
self.id: uuid.UUID = self.protocol.id
"""Unique identifier of the connection. Useful in logs."""
self.logger: LoggerLike = self.protocol.logger
"""Logger for this connection."""
self.debug = self.protocol.debug
# HTTP handshake request and response.
self.request: Request | None = None
"""Opening handshake request."""
self.response: Response | None = None
"""Opening handshake response."""
# Mutex serializing interactions with the protocol.
self.protocol_mutex = threading.Lock()
# Lock stopping reads when the assembler buffer is full.
self.recv_flow_control = threading.Lock()
# Assembler turning frames into messages and serializing reads.
self.recv_messages = Assembler(
*self.max_queue,
pause=self.recv_flow_control.acquire,
resume=self.recv_flow_control.release,
)
# Deadline for the closing handshake.
self.close_deadline: Deadline | None = None
# Whether we are busy sending a fragmented message.
self.send_in_progress = False
# Mapping of ping IDs to pong waiters, in chronological order.
self.pong_waiters: dict[bytes, tuple[threading.Event, float, bool]] = {}
self.latency: float = 0
"""
Latency of the connection, in seconds.
Latency is defined as the round-trip time of the connection. It is
measured by sending a Ping frame and waiting for a matching Pong frame.
Before the first measurement, :attr:`latency` is ``0``.
By default, websockets enables a :ref:`keepalive <keepalive>` mechanism
that sends Ping frames automatically at regular intervals. You can also
send Ping frames and measure latency with :meth:`ping`.
"""
# Thread that sends keepalive pings. None when ping_interval is None.
self.keepalive_thread: threading.Thread | None = None
# Exception raised in recv_events, to be chained to ConnectionClosed
# in the user thread in order to show why the TCP connection dropped.
self.recv_exc: BaseException | None = None
# Receiving events from the socket. This thread is marked as daemon to
# allow creating a connection in a non-daemon thread and using it in a
# daemon thread. This mustn't prevent the interpreter from exiting.
self.recv_events_thread = threading.Thread(
target=self.recv_events,
daemon=True,
)
# Start recv_events only after all attributes are initialized.
self.recv_events_thread.start()
# Public attributes
@property
def local_address(self) -> Any:
"""
Local address of the connection.
For IPv4 connections, this is a ``(host, port)`` tuple.
The format of the address depends on the address family.
See :meth:`~socket.socket.getsockname`.
"""
return self.socket.getsockname()
@property
def remote_address(self) -> Any:
"""
Remote address of the connection.
For IPv4 connections, this is a ``(host, port)`` tuple.
The format of the address depends on the address family.
See :meth:`~socket.socket.getpeername`.
"""
return self.socket.getpeername()
@property
def state(self) -> State:
"""
State of the WebSocket connection, defined in :rfc:`6455`.
This attribute is provided for completeness. Typical applications
shouldn't check its value. Instead, they should call :meth:`~recv` or
:meth:`send` and handle :exc:`~websockets.exceptions.ConnectionClosed`
exceptions.
"""
return self.protocol.state
@property
def subprotocol(self) -> Subprotocol | None:
"""
Subprotocol negotiated during the opening handshake.
:obj:`None` if no subprotocol was negotiated.
"""
return self.protocol.subprotocol
@property
def close_code(self) -> int | None:
"""
State of the WebSocket connection, defined in :rfc:`6455`.
This attribute is provided for completeness. Typical applications
shouldn't check its value. Instead, they should inspect attributes
of :exc:`~websockets.exceptions.ConnectionClosed` exceptions.
"""
return self.protocol.close_code
@property
def close_reason(self) -> str | None:
"""
State of the WebSocket connection, defined in :rfc:`6455`.
This attribute is provided for completeness. Typical applications
shouldn't check its value. Instead, they should inspect attributes
of :exc:`~websockets.exceptions.ConnectionClosed` exceptions.
"""
return self.protocol.close_reason
# Public methods
def __enter__(self) -> Connection:
return self
def __exit__(
self,
exc_type: type[BaseException] | None,
exc_value: BaseException | None,
traceback: TracebackType | None,
) -> None:
if exc_type is None:
self.close()
else:
self.close(CloseCode.INTERNAL_ERROR)
def __iter__(self) -> Iterator[Data]:
"""
Iterate on incoming messages.
The iterator calls :meth:`recv` and yields messages in an infinite loop.
It exits when the connection is closed normally. It raises a
:exc:`~websockets.exceptions.ConnectionClosedError` exception after a
protocol error or a network failure.
"""
try:
while True:
yield self.recv()
except ConnectionClosedOK:
return
# This overload structure is required to avoid the error:
# "parameter without a default follows parameter with a default"
@overload
def recv(self, timeout: float | None, decode: Literal[True]) -> str: ...
@overload
def recv(self, timeout: float | None, decode: Literal[False]) -> bytes: ...
@overload
def recv(self, timeout: float | None = None, *, decode: Literal[True]) -> str: ...
@overload
def recv(
self, timeout: float | None = None, *, decode: Literal[False]
) -> bytes: ...
@overload
def recv(
self, timeout: float | None = None, decode: bool | None = None
) -> Data: ...
def recv(self, timeout: float | None = None, decode: bool | None = None) -> Data:
"""
Receive the next message.
When the connection is closed, :meth:`recv` raises
:exc:`~websockets.exceptions.ConnectionClosed`. Specifically, it raises
:exc:`~websockets.exceptions.ConnectionClosedOK` after a normal closure
and :exc:`~websockets.exceptions.ConnectionClosedError` after a protocol
error or a network failure. This is how you detect the end of the
message stream.
If ``timeout`` is :obj:`None`, block until a message is received. If
``timeout`` is set, wait up to ``timeout`` seconds for a message to be
received and return it, else raise :exc:`TimeoutError`. If ``timeout``
is ``0`` or negative, check if a message has been received already and
return it, else raise :exc:`TimeoutError`.
If the message is fragmented, wait until all fragments are received,
reassemble them, and return the whole message.
Args:
timeout: Timeout for receiving a message in seconds.
decode: Set this flag to override the default behavior of returning
:class:`str` or :class:`bytes`. See below for details.
Returns:
A string (:class:`str`) for a Text_ frame or a bytestring
(:class:`bytes`) for a Binary_ frame.
.. _Text: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
.. _Binary: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
You may override this behavior with the ``decode`` argument:
* Set ``decode=False`` to disable UTF-8 decoding of Text_ frames and
return a bytestring (:class:`bytes`). This improves performance
when decoding isn't needed, for example if the message contains
JSON and you're using a JSON library that expects a bytestring.
* Set ``decode=True`` to force UTF-8 decoding of Binary_ frames
and return a string (:class:`str`). This may be useful for
servers that send binary frames instead of text frames.
Raises:
ConnectionClosed: When the connection is closed.
ConcurrencyError: If two threads call :meth:`recv` or
:meth:`recv_streaming` concurrently.
"""
try:
return self.recv_messages.get(timeout, decode)
except EOFError:
pass
# fallthrough
except ConcurrencyError:
raise ConcurrencyError(
"cannot call recv while another thread "
"is already running recv or recv_streaming"
) from None
except UnicodeDecodeError as exc:
with self.send_context():
self.protocol.fail(
CloseCode.INVALID_DATA,
f"{exc.reason} at position {exc.start}",
)
# fallthrough
# Wait for the protocol state to be CLOSED before accessing close_exc.
self.recv_events_thread.join()
raise self.protocol.close_exc from self.recv_exc
@overload
def recv_streaming(self, decode: Literal[True]) -> Iterator[str]: ...
@overload
def recv_streaming(self, decode: Literal[False]) -> Iterator[bytes]: ...
@overload
def recv_streaming(self, decode: bool | None = None) -> Iterator[Data]: ...
def recv_streaming(self, decode: bool | None = None) -> Iterator[Data]:
"""
Receive the next message frame by frame.
This method is designed for receiving fragmented messages. It returns an
iterator that yields each fragment as it is received. This iterator must
be fully consumed. Else, future calls to :meth:`recv` or
:meth:`recv_streaming` will raise
:exc:`~websockets.exceptions.ConcurrencyError`, making the connection
unusable.
:meth:`recv_streaming` raises the same exceptions as :meth:`recv`.
Args:
decode: Set this flag to override the default behavior of returning
:class:`str` or :class:`bytes`. See below for details.
Returns:
An iterator of strings (:class:`str`) for a Text_ frame or
bytestrings (:class:`bytes`) for a Binary_ frame.
.. _Text: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
.. _Binary: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
You may override this behavior with the ``decode`` argument:
* Set ``decode=False`` to disable UTF-8 decoding of Text_ frames
and return bytestrings (:class:`bytes`). This may be useful to
optimize performance when decoding isn't needed.
* Set ``decode=True`` to force UTF-8 decoding of Binary_ frames
and return strings (:class:`str`). This is useful for servers
that send binary frames instead of text frames.
Raises:
ConnectionClosed: When the connection is closed.
ConcurrencyError: If two threads call :meth:`recv` or
:meth:`recv_streaming` concurrently.
"""
try:
yield from self.recv_messages.get_iter(decode)
return
except EOFError:
pass
# fallthrough
except ConcurrencyError:
raise ConcurrencyError(
"cannot call recv_streaming while another thread "
"is already running recv or recv_streaming"
) from None
except UnicodeDecodeError as exc:
with self.send_context():
self.protocol.fail(
CloseCode.INVALID_DATA,
f"{exc.reason} at position {exc.start}",
)
# fallthrough
# Wait for the protocol state to be CLOSED before accessing close_exc.
self.recv_events_thread.join()
raise self.protocol.close_exc from self.recv_exc
def send(
self,
message: Data | Iterable[Data],
text: bool | None = None,
) -> None:
"""
Send a message.
A string (:class:`str`) is sent as a Text_ frame. A bytestring or
bytes-like object (:class:`bytes`, :class:`bytearray`, or
:class:`memoryview`) is sent as a Binary_ frame.
.. _Text: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
.. _Binary: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
You may override this behavior with the ``text`` argument:
* Set ``text=True`` to send a bytestring or bytes-like object
(:class:`bytes`, :class:`bytearray`, or :class:`memoryview`) as a
Text_ frame. This improves performance when the message is already
UTF-8 encoded, for example if the message contains JSON and you're
using a JSON library that produces a bytestring.
* Set ``text=False`` to send a string (:class:`str`) in a Binary_
frame. This may be useful for servers that expect binary frames
instead of text frames.
:meth:`send` also accepts an iterable of strings, bytestrings, or
bytes-like objects to enable fragmentation_. Each item is treated as a
message fragment and sent in its own frame. All items must be of the
same type, or else :meth:`send` will raise a :exc:`TypeError` and the
connection will be closed.
.. _fragmentation: https://datatracker.ietf.org/doc/html/rfc6455#section-5.4
:meth:`send` rejects dict-like objects because this is often an error.
(If you really want to send the keys of a dict-like object as fragments,
call its :meth:`~dict.keys` method and pass the result to :meth:`send`.)
When the connection is closed, :meth:`send` raises
:exc:`~websockets.exceptions.ConnectionClosed`. Specifically, it
raises :exc:`~websockets.exceptions.ConnectionClosedOK` after a normal
connection closure and
:exc:`~websockets.exceptions.ConnectionClosedError` after a protocol
error or a network failure.
Args:
message: Message to send.
Raises:
ConnectionClosed: When the connection is closed.
ConcurrencyError: If the connection is sending a fragmented message.
TypeError: If ``message`` doesn't have a supported type.
"""
# Unfragmented message -- this case must be handled first because
# strings and bytes-like objects are iterable.
if isinstance(message, str):
with self.send_context():
if self.send_in_progress:
raise ConcurrencyError(
"cannot call send while another thread is already running send"
)
if text is False:
self.protocol.send_binary(message.encode())
else:
self.protocol.send_text(message.encode())
elif isinstance(message, BytesLike):
with self.send_context():
if self.send_in_progress:
raise ConcurrencyError(
"cannot call send while another thread is already running send"
)
if text is True:
self.protocol.send_text(message)
else:
self.protocol.send_binary(message)
# Catch a common mistake -- passing a dict to send().
elif isinstance(message, Mapping):
raise TypeError("data is a dict-like object")
# Fragmented message -- regular iterator.
elif isinstance(message, Iterable):
chunks = iter(message)
try:
chunk = next(chunks)
except StopIteration:
return
try:
# First fragment.
if isinstance(chunk, str):
with self.send_context():
if self.send_in_progress:
raise ConcurrencyError(
"cannot call send while another thread "
"is already running send"
)
self.send_in_progress = True
if text is False:
self.protocol.send_binary(chunk.encode(), fin=False)
else:
self.protocol.send_text(chunk.encode(), fin=False)
encode = True
elif isinstance(chunk, BytesLike):
with self.send_context():
if self.send_in_progress:
raise ConcurrencyError(
"cannot call send while another thread "
"is already running send"
)
self.send_in_progress = True
if text is True:
self.protocol.send_text(chunk, fin=False)
else:
self.protocol.send_binary(chunk, fin=False)
encode = False
else:
raise TypeError("data iterable must contain bytes or str")
# Other fragments
for chunk in chunks:
if isinstance(chunk, str) and encode:
with self.send_context():
assert self.send_in_progress
self.protocol.send_continuation(chunk.encode(), fin=False)
elif isinstance(chunk, BytesLike) and not encode:
with self.send_context():
assert self.send_in_progress
self.protocol.send_continuation(chunk, fin=False)
else:
raise TypeError("data iterable must contain uniform types")
# Final fragment.
with self.send_context():
self.protocol.send_continuation(b"", fin=True)
self.send_in_progress = False
except ConcurrencyError:
# We didn't start sending a fragmented message.
# The connection is still usable.
raise
except Exception:
# We're half-way through a fragmented message and we can't
# complete it. This makes the connection unusable.
with self.send_context():
self.protocol.fail(
CloseCode.INTERNAL_ERROR,
"error in fragmented message",
)
raise
else:
raise TypeError("data must be str, bytes, or iterable")
def close(self, code: int = CloseCode.NORMAL_CLOSURE, reason: str = "") -> None:
"""
Perform the closing handshake.
:meth:`close` waits for the other end to complete the handshake, for the
TCP connection to terminate, and for all incoming messages to be read
with :meth:`recv`.
:meth:`close` is idempotent: it doesn't do anything once the
connection is closed.
Args:
code: WebSocket close code.
reason: WebSocket close reason.
"""
try:
# The context manager takes care of waiting for the TCP connection
# to terminate after calling a method that sends a close frame.
with self.send_context():
if self.send_in_progress:
self.protocol.fail(
CloseCode.INTERNAL_ERROR,
"close during fragmented message",
)
else:
self.protocol.send_close(code, reason)
except ConnectionClosed:
# Ignore ConnectionClosed exceptions raised from send_context().
# They mean that the connection is closed, which was the goal.
pass
def ping(
self,
data: Data | None = None,
ack_on_close: bool = False,
) -> threading.Event:
"""
Send a Ping_.
.. _Ping: https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.2
A ping may serve as a keepalive or as a check that the remote endpoint
received all messages up to this point
Args:
data: Payload of the ping. A :class:`str` will be encoded to UTF-8.
If ``data`` is :obj:`None`, the payload is four random bytes.
ack_on_close: when this option is :obj:`True`, the event will also
be set when the connection is closed. While this avoids getting
stuck waiting for a pong that will never arrive, it requires
checking that the state of the connection is still ``OPEN`` to
confirm that a pong was received, rather than the connection
being closed.
Returns:
An event that will be set when the corresponding pong is received.
You can ignore it if you don't intend to wait.
::
pong_event = ws.ping()
pong_event.wait() # only if you want to wait for the pong
Raises:
ConnectionClosed: When the connection is closed.
ConcurrencyError: If another ping was sent with the same data and
the corresponding pong wasn't received yet.
"""
if isinstance(data, BytesLike):
data = bytes(data)
elif isinstance(data, str):
data = data.encode()
elif data is not None:
raise TypeError("data must be str or bytes-like")
with self.send_context():
# Protect against duplicates if a payload is explicitly set.
if data in self.pong_waiters:
raise ConcurrencyError("already waiting for a pong with the same data")
# Generate a unique random payload otherwise.
while data is None or data in self.pong_waiters:
data = struct.pack("!I", random.getrandbits(32))
pong_waiter = threading.Event()
self.pong_waiters[data] = (pong_waiter, time.monotonic(), ack_on_close)
self.protocol.send_ping(data)
return pong_waiter
def pong(self, data: Data = b"") -> None:
"""
Send a Pong_.
.. _Pong: https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.3
An unsolicited pong may serve as a unidirectional heartbeat.
Args:
data: Payload of the pong. A :class:`str` will be encoded to UTF-8.
Raises:
ConnectionClosed: When the connection is closed.
"""
if isinstance(data, BytesLike):
data = bytes(data)
elif isinstance(data, str):
data = data.encode()
else:
raise TypeError("data must be str or bytes-like")
with self.send_context():
self.protocol.send_pong(data)
# Private methods
def process_event(self, event: Event) -> None:
"""
Process one incoming event.
This method is overridden in subclasses to handle the handshake.
"""
assert isinstance(event, Frame)
if event.opcode in DATA_OPCODES:
self.recv_messages.put(event)
if event.opcode is Opcode.PONG:
self.acknowledge_pings(bytes(event.data))
def acknowledge_pings(self, data: bytes) -> None:
"""
Acknowledge pings when receiving a pong.
"""
with self.protocol_mutex:
# Ignore unsolicited pong.
if data not in self.pong_waiters:
return
pong_timestamp = time.monotonic()
# Sending a pong for only the most recent ping is legal.
# Acknowledge all previous pings too in that case.
ping_id = None
ping_ids = []
for ping_id, (
pong_waiter,
ping_timestamp,
_ack_on_close,
) in self.pong_waiters.items():
ping_ids.append(ping_id)
pong_waiter.set()
if ping_id == data:
self.latency = pong_timestamp - ping_timestamp
break
else:
raise AssertionError("solicited pong not found in pings")
# Remove acknowledged pings from self.pong_waiters.
for ping_id in ping_ids:
del self.pong_waiters[ping_id]
def acknowledge_pending_pings(self) -> None:
"""
Acknowledge pending pings when the connection is closed.
"""
assert self.protocol.state is CLOSED
for pong_waiter, _ping_timestamp, ack_on_close in self.pong_waiters.values():
if ack_on_close:
pong_waiter.set()
self.pong_waiters.clear()
def keepalive(self) -> None:
"""
Send a Ping frame and wait for a Pong frame at regular intervals.
"""
assert self.ping_interval is not None
try:
while True:
# If self.ping_timeout > self.latency > self.ping_interval,
# pings will be sent immediately after receiving pongs.
# The period will be longer than self.ping_interval.
self.recv_events_thread.join(self.ping_interval - self.latency)
if not self.recv_events_thread.is_alive():
break
try:
pong_waiter = self.ping(ack_on_close=True)
except ConnectionClosed:
break
if self.debug:
self.logger.debug("% sent keepalive ping")
if self.ping_timeout is not None:
#
if pong_waiter.wait(self.ping_timeout):
if self.debug:
self.logger.debug("% received keepalive pong")
else:
if self.debug:
self.logger.debug("- timed out waiting for keepalive pong")
with self.send_context():
self.protocol.fail(
CloseCode.INTERNAL_ERROR,
"keepalive ping timeout",
)
break
except Exception:
self.logger.error("keepalive ping failed", exc_info=True)
def start_keepalive(self) -> None:
"""
Run :meth:`keepalive` in a thread, unless keepalive is disabled.
"""
if self.ping_interval is not None:
# This thread is marked as daemon like self.recv_events_thread.
self.keepalive_thread = threading.Thread(
target=self.keepalive,
daemon=True,
)
self.keepalive_thread.start()
def recv_events(self) -> None:
"""
Read incoming data from the socket and process events.
Run this method in a thread as long as the connection is alive.
``recv_events()`` exits immediately when the ``self.socket`` is closed.
"""
try:
while True:
try:
with self.recv_flow_control:
if self.close_deadline is not None:
self.socket.settimeout(self.close_deadline.timeout())
data = self.socket.recv(self.recv_bufsize)
except Exception as exc:
if self.debug:
self.logger.debug(
"! error while receiving data",
exc_info=True,
)
# When the closing handshake is initiated by our side,
# recv() may block until send_context() closes the socket.
# In that case, send_context() already set recv_exc.
# Calling set_recv_exc() avoids overwriting it.
with self.protocol_mutex:
self.set_recv_exc(exc)
break
if data == b"":
break
# Acquire the connection lock.
with self.protocol_mutex:
# Feed incoming data to the protocol.
self.protocol.receive_data(data)
# This isn't expected to raise an exception.
events = self.protocol.events_received()
# Write outgoing data to the socket.
try:
self.send_data()
except Exception as exc:
if self.debug:
self.logger.debug(
"! error while sending data",
exc_info=True,
)
# Similarly to the above, avoid overriding an exception
# set by send_context(), in case of a race condition
# i.e. send_context() closes the socket after recv()
# returns above but before send_data() calls send().
self.set_recv_exc(exc)
break
if self.protocol.close_expected():
# If the connection is expected to close soon, set the
# close deadline based on the close timeout.
if self.close_deadline is None:
self.close_deadline = Deadline(self.close_timeout)
# Unlock conn_mutex before processing events. Else, the
# application can't send messages in response to events.
# If self.send_data raised an exception, then events are lost.
# Given that automatic responses write small amounts of data,
# this should be uncommon, so we don't handle the edge case.
for event in events:
# This isn't expected to raise an exception.
self.process_event(event)
# Breaking out of the while True: ... loop means that we believe
# that the socket doesn't work anymore.
with self.protocol_mutex:
# Feed the end of the data stream to the protocol.
self.protocol.receive_eof()
# This isn't expected to raise an exception.
events = self.protocol.events_received()
# There is no error handling because send_data() can only write
# the end of the data stream here and it handles errors itself.
self.send_data()
# This code path is triggered when receiving an HTTP response
# without a Content-Length header. This is the only case where
# reading until EOF generates an event; all other events have
# a known length. Ignore for coverage measurement because tests
# are in test_client.py rather than test_connection.py.
for event in events: # pragma: no cover
# This isn't expected to raise an exception.
self.process_event(event)
except Exception as exc:
# This branch should never run. It's a safety net in case of bugs.
self.logger.error("unexpected internal error", exc_info=True)
with self.protocol_mutex:
self.set_recv_exc(exc)
finally:
# This isn't expected to raise an exception.
self.close_socket()
@contextlib.contextmanager
def send_context(
self,
*,
expected_state: State = OPEN, # CONNECTING during the opening handshake
) -> Iterator[None]:
"""
Create a context for writing to the connection from user code.
On entry, :meth:`send_context` acquires the connection lock and checks
that the connection is open; on exit, it writes outgoing data to the
socket::
with self.send_context():
self.protocol.send_text(message.encode())
When the connection isn't open on entry, when the connection is expected
to close on exit, or when an unexpected error happens, terminating the
connection, :meth:`send_context` waits until the connection is closed
then raises :exc:`~websockets.exceptions.ConnectionClosed`.
"""
# Should we wait until the connection is closed?
wait_for_close = False
# Should we close the socket and raise ConnectionClosed?
raise_close_exc = False
# What exception should we chain ConnectionClosed to?
original_exc: BaseException | None = None
# Acquire the protocol lock.
with self.protocol_mutex:
if self.protocol.state is expected_state:
# Let the caller interact with the protocol.
try:
yield
except (ProtocolError, ConcurrencyError):
# The protocol state wasn't changed. Exit immediately.
raise
except Exception as exc:
self.logger.error("unexpected internal error", exc_info=True)
# This branch should never run. It's a safety net in case of
# bugs. Since we don't know what happened, we will close the
# connection and raise the exception to the caller.
wait_for_close = False
raise_close_exc = True
original_exc = exc
else:
# Check if the connection is expected to close soon.
if self.protocol.close_expected():
wait_for_close = True
# If the connection is expected to close soon, set the
# close deadline based on the close timeout.
# Since we tested earlier that protocol.state was OPEN
# (or CONNECTING) and we didn't release protocol_mutex,
# it is certain that self.close_deadline is still None.
assert self.close_deadline is None
self.close_deadline = Deadline(self.close_timeout)
# Write outgoing data to the socket.
try:
self.send_data()
except Exception as exc:
if self.debug:
self.logger.debug(
"! error while sending data",
exc_info=True,
)
# While the only expected exception here is OSError,
# other exceptions would be treated identically.
wait_for_close = False
raise_close_exc = True
original_exc = exc
else: # self.protocol.state is not expected_state
# Minor layering violation: we assume that the connection
# will be closing soon if it isn't in the expected state.
wait_for_close = True
raise_close_exc = True
# To avoid a deadlock, release the connection lock by exiting the
# context manager before waiting for recv_events() to terminate.
# If the connection is expected to close soon and the close timeout
# elapses, close the socket to terminate the connection.
if wait_for_close:
if self.close_deadline is None:
timeout = self.close_timeout
else:
# Thread.join() returns immediately if timeout is negative.
timeout = self.close_deadline.timeout(raise_if_elapsed=False)
self.recv_events_thread.join(timeout)
if self.recv_events_thread.is_alive():
# There's no risk to overwrite another error because
# original_exc is never set when wait_for_close is True.
assert original_exc is None
original_exc = TimeoutError("timed out while closing connection")
# Set recv_exc before closing the socket in order to get
# proper exception reporting.
raise_close_exc = True
with self.protocol_mutex:
self.set_recv_exc(original_exc)
# If an error occurred, close the socket to terminate the connection and
# raise an exception.
if raise_close_exc:
self.close_socket()
# Wait for the protocol state to be CLOSED before accessing close_exc.
self.recv_events_thread.join()
raise self.protocol.close_exc from original_exc
def send_data(self) -> None:
"""
Send outgoing data.
This method requires holding protocol_mutex.
Raises:
OSError: When a socket operations fails.
"""
assert self.protocol_mutex.locked()
for data in self.protocol.data_to_send():
if data:
if self.close_deadline is not None:
self.socket.settimeout(self.close_deadline.timeout())
self.socket.sendall(data)
else:
try:
self.socket.shutdown(socket.SHUT_WR)
except OSError: # socket already closed
pass
def set_recv_exc(self, exc: BaseException | None) -> None:
"""
Set recv_exc, if not set yet.
This method requires holding protocol_mutex.
"""
assert self.protocol_mutex.locked()
if self.recv_exc is None: # pragma: no branch
self.recv_exc = exc
def close_socket(self) -> None:
"""
Shutdown and close socket. Close message assembler.
Calling close_socket() guarantees that recv_events() terminates. Indeed,
recv_events() may block only on socket.recv() or on recv_messages.put().
"""
# shutdown() is required to interrupt recv() on Linux.
try:
self.socket.shutdown(socket.SHUT_RDWR)
except OSError:
pass # socket is already closed
self.socket.close()
# Calling protocol.receive_eof() is safe because it's idempotent.
# This guarantees that the protocol state becomes CLOSED.
with self.protocol_mutex:
self.protocol.receive_eof()
assert self.protocol.state is CLOSED
# Abort recv() with a ConnectionClosed exception.
self.recv_messages.close()
# Acknowledge pings sent with the ack_on_close option.
self.acknowledge_pending_pings()
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