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#
# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""A utility class for event-based messaging on a zmq socket using tornado.
.. seealso::
- :mod:`zmq.asyncio`
- :mod:`zmq.eventloop.future`
"""
import asyncio
import pickle
import warnings
from queue import Queue
from typing import (
Any,
Awaitable,
Callable,
List,
Optional,
Sequence,
Union,
cast,
overload,
)
from tornado.ioloop import IOLoop
from tornado.log import gen_log
import zmq
import zmq._future
from zmq import POLLIN, POLLOUT
from zmq._typing import Literal
from zmq.utils import jsonapi
class ZMQStream:
"""A utility class to register callbacks when a zmq socket sends and receives
For use with tornado IOLoop.
There are three main methods
Methods:
* **on_recv(callback, copy=True):**
register a callback to be run every time the socket has something to receive
* **on_send(callback):**
register a callback to be run every time you call send
* **send_multipart(self, msg, flags=0, copy=False, callback=None):**
perform a send that will trigger the callback
if callback is passed, on_send is also called.
There are also send_multipart(), send_json(), send_pyobj()
Three other methods for deactivating the callbacks:
* **stop_on_recv():**
turn off the recv callback
* **stop_on_send():**
turn off the send callback
which simply call ``on_<evt>(None)``.
The entire socket interface, excluding direct recv methods, is also
provided, primarily through direct-linking the methods.
e.g.
>>> stream.bind is stream.socket.bind
True
.. versionadded:: 25
send/recv callbacks can be coroutines.
.. versionchanged:: 25
ZMQStreams only support base zmq.Socket classes (this has always been true, but not enforced).
If ZMQStreams are created with e.g. async Socket subclasses,
a RuntimeWarning will be shown,
and the socket cast back to the default zmq.Socket
before connecting events.
Previously, using async sockets (or any zmq.Socket subclass) would result in undefined behavior for the
arguments passed to callback functions.
Now, the callback functions reliably get the return value of the base `zmq.Socket` send/recv_multipart methods
(the list of message frames).
"""
socket: zmq.Socket
io_loop: IOLoop
poller: zmq.Poller
_send_queue: Queue
_recv_callback: Optional[Callable]
_send_callback: Optional[Callable]
_close_callback: Optional[Callable]
_state: int = 0
_flushed: bool = False
_recv_copy: bool = False
_fd: int
def __init__(self, socket: "zmq.Socket", io_loop: Optional[IOLoop] = None):
if isinstance(socket, zmq._future._AsyncSocket):
warnings.warn(
f"""ZMQStream only supports the base zmq.Socket class.
Use zmq.Socket(shadow=other_socket)
or `ctx.socket(zmq.{socket._type_name}, socket_class=zmq.Socket)`
to create a base zmq.Socket object,
no matter what other kind of socket your Context creates.
""",
RuntimeWarning,
stacklevel=2,
)
# shadow back to base zmq.Socket,
# otherwise callbacks like `on_recv` will get the wrong types.
socket = zmq.Socket(shadow=socket)
self.socket = socket
# IOLoop.current() is deprecated if called outside the event loop
# that means
self.io_loop = io_loop or IOLoop.current()
self.poller = zmq.Poller()
self._fd = cast(int, self.socket.FD)
self._send_queue = Queue()
self._recv_callback = None
self._send_callback = None
self._close_callback = None
self._recv_copy = False
self._flushed = False
self._state = 0
self._init_io_state()
# shortcircuit some socket methods
self.bind = self.socket.bind
self.bind_to_random_port = self.socket.bind_to_random_port
self.connect = self.socket.connect
self.setsockopt = self.socket.setsockopt
self.getsockopt = self.socket.getsockopt
self.setsockopt_string = self.socket.setsockopt_string
self.getsockopt_string = self.socket.getsockopt_string
self.setsockopt_unicode = self.socket.setsockopt_unicode
self.getsockopt_unicode = self.socket.getsockopt_unicode
def stop_on_recv(self):
"""Disable callback and automatic receiving."""
return self.on_recv(None)
def stop_on_send(self):
"""Disable callback on sending."""
return self.on_send(None)
def stop_on_err(self):
"""DEPRECATED, does nothing"""
gen_log.warn("on_err does nothing, and will be removed")
def on_err(self, callback: Callable):
"""DEPRECATED, does nothing"""
gen_log.warn("on_err does nothing, and will be removed")
@overload
def on_recv(
self,
callback: Callable[[List[bytes]], Any],
) -> None:
...
@overload
def on_recv(
self,
callback: Callable[[List[bytes]], Any],
copy: Literal[True],
) -> None:
...
@overload
def on_recv(
self,
callback: Callable[[List[zmq.Frame]], Any],
copy: Literal[False],
) -> None:
...
@overload
def on_recv(
self,
callback: Union[
Callable[[List[zmq.Frame]], Any],
Callable[[List[bytes]], Any],
],
copy: bool = ...,
):
...
def on_recv(
self,
callback: Union[
Callable[[List[zmq.Frame]], Any],
Callable[[List[bytes]], Any],
],
copy: bool = True,
) -> None:
"""Register a callback for when a message is ready to recv.
There can be only one callback registered at a time, so each
call to `on_recv` replaces previously registered callbacks.
on_recv(None) disables recv event polling.
Use on_recv_stream(callback) instead, to register a callback that will receive
both this ZMQStream and the message, instead of just the message.
Parameters
----------
callback : callable
callback must take exactly one argument, which will be a
list, as returned by socket.recv_multipart()
if callback is None, recv callbacks are disabled.
copy : bool
copy is passed directly to recv, so if copy is False,
callback will receive Message objects. If copy is True,
then callback will receive bytes/str objects.
Returns : None
"""
self._check_closed()
assert callback is None or callable(callback)
self._recv_callback = callback
self._recv_copy = copy
if callback is None:
self._drop_io_state(zmq.POLLIN)
else:
self._add_io_state(zmq.POLLIN)
@overload
def on_recv_stream(
self,
callback: Callable[["ZMQStream", List[bytes]], Any],
) -> None:
...
@overload
def on_recv_stream(
self,
callback: Callable[["ZMQStream", List[bytes]], Any],
copy: Literal[True],
) -> None:
...
@overload
def on_recv_stream(
self,
callback: Callable[["ZMQStream", List[zmq.Frame]], Any],
copy: Literal[False],
) -> None:
...
@overload
def on_recv_stream(
self,
callback: Union[
Callable[["ZMQStream", List[zmq.Frame]], Any],
Callable[["ZMQStream", List[bytes]], Any],
],
copy: bool = ...,
):
...
def on_recv_stream(
self,
callback: Union[
Callable[["ZMQStream", List[zmq.Frame]], Any],
Callable[["ZMQStream", List[bytes]], Any],
],
copy: bool = True,
):
"""Same as on_recv, but callback will get this stream as first argument
callback must take exactly two arguments, as it will be called as::
callback(stream, msg)
Useful when a single callback should be used with multiple streams.
"""
if callback is None:
self.stop_on_recv()
else:
def stream_callback(msg):
return callback(self, msg)
self.on_recv(stream_callback, copy=copy)
def on_send(
self, callback: Callable[[Sequence[Any], Optional[zmq.MessageTracker]], Any]
):
"""Register a callback to be called on each send
There will be two arguments::
callback(msg, status)
* `msg` will be the list of sendable objects that was just sent
* `status` will be the return result of socket.send_multipart(msg) -
MessageTracker or None.
Non-copying sends return a MessageTracker object whose
`done` attribute will be True when the send is complete.
This allows users to track when an object is safe to write to
again.
The second argument will always be None if copy=True
on the send.
Use on_send_stream(callback) to register a callback that will be passed
this ZMQStream as the first argument, in addition to the other two.
on_send(None) disables recv event polling.
Parameters
----------
callback : callable
callback must take exactly two arguments, which will be
the message being sent (always a list),
and the return result of socket.send_multipart(msg) -
MessageTracker or None.
if callback is None, send callbacks are disabled.
"""
self._check_closed()
assert callback is None or callable(callback)
self._send_callback = callback
def on_send_stream(
self,
callback: Callable[
["ZMQStream", Sequence[Any], Optional[zmq.MessageTracker]], Any
],
):
"""Same as on_send, but callback will get this stream as first argument
Callback will be passed three arguments::
callback(stream, msg, status)
Useful when a single callback should be used with multiple streams.
"""
if callback is None:
self.stop_on_send()
else:
self.on_send(lambda msg, status: callback(self, msg, status))
def send(self, msg, flags=0, copy=True, track=False, callback=None, **kwargs):
"""Send a message, optionally also register a new callback for sends.
See zmq.socket.send for details.
"""
return self.send_multipart(
[msg], flags=flags, copy=copy, track=track, callback=callback, **kwargs
)
def send_multipart(
self,
msg: Sequence[Any],
flags: int = 0,
copy: bool = True,
track: bool = False,
callback: Optional[Callable] = None,
**kwargs: Any,
) -> None:
"""Send a multipart message, optionally also register a new callback for sends.
See zmq.socket.send_multipart for details.
"""
kwargs.update(dict(flags=flags, copy=copy, track=track))
self._send_queue.put((msg, kwargs))
callback = callback or self._send_callback
if callback is not None:
self.on_send(callback)
else:
# noop callback
self.on_send(lambda *args: None)
self._add_io_state(zmq.POLLOUT)
def send_string(
self,
u: str,
flags: int = 0,
encoding: str = 'utf-8',
callback: Optional[Callable] = None,
**kwargs: Any,
):
"""Send a unicode message with an encoding.
See zmq.socket.send_unicode for details.
"""
if not isinstance(u, str):
raise TypeError("unicode/str objects only")
return self.send(u.encode(encoding), flags=flags, callback=callback, **kwargs)
send_unicode = send_string
def send_json(
self,
obj: Any,
flags: int = 0,
callback: Optional[Callable] = None,
**kwargs: Any,
):
"""Send json-serialized version of an object.
See zmq.socket.send_json for details.
"""
msg = jsonapi.dumps(obj)
return self.send(msg, flags=flags, callback=callback, **kwargs)
def send_pyobj(
self,
obj: Any,
flags: int = 0,
protocol: int = -1,
callback: Optional[Callable] = None,
**kwargs: Any,
):
"""Send a Python object as a message using pickle to serialize.
See zmq.socket.send_json for details.
"""
msg = pickle.dumps(obj, protocol)
return self.send(msg, flags, callback=callback, **kwargs)
def _finish_flush(self):
"""callback for unsetting _flushed flag."""
self._flushed = False
def flush(self, flag: int = zmq.POLLIN | zmq.POLLOUT, limit: Optional[int] = None):
"""Flush pending messages.
This method safely handles all pending incoming and/or outgoing messages,
bypassing the inner loop, passing them to the registered callbacks.
A limit can be specified, to prevent blocking under high load.
flush will return the first time ANY of these conditions are met:
* No more events matching the flag are pending.
* the total number of events handled reaches the limit.
Note that if ``flag|POLLIN != 0``, recv events will be flushed even if no callback
is registered, unlike normal IOLoop operation. This allows flush to be
used to remove *and ignore* incoming messages.
Parameters
----------
flag : int, default=POLLIN|POLLOUT
0MQ poll flags.
If flag|POLLIN, recv events will be flushed.
If flag|POLLOUT, send events will be flushed.
Both flags can be set at once, which is the default.
limit : None or int, optional
The maximum number of messages to send or receive.
Both send and recv count against this limit.
Returns
-------
int : count of events handled (both send and recv)
"""
self._check_closed()
# unset self._flushed, so callbacks will execute, in case flush has
# already been called this iteration
already_flushed = self._flushed
self._flushed = False
# initialize counters
count = 0
def update_flag():
"""Update the poll flag, to prevent registering POLLOUT events
if we don't have pending sends."""
return flag & zmq.POLLIN | (self.sending() and flag & zmq.POLLOUT)
flag = update_flag()
if not flag:
# nothing to do
return 0
self.poller.register(self.socket, flag)
events = self.poller.poll(0)
while events and (not limit or count < limit):
s, event = events[0]
if event & POLLIN: # receiving
self._handle_recv()
count += 1
if self.socket is None:
# break if socket was closed during callback
break
if event & POLLOUT and self.sending():
self._handle_send()
count += 1
if self.socket is None:
# break if socket was closed during callback
break
flag = update_flag()
if flag:
self.poller.register(self.socket, flag)
events = self.poller.poll(0)
else:
events = []
if count: # only bypass loop if we actually flushed something
# skip send/recv callbacks this iteration
self._flushed = True
# reregister them at the end of the loop
if not already_flushed: # don't need to do it again
self.io_loop.add_callback(self._finish_flush)
elif already_flushed:
self._flushed = True
# update ioloop poll state, which may have changed
self._rebuild_io_state()
return count
def set_close_callback(self, callback: Optional[Callable]):
"""Call the given callback when the stream is closed."""
self._close_callback = callback
def close(self, linger: Optional[int] = None) -> None:
"""Close this stream."""
if self.socket is not None:
if self.socket.closed:
# fallback on raw fd for closed sockets
# hopefully this happened promptly after close,
# otherwise somebody else may have the FD
warnings.warn(
"Unregistering FD %s after closing socket. "
"This could result in unregistering handlers for the wrong socket. "
"Please use stream.close() instead of closing the socket directly."
% self._fd,
stacklevel=2,
)
self.io_loop.remove_handler(self._fd)
else:
self.io_loop.remove_handler(self.socket)
self.socket.close(linger)
self.socket = None # type: ignore
if self._close_callback:
self._run_callback(self._close_callback)
def receiving(self) -> bool:
"""Returns True if we are currently receiving from the stream."""
return self._recv_callback is not None
def sending(self) -> bool:
"""Returns True if we are currently sending to the stream."""
return not self._send_queue.empty()
def closed(self) -> bool:
if self.socket is None:
return True
if self.socket.closed:
# underlying socket has been closed, but not by us!
# trigger our cleanup
self.close()
return True
return False
def _run_callback(self, callback, *args, **kwargs):
"""Wrap running callbacks in try/except to allow us to
close our socket."""
try:
f = callback(*args, **kwargs)
if isinstance(f, Awaitable):
f = asyncio.ensure_future(f)
else:
f = None
except Exception:
gen_log.error("Uncaught exception in ZMQStream callback", exc_info=True)
# Re-raise the exception so that IOLoop.handle_callback_exception
# can see it and log the error
raise
if f is not None:
# handle async callbacks
def _log_error(f):
try:
f.result()
except Exception:
gen_log.error(
"Uncaught exception in ZMQStream callback", exc_info=True
)
f.add_done_callback(_log_error)
def _handle_events(self, fd, events):
"""This method is the actual handler for IOLoop, that gets called whenever
an event on my socket is posted. It dispatches to _handle_recv, etc."""
if not self.socket:
gen_log.warning("Got events for closed stream %s", self)
return
try:
zmq_events = self.socket.EVENTS
except zmq.ContextTerminated:
gen_log.warning("Got events for stream %s after terminating context", self)
# trigger close check, this will unregister callbacks
self.closed()
return
except zmq.ZMQError as e:
# run close check
# shadow sockets may have been closed elsewhere,
# which should show up as ENOTSOCK here
if self.closed():
gen_log.warning(
"Got events for stream %s attached to closed socket: %s", self, e
)
else:
gen_log.error("Error getting events for %s: %s", self, e)
return
try:
# dispatch events:
if zmq_events & zmq.POLLIN and self.receiving():
self._handle_recv()
if not self.socket:
return
if zmq_events & zmq.POLLOUT and self.sending():
self._handle_send()
if not self.socket:
return
# rebuild the poll state
self._rebuild_io_state()
except Exception:
gen_log.error("Uncaught exception in zmqstream callback", exc_info=True)
raise
def _handle_recv(self):
"""Handle a recv event."""
if self._flushed:
return
try:
msg = self.socket.recv_multipart(zmq.NOBLOCK, copy=self._recv_copy)
except zmq.ZMQError as e:
if e.errno == zmq.EAGAIN:
# state changed since poll event
pass
else:
raise
else:
if self._recv_callback:
callback = self._recv_callback
self._run_callback(callback, msg)
def _handle_send(self):
"""Handle a send event."""
if self._flushed:
return
if not self.sending():
gen_log.error("Shouldn't have handled a send event")
return
msg, kwargs = self._send_queue.get()
try:
status = self.socket.send_multipart(msg, **kwargs)
except zmq.ZMQError as e:
gen_log.error("SEND Error: %s", e)
status = e
if self._send_callback:
callback = self._send_callback
self._run_callback(callback, msg, status)
def _check_closed(self):
if not self.socket:
raise OSError("Stream is closed")
def _rebuild_io_state(self):
"""rebuild io state based on self.sending() and receiving()"""
if self.socket is None:
return
state = 0
if self.receiving():
state |= zmq.POLLIN
if self.sending():
state |= zmq.POLLOUT
self._state = state
self._update_handler(state)
def _add_io_state(self, state):
"""Add io_state to poller."""
self._state = self._state | state
self._update_handler(self._state)
def _drop_io_state(self, state):
"""Stop poller from watching an io_state."""
self._state = self._state & (~state)
self._update_handler(self._state)
def _update_handler(self, state):
"""Update IOLoop handler with state."""
if self.socket is None:
return
if state & self.socket.events:
# events still exist that haven't been processed
# explicitly schedule handling to avoid missing events due to edge-triggered FDs
self.io_loop.add_callback(lambda: self._handle_events(self.socket, 0))
def _init_io_state(self):
"""initialize the ioloop event handler"""
self.io_loop.add_handler(self.socket, self._handle_events, self.io_loop.READ)