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zmqstream.py
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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 to send to and recv from a non-blocking socket, using tornado. .. seealso:: - :mod:`zmq.asyncio` - :mod:`zmq.eventloop.future` """ import pickle import sys import warnings from queue import Queue from typing import Any, Callable, List, Optional, Sequence, Union, cast, overload import zmq from zmq._typing import Literal from zmq.utils import jsonapi from .ioloop import IOLoop, gen_log try: import tornado.ioloop from tornado.stack_context import wrap as stack_context_wrap # type: ignore except ImportError: if "zmq.eventloop.minitornado" in sys.modules: from .minitornado.stack_context import ( wrap as stack_context_wrap, # type: ignore ) else: # tornado 5 deprecates stack_context, # tornado 6 removes it def stack_context_wrap(callback): return callback class ZMQStream: """A utility class to register callbacks when a zmq socket sends and receives For use with zmq.eventloop.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(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 """ socket: zmq.Socket io_loop: "tornado.ioloop.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["tornado.ioloop.IOLoop"] = None ): self.socket = socket 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 = stack_context_wrap(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 = stack_context_wrap(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: 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 & zmq.POLLIN: # receiving self._handle_recv() count += 1 if self.socket is None: # break if socket was closed during callback break if event & zmq.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 = stack_context_wrap(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: # Use a NullContext to ensure that all StackContexts are run # inside our blanket exception handler rather than outside. callback(*args, **kwargs) 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 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) 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)