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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."""
import sys
import logging
import zmq
from zmq.core.socket import jsonapi, pickle
from tornado import ioloop
from tornado import stack_context
try:
from queue import Queue
except ImportError:
from Queue import Queue
from zmq.utils.strtypes import bytes, unicode, basestring
class ZMQStream(object):
"""A utility class to register callbacks when a zmq socket sends and receives
For use with zmq.eventloop.ioloop
There are 4 main 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
on_err(callback):
register a callback to be run every time there is an error
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
Two other methods for deactivating the callbacks:
stop_on_recv():
turn off the recv callback
stop_on_send():
turn off the send callback
stop_on_err():
turn off the error callback
All of 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 = None
io_loop = None
poller = None
def __init__(self, socket, io_loop=None):
self.socket = socket
self.io_loop = io_loop or ioloop.IOLoop.instance()
self.poller = zmq.Poller()
self._send_queue = Queue()
self._recv_callback = None
self._send_callback = None
self._close_callback = None
self._errback = None
self._recv_copy = False
self._flushed = False
self._state = zmq.POLLERR
with stack_context.NullContext():
self.io_loop.add_handler(
self.socket, self._handle_events, self._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_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):
"""Disable callback on errors."""
return self.on_err(None)
def on_recv(self, callback, copy=True):
"""Register a callback to be called 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.
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
"""
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)
def on_send(self, callback):
"""Register a callback to be called on each send
There will be two arguments: the message being sent (always a list),
and the return result of socket.send_multipart(msg).
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.
on_send(None) disables recv event polling.
Parameters
----------
callback : callable
callback must take exactly two arguments, which will be
There will be two arguments: 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._send_callback = stack_context.wrap(callback)
def on_err(self, callback):
"""register a callback to be called on POLLERR events
with no arguments.
Parameters
----------
callback : callable
callback will be passed no arguments.
"""
self._errback = stack_context.wrap(callback)
def send(self, msg, flags=0, copy=False, callback=None):
"""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, callback=callback)
def send_multipart(self, msg, flags=0, copy=False, callback=None):
"""Send a multipart message, optionally also register a new callback for sends.
See zmq.socket.send_multipart for details.
"""
# self._check_closed()
self._send_queue.put((msg, flags, copy))
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_unicode(self, u, flags=0, encoding='utf-8', callback=None):
"""Send a unicode message with an encoding.
See zmq.socket.send_unicode for details.
"""
if not isinstance(u, basestring):
raise TypeError("unicode/str objects only")
return self.send(u.encode(encoding), flags=flags, callback=callback)
def send_json(self, obj, flags=0, callback=None):
"""Send json-serialized version of an object.
See zmq.socket.send_json for details.
"""
if jsonapi is None:
raise ImportError('jsonlib{1,2}, json or simplejson library is required.')
else:
msg = jsonapi.dumps(obj)
return self.send(msg, flags=flags, callback=callback)
def send_pyobj(self, obj, flags=0, protocol=-1, callback=None):
"""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)
def _finish_flush(self):
"""callback for unsetting _flushed flag."""
self._flushed = False
def flush(self, flag=zmq.POLLIN|zmq.POLLOUT, limit=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.
:func:`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, 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)
"""
# 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():
return flag & zmq.POLLIN | (self.sending() and flag & zmq.POLLOUT)
self.poller.register(self.socket, update_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 event & zmq.POLLOUT and self.sending():
self._handle_send()
count += 1
self.poller.register(self.socket, update_flag())
events = self.poller.poll(0)
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
dc = ioloop.DelayedCallback(self._finish_flush, 0, self.io_loop)
dc.start()
elif already_flushed:
self._flushed = True
return count
def set_close_callback(self, callback):
"""Call the given callback when the stream is closed."""
self._close_callback = stack_context.wrap(callback)
def close(self):
"""Close this stream."""
if self.socket is not None:
self.io_loop.remove_handler(self.socket)
dc = ioloop.DelayedCallback(self.socket.close, 100, self.io_loop)
dc.start()
self.socket = None
if self._close_callback:
self._run_callback(self._close_callback)
def receiving(self):
"""Returns True if we are currently receiving from the stream."""
return self._recv_callback is not None
def sending(self):
"""Returns True if we are currently sending to the stream."""
return not self._send_queue.empty()
def closed(self):
return self.socket is None
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.
with stack_context.NullContext():
callback(*args, **kwargs)
except:
logging.error("Uncaught exception, closing connection.",
exc_info=True)
# Close the socket on an uncaught exception from a user callback
# (It would eventually get closed when the socket object is
# gc'd, but we don't want to rely on gc happening before we
# run out of file descriptors)
self.close()
# 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."""
# print "handling events"
if not self.socket:
logging.warning("Got events for closed stream %s", fd)
return
# dispatch events:
if events & zmq.POLLERR:
self._handle_error()
return
if events & zmq.POLLIN:
self._handle_recv()
if not self.socket:
return
if events & zmq.POLLOUT:
self._handle_send()
if not self.socket:
return
# rebuild the poll state
state = zmq.POLLERR
if self.receiving():
state |= zmq.POLLIN
if self.sending():
state |= zmq.POLLOUT
if state != self._state:
self._state = state
self.io_loop.update_handler(self.socket, self._state)
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:
e = sys.exc_info()[1]
if e.errno == zmq.EAGAIN:
# state changed since poll event
pass
else:
logging.error("RECV Error: %s"%zmq.strerror(e.errno))
else:
if self._recv_callback:
callback = self._recv_callback
# self._recv_callback = None
self._run_callback(callback, msg)
# self.update_state()
def _handle_send(self):
"""Handle a send event."""
if self._flushed:
return
if not self.sending():
logging.error("Shouldn't have handled a send event")
return
msg = self._send_queue.get()
try:
status = self.socket.send_multipart(*msg)
except zmq.ZMQError:
e = sys.exc_info()[1]
status = e
if self._send_callback:
callback = self._send_callback
self._run_callback(callback, msg, status)
# self.update_state()
def _handle_error(self):
"""Handle a POLLERR event."""
logging.error("handling error..")
if self._errback is not None:
self._errback()
else:
raise zmq.ZMQError()
def _check_closed(self):
if not self.socket:
raise IOError("Stream is closed")
def _add_io_state(self, state):
"""Add io_state to poller."""
if not self._state & state:
self._state = self._state | state
self.io_loop.update_handler(self.socket, self._state)
def _drop_io_state(self, state):
"""Stop poller from watching an io_state."""
if self._state & state:
self._state = self._state & (~state)
self.io_loop.update_handler(self.socket, self._state)
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