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# coding: utf-8
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"""Tornado handlers for WebSocket <-> ZMQ sockets."""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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import json
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import struct
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try:
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from urllib.parse import urlparse # Py 3
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except ImportError:
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from urlparse import urlparse # Py 2
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import tornado
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from tornado import gen, ioloop, web, websocket
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from IPython.kernel.zmq.session import Session
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from IPython.utils.jsonutil import date_default, extract_dates
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from IPython.utils.py3compat import cast_unicode
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from .handlers import IPythonHandler
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def serialize_binary_message(msg):
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"""serialize a message as a binary blob
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Header:
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4 bytes: number of msg parts (nbufs) as 32b int
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4 * nbufs bytes: offset for each buffer as integer as 32b int
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Offsets are from the start of the buffer, including the header.
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Returns
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-------
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The message serialized to bytes.
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"""
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# don't modify msg or buffer list in-place
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msg = msg.copy()
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buffers = list(msg.pop('buffers'))
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bmsg = json.dumps(msg, default=date_default).encode('utf8')
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buffers.insert(0, bmsg)
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nbufs = len(buffers)
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offsets = [4 * (nbufs + 1)]
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for buf in buffers[:-1]:
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offsets.append(offsets[-1] + len(buf))
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offsets_buf = struct.pack('!' + 'I' * (nbufs + 1), nbufs, *offsets)
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buffers.insert(0, offsets_buf)
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return b''.join(buffers)
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def deserialize_binary_message(bmsg):
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"""deserialize a message from a binary blog
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Header:
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4 bytes: number of msg parts (nbufs) as 32b int
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4 * nbufs bytes: offset for each buffer as integer as 32b int
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Offsets are from the start of the buffer, including the header.
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Returns
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-------
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message dictionary
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"""
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nbufs = struct.unpack('!i', bmsg[:4])[0]
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offsets = list(struct.unpack('!' + 'I' * nbufs, bmsg[4:4*(nbufs+1)]))
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offsets.append(None)
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bufs = []
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for start, stop in zip(offsets[:-1], offsets[1:]):
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bufs.append(bmsg[start:stop])
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msg = json.loads(bufs[0].decode('utf8'))
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msg['header'] = extract_dates(msg['header'])
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msg['parent_header'] = extract_dates(msg['parent_header'])
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msg['buffers'] = bufs[1:]
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return msg
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class ZMQStreamHandler(websocket.WebSocketHandler):
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def check_origin(self, origin):
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"""Check Origin == Host or Access-Control-Allow-Origin.
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Tornado >= 4 calls this method automatically, raising 403 if it returns False.
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We call it explicitly in `open` on Tornado < 4.
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"""
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if self.allow_origin == '*':
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return True
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host = self.request.headers.get("Host")
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# If no header is provided, assume we can't verify origin
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if origin is None:
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self.log.warn("Missing Origin header, rejecting WebSocket connection.")
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return False
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if host is None:
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self.log.warn("Missing Host header, rejecting WebSocket connection.")
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return False
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origin = origin.lower()
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origin_host = urlparse(origin).netloc
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# OK if origin matches host
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if origin_host == host:
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return True
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# Check CORS headers
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if self.allow_origin:
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allow = self.allow_origin == origin
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elif self.allow_origin_pat:
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allow = bool(self.allow_origin_pat.match(origin))
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else:
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# No CORS headers deny the request
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allow = False
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if not allow:
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self.log.warn("Blocking Cross Origin WebSocket Attempt. Origin: %s, Host: %s",
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origin, host,
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)
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return allow
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def clear_cookie(self, *args, **kwargs):
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"""meaningless for websockets"""
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pass
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def _reserialize_reply(self, msg_list):
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"""Reserialize a reply message using JSON.
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This takes the msg list from the ZMQ socket, deserializes it using
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self.session and then serializes the result using JSON. This method
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should be used by self._on_zmq_reply to build messages that can
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be sent back to the browser.
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"""
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idents, msg_list = self.session.feed_identities(msg_list)
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msg = self.session.deserialize(msg_list)
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if msg['buffers']:
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buf = serialize_binary_message(msg)
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return buf
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else:
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smsg = json.dumps(msg, default=date_default)
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return cast_unicode(smsg)
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def _on_zmq_reply(self, msg_list):
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# Sometimes this gets triggered when the on_close method is scheduled in the
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# eventloop but hasn't been called.
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if self.stream.closed(): return
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try:
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msg = self._reserialize_reply(msg_list)
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except Exception:
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self.log.critical("Malformed message: %r" % msg_list, exc_info=True)
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else:
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self.write_message(msg, binary=isinstance(msg, bytes))
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def allow_draft76(self):
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"""Allow draft 76, until browsers such as Safari update to RFC 6455.
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This has been disabled by default in tornado in release 2.2.0, and
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support will be removed in later versions.
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"""
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return True
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# ping interval for keeping websockets alive (30 seconds)
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WS_PING_INTERVAL = 30000
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class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
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ping_callback = None
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last_ping = 0
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last_pong = 0
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@property
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def ping_interval(self):
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"""The interval for websocket keep-alive pings.
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Set ws_ping_interval = 0 to disable pings.
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"""
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return self.settings.get('ws_ping_interval', WS_PING_INTERVAL)
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@property
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def ping_timeout(self):
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"""If no ping is received in this many milliseconds,
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close the websocket connection (VPNs, etc. can fail to cleanly close ws connections).
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Default is max of 3 pings or 30 seconds.
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"""
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return self.settings.get('ws_ping_timeout',
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max(3 * self.ping_interval, WS_PING_INTERVAL)
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)
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def set_default_headers(self):
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"""Undo the set_default_headers in IPythonHandler
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which doesn't make sense for websockets
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"""
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pass
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def pre_get(self):
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"""Run before finishing the GET request
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Extend this method to add logic that should fire before
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the websocket finishes completing.
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"""
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# Check to see that origin matches host directly, including ports
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# Tornado 4 already does CORS checking
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if tornado.version_info[0] < 4:
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if not self.check_origin(self.get_origin()):
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raise web.HTTPError(403)
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# authenticate the request before opening the websocket
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if self.get_current_user() is None:
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self.log.warn("Couldn't authenticate WebSocket connection")
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raise web.HTTPError(403)
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if self.get_argument('session_id', False):
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self.session.session = cast_unicode(self.get_argument('session_id'))
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else:
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self.log.warn("No session ID specified")
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@gen.coroutine
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def get(self, *args, **kwargs):
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# pre_get can be a coroutine in subclasses
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yield gen.maybe_future(self.pre_get())
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# FIXME: only do super get on tornado ≥ 4
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# tornado 3 has no get, will raise 405
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if tornado.version_info >= (4,):
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super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs)
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def initialize(self):
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self.log.debug("Initializing websocket connection %s", self.request.path)
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self.session = Session(config=self.config)
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def open(self, *args, **kwargs):
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self.log.debug("Opening websocket %s", self.request.path)
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if tornado.version_info < (4,):
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try:
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self.get(*self.open_args, **self.open_kwargs)
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except web.HTTPError:
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self.close()
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raise
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# start the pinging
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if self.ping_interval > 0:
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self.last_ping = ioloop.IOLoop.instance().time() # Remember time of last ping
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self.last_pong = self.last_ping
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self.ping_callback = ioloop.PeriodicCallback(self.send_ping, self.ping_interval)
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self.ping_callback.start()
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def send_ping(self):
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"""send a ping to keep the websocket alive"""
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if self.stream.closed() and self.ping_callback is not None:
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self.ping_callback.stop()
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return
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# check for timeout on pong. Make sure that we really have sent a recent ping in
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# case the machine with both server and client has been suspended since the last ping.
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now = ioloop.IOLoop.instance().time()
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since_last_pong = 1e3 * (now - self.last_pong)
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since_last_ping = 1e3 * (now - self.last_ping)
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if since_last_ping < 2*self.ping_interval and since_last_pong > self.ping_timeout:
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self.log.warn("WebSocket ping timeout after %i ms.", since_last_pong)
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self.close()
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return
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self.ping(b'')
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self.last_ping = now
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def on_pong(self, data):
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self.last_pong = ioloop.IOLoop.instance().time()
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