# coding: utf-8
"""Tornado handlers for WebSocket <-> ZMQ sockets."""
# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.
import os
import json
import struct
import warnings
import sys
try:
from urllib.parse import urlparse # Py 3
except ImportError:
from urlparse import urlparse # Py 2
import tornado
from tornado import gen, ioloop, web
from tornado.websocket import WebSocketHandler
from jupyter_client.session import Session
from jupyter_client.jsonutil import date_default, extract_dates
from ipython_genutils.py3compat import cast_unicode
from .handlers import IPythonHandler
def serialize_binary_message(msg):
"""serialize a message as a binary blob
Header:
4 bytes: number of msg parts (nbufs) as 32b int
4 * nbufs bytes: offset for each buffer as integer as 32b int
Offsets are from the start of the buffer, including the header.
Returns
-------
The message serialized to bytes.
"""
# don't modify msg or buffer list in-place
msg = msg.copy()
buffers = list(msg.pop('buffers'))
if sys.version_info < (3, 4):
buffers = [x.tobytes() for x in buffers]
bmsg = json.dumps(msg, default=date_default).encode('utf8')
buffers.insert(0, bmsg)
nbufs = len(buffers)
offsets = [4 * (nbufs + 1)]
for buf in buffers[:-1]:
offsets.append(offsets[-1] + len(buf))
offsets_buf = struct.pack('!' + 'I' * (nbufs + 1), nbufs, *offsets)
buffers.insert(0, offsets_buf)
return b''.join(buffers)
def deserialize_binary_message(bmsg):
"""deserialize a message from a binary blog
Header:
4 bytes: number of msg parts (nbufs) as 32b int
4 * nbufs bytes: offset for each buffer as integer as 32b int
Offsets are from the start of the buffer, including the header.
Returns
-------
message dictionary
"""
nbufs = struct.unpack('!i', bmsg[:4])[0]
offsets = list(struct.unpack('!' + 'I' * nbufs, bmsg[4:4*(nbufs+1)]))
offsets.append(None)
bufs = []
for start, stop in zip(offsets[:-1], offsets[1:]):
bufs.append(bmsg[start:stop])
msg = json.loads(bufs[0].decode('utf8'))
msg['header'] = extract_dates(msg['header'])
msg['parent_header'] = extract_dates(msg['parent_header'])
msg['buffers'] = bufs[1:]
return msg
# ping interval for keeping websockets alive (30 seconds)
WS_PING_INTERVAL = 30000
class WebSocketMixin(object):
"""Mixin for common websocket options"""
ping_callback = None
last_ping = 0
last_pong = 0
stream = None
@property
def ping_interval(self):
"""The interval for websocket keep-alive pings.
Set ws_ping_interval = 0 to disable pings.
"""
return self.settings.get('ws_ping_interval', WS_PING_INTERVAL)
@property
def ping_timeout(self):
"""If no ping is received in this many milliseconds,
close the websocket connection (VPNs, etc. can fail to cleanly close ws connections).
Default is max of 3 pings or 30 seconds.
"""
return self.settings.get('ws_ping_timeout',
max(3 * self.ping_interval, WS_PING_INTERVAL)
)
def check_origin(self, origin=None):
"""Check Origin == Host or Access-Control-Allow-Origin.
Tornado >= 4 calls this method automatically, raising 403 if it returns False.
"""
if self.allow_origin == '*' or (
hasattr(self, 'skip_check_origin') and self.skip_check_origin()):
return True
host = self.request.headers.get("Host")
if origin is None:
origin = self.get_origin()
# If no origin or host header is provided, assume from script
if origin is None or host is None:
return True
origin = origin.lower()
origin_host = urlparse(origin).netloc
# OK if origin matches host
if origin_host == host:
return True
# Check CORS headers
if self.allow_origin:
allow = self.allow_origin == origin
elif self.allow_origin_pat:
allow = bool(self.allow_origin_pat.match(origin))
else:
# No CORS headers deny the request
allow = False
if not allow:
self.log.warning("Blocking Cross Origin WebSocket Attempt. Origin: %s, Host: %s",
origin, host,
)
return allow
def clear_cookie(self, *args, **kwargs):
"""meaningless for websockets"""
pass
def open(self, *args, **kwargs):
self.log.debug("Opening websocket %s", self.request.path)
# start the pinging
if self.ping_interval > 0:
loop = ioloop.IOLoop.current()
self.last_ping = loop.time() # Remember time of last ping
self.last_pong = self.last_ping
self.ping_callback = ioloop.PeriodicCallback(
self.send_ping, self.ping_interval,
)
self.ping_callback.start()
return super(WebSocketMixin, self).open(*args, **kwargs)
def send_ping(self):
"""send a ping to keep the websocket alive"""
if self.stream.closed() and self.ping_callback is not None:
self.ping_callback.stop()
return
# check for timeout on pong. Make sure that we really have sent a recent ping in
# case the machine with both server and client has been suspended since the last ping.
now = ioloop.IOLoop.current().time()
since_last_pong = 1e3 * (now - self.last_pong)
since_last_ping = 1e3 * (now - self.last_ping)
if since_last_ping < 2*self.ping_interval and since_last_pong > self.ping_timeout:
self.log.warning("WebSocket ping timeout after %i ms.", since_last_pong)
self.close()
return
self.ping(b'')
self.last_ping = now
def on_pong(self, data):
self.last_pong = ioloop.IOLoop.current().time()
class ZMQStreamHandler(WebSocketMixin, WebSocketHandler):
if tornado.version_info < (4,1):
"""Backport send_error from tornado 4.1 to 4.0"""
def send_error(self, *args, **kwargs):
if self.stream is None:
super(WebSocketHandler, self).send_error(*args, **kwargs)
else:
# If we get an uncaught exception during the handshake,
# we have no choice but to abruptly close the connection.
# TODO: for uncaught exceptions after the handshake,
# we can close the connection more gracefully.
self.stream.close()
def _reserialize_reply(self, msg_or_list, channel=None):
"""Reserialize a reply message using JSON.
msg_or_list can be an already-deserialized msg dict or the zmq buffer list.
If it is the zmq list, it will be deserialized with self.session.
This takes the msg list from the ZMQ socket and serializes the result for the websocket.
This method should be used by self._on_zmq_reply to build messages that can
be sent back to the browser.
"""
if isinstance(msg_or_list, dict):
# already unpacked
msg = msg_or_list
else:
idents, msg_list = self.session.feed_identities(msg_or_list)
msg = self.session.deserialize(msg_list)
if channel:
msg['channel'] = channel
if msg['buffers']:
buf = serialize_binary_message(msg)
return buf
else:
smsg = json.dumps(msg, default=date_default)
return cast_unicode(smsg)
def _on_zmq_reply(self, stream, msg_list):
# Sometimes this gets triggered when the on_close method is scheduled in the
# eventloop but hasn't been called.
if self.stream.closed() or stream.closed():
self.log.warning("zmq message arrived on closed channel")
self.close()
return
channel = getattr(stream, 'channel', None)
try:
msg = self._reserialize_reply(msg_list, channel=channel)
except Exception:
self.log.critical("Malformed message: %r" % msg_list, exc_info=True)
else:
self.write_message(msg, binary=isinstance(msg, bytes))
class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
def set_default_headers(self):
"""Undo the set_default_headers in IPythonHandler
which doesn't make sense for websockets
"""
pass
def pre_get(self):
"""Run before finishing the GET request
Extend this method to add logic that should fire before
the websocket finishes completing.
"""
# authenticate the request before opening the websocket
if self.get_current_user() is None:
self.log.warning("Couldn't authenticate WebSocket connection")
raise web.HTTPError(403)
if self.get_argument('session_id', False):
self.session.session = cast_unicode(self.get_argument('session_id'))
else:
self.log.warning("No session ID specified")
@gen.coroutine
def get(self, *args, **kwargs):
# pre_get can be a coroutine in subclasses
# assign and yield in two step to avoid tornado 3 issues
res = self.pre_get()
yield gen.maybe_future(res)
super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs)
def initialize(self):
self.log.debug("Initializing websocket connection %s", self.request.path)
self.session = Session(config=self.config)
def get_compression_options(self):
return self.settings.get('websocket_compression_options', None)