cache kernel_info reply for protocol adaptation

WebSocket connections will not open until kernel_info is retrieved,
removing a race condition waiting for the reply to indicate adaptation,
which could result in a v5 message being sent to a v4 kernel.
The reply is cached, so that it need not be requested on each new connection.

IPython/html/base/zmqhandlers.py

@@ -1,257 +1,256 b''
 """Tornado handlers for WebSocket <-> ZMQ sockets."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import json
 import struct
 
 try:
     from urllib.parse import urlparse # Py 3
 except ImportError:
     from urlparse import urlparse # Py 2
 
 try:
     from http.cookies import SimpleCookie  # Py 3
 except ImportError:
     from Cookie import SimpleCookie  # Py 2
 import logging
 
 import tornado
 from tornado import ioloop
 from tornado import web
 from tornado import websocket
 
 from IPython.kernel.zmq.session import Session
 from IPython.utils.jsonutil import date_default, extract_dates
 from IPython.utils.py3compat import PY3, 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'))
     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
 
 
 class ZMQStreamHandler(websocket.WebSocketHandler):
     
     def check_origin(self, origin):
         """Check Origin == Host or Access-Control-Allow-Origin.
         
         Tornado >= 4 calls this method automatically, raising 403 if it returns False.
         We call it explicitly in `open` on Tornado < 4.
         """
         if self.allow_origin == '*':
             return True
 
         host = self.request.headers.get("Host")
 
         # If no header is provided, assume we can't verify origin
         if origin is None:
             self.log.warn("Missing Origin header, rejecting WebSocket connection.")
             return False
         if host is None:
             self.log.warn("Missing Host header, rejecting WebSocket connection.")
             return False
         
         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.warn("Blocking Cross Origin WebSocket Attempt.  Origin: %s, Host: %s",
                 origin, host,
             )
         return allow
 
     def clear_cookie(self, *args, **kwargs):
         """meaningless for websockets"""
         pass
 
     def _reserialize_reply(self, msg_list):
         """Reserialize a reply message using JSON.
 
         This takes the msg list from the ZMQ socket, deserializes it using
         self.session and then serializes the result using JSON. This method
         should be used by self._on_zmq_reply to build messages that can
         be sent back to the browser.
         """
         idents, msg_list = self.session.feed_identities(msg_list)
         msg = self.session.deserialize(msg_list)
         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, 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(): return
         try:
             msg = self._reserialize_reply(msg_list)
         except Exception:
             self.log.critical("Malformed message: %r" % msg_list, exc_info=True)
         else:
             self.write_message(msg, binary=isinstance(msg, bytes))
 
     def allow_draft76(self):
         """Allow draft 76, until browsers such as Safari update to RFC 6455.
         
         This has been disabled by default in tornado in release 2.2.0, and
         support will be removed in later versions.
         """
         return True
 
 # ping interval for keeping websockets alive (30 seconds)
 WS_PING_INTERVAL = 30000
 
 class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):
     ping_callback = None
     last_ping = 0
     last_pong = 0
     
     @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 set_default_headers(self):
         """Undo the set_default_headers in IPythonHandler
         
         which doesn't make sense for websockets
         """
         pass
     
     def get(self, *args, **kwargs):
         # Check to see that origin matches host directly, including ports
         # Tornado 4 already does CORS checking
         if tornado.version_info[0] < 4:
             if not self.check_origin(self.get_origin()):
                 raise web.HTTPError(403)
         
         # authenticate the request before opening the websocket
         if self.get_current_user() is None:
             self.log.warn("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.warn("No session ID specified")
         
         return super(AuthenticatedZMQStreamHandler, self).get(*args, **kwargs)
     
     def initialize(self):
         self.session = Session(config=self.config)
     
-    def open(self, kernel_id):
-        self.kernel_id = cast_unicode(kernel_id, 'ascii')
+    def open(self, *args, **kwargs):
         
         # start the pinging
         if self.ping_interval > 0:
             self.last_ping = ioloop.IOLoop.instance().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()
 
     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.instance().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.warn("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.instance().time()

IPython/html/services/kernels/handlers.py

@@ -1,233 +1,267 b''
 """Tornado handlers for kernels."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import json
 import logging
-from tornado import web
+from tornado import gen, web
+from tornado.concurrent import Future
 
 from IPython.utils.jsonutil import date_default
-from IPython.utils.py3compat import string_types
+from IPython.utils.py3compat import cast_unicode
 from IPython.html.utils import url_path_join, url_escape
 
 from ...base.handlers import IPythonHandler, json_errors
 from ...base.zmqhandlers import AuthenticatedZMQStreamHandler, deserialize_binary_message
 
 from IPython.core.release import kernel_protocol_version
 
 class MainKernelHandler(IPythonHandler):
 
     @web.authenticated
     @json_errors
     def get(self):
         km = self.kernel_manager
         self.finish(json.dumps(km.list_kernels()))
 
     @web.authenticated
     @json_errors
     def post(self):
         km = self.kernel_manager
         model = self.get_json_body()
         if model is None:
             model = {
                 'name': km.default_kernel_name
             }
         else:
             model.setdefault('name', km.default_kernel_name)
 
         kernel_id = km.start_kernel(kernel_name=model['name'])
         model = km.kernel_model(kernel_id)
         location = url_path_join(self.base_url, 'api', 'kernels', kernel_id)
         self.set_header('Location', url_escape(location))
         self.set_status(201)
         self.finish(json.dumps(model))
 
 
 class KernelHandler(IPythonHandler):
 
     SUPPORTED_METHODS = ('DELETE', 'GET')
 
     @web.authenticated
     @json_errors
     def get(self, kernel_id):
         km = self.kernel_manager
         km._check_kernel_id(kernel_id)
         model = km.kernel_model(kernel_id)
         self.finish(json.dumps(model))
 
     @web.authenticated
     @json_errors
     def delete(self, kernel_id):
         km = self.kernel_manager
         km.shutdown_kernel(kernel_id)
         self.set_status(204)
         self.finish()
 
 
 class KernelActionHandler(IPythonHandler):
 
     @web.authenticated
     @json_errors
     def post(self, kernel_id, action):
         km = self.kernel_manager
         if action == 'interrupt':
             km.interrupt_kernel(kernel_id)
             self.set_status(204)
         if action == 'restart':
             km.restart_kernel(kernel_id)
             model = km.kernel_model(kernel_id)
             self.set_header('Location', '{0}api/kernels/{1}'.format(self.base_url, kernel_id))
             self.write(json.dumps(model))
         self.finish()
 
 
 class ZMQChannelHandler(AuthenticatedZMQStreamHandler):
     
     def __repr__(self):
         return "%s(%s)" % (self.__class__.__name__, getattr(self, 'kernel_id', 'uninitialized'))
     
     def create_stream(self):
         km = self.kernel_manager
         meth = getattr(km, 'connect_%s' % self.channel)
         self.zmq_stream = meth(self.kernel_id, identity=self.session.bsession)
-        # Create a kernel_info channel to query the kernel protocol version.
-        # This channel will be closed after the kernel_info reply is received.
-        self.kernel_info_channel = None
-        self.kernel_info_channel = km.connect_shell(self.kernel_id)
-        self.kernel_info_channel.on_recv(self._handle_kernel_info_reply)
-        self._request_kernel_info()
     
-    def _request_kernel_info(self):
+    def request_kernel_info(self):
         """send a request for kernel_info"""
-        self.log.debug("requesting kernel info")
-        self.session.send(self.kernel_info_channel, "kernel_info_request")
+        km = self.kernel_manager
+        kernel = km.get_kernel(self.kernel_id)
+        try:
+            # check for cached value
+            kernel_info = kernel._kernel_info
+        except AttributeError:
+            self.log.debug("Requesting kernel info from %s", self.kernel_id)
+            # Create a kernel_info channel to query the kernel protocol version.
+            # This channel will be closed after the kernel_info reply is received.
+            if self.kernel_info_channel is None:
+                self.kernel_info_channel = km.connect_shell(self.kernel_id)
+            self.kernel_info_channel.on_recv(self._handle_kernel_info_reply)
+            self.session.send(self.kernel_info_channel, "kernel_info_request")
+        else:
+            # use cached value, don't resend request
+            self._finish_kernel_info(kernel_info)
+        return self._kernel_info_future
     
     def _handle_kernel_info_reply(self, msg):
         """process the kernel_info_reply
         
         enabling msg spec adaptation, if necessary
         """
         idents,msg = self.session.feed_identities(msg)
         try:
             msg = self.session.deserialize(msg)
         except:
             self.log.error("Bad kernel_info reply", exc_info=True)
-            self._request_kernel_info()
+            self.request_kernel_info()
             return
         else:
-            if msg['msg_type'] != 'kernel_info_reply' or 'protocol_version' not in msg['content']:
-                self.log.error("Kernel info request failed, assuming current %s", msg['content'])
+            info = msg['content']
+            self.log.debug("Received kernel info: %s", info)
+            if msg['msg_type'] != 'kernel_info_reply' or 'protocol_version' not in info:
+                self.log.error("Kernel info request failed, assuming current %s", info)
             else:
-                protocol_version = msg['content']['protocol_version']
-                if protocol_version != kernel_protocol_version:
-                    self.session.adapt_version = int(protocol_version.split('.')[0])
-                    self.log.info("adapting kernel to %s" % protocol_version)
-        self.kernel_info_channel.close()
+                kernel = self.kernel_manager.get_kernel(self.kernel_id)
+                kernel._kernel_info = info
+            self._finish_kernel_info(info)
+        
+        # close the kernel_info channel, we don't need it anymore
+        if self.kernel_info_channel:
+            self.kernel_info_channel.close()
         self.kernel_info_channel = None
     
+    def _finish_kernel_info(self, info):
+        """Finish handling kernel_info reply
+        
+        Set up protocol adaptation, if needed,
+        and signal that connection can continue.
+        """
+        protocol_version = info.get('protocol_version', kernel_protocol_version)
+        if protocol_version != kernel_protocol_version:
+            self.session.adapt_version = int(protocol_version.split('.')[0])
+            self.log.info("Kernel %s speaks protocol %s", self.kernel_id, protocol_version)
+        self._kernel_info_future.set_result(info)
+    
     def initialize(self):
         super(ZMQChannelHandler, self).initialize()
         self.zmq_stream = None
+        self.kernel_info_channel = None
+        self._kernel_info_future = Future()
+    
+    @gen.coroutine
+    def get(self, kernel_id):
+        self.kernel_id = cast_unicode(kernel_id, 'ascii')
+        yield self.request_kernel_info()
+        super(ZMQChannelHandler, self).get(kernel_id)
     
     def open(self, kernel_id):
-        super(ZMQChannelHandler, self).open(kernel_id)
+        super(ZMQChannelHandler, self).open()
         try:
             self.create_stream()
         except web.HTTPError:
             # WebSockets don't response to traditional error codes so we
             # close the connection.
             if not self.stream.closed():
                 self.stream.close()
             self.close()
         else:
             self.zmq_stream.on_recv(self._on_zmq_reply)
 
     def on_message(self, msg):
         if self.zmq_stream is None:
             return
         elif self.zmq_stream.closed():
             self.log.info("%s closed, closing websocket.", self)
             self.close()
             return
         if isinstance(msg, bytes):
             msg = deserialize_binary_message(msg)
         else:
             msg = json.loads(msg)
         self.session.send(self.zmq_stream, msg)
 
     def on_close(self):
         # This method can be called twice, once by self.kernel_died and once
         # from the WebSocket close event. If the WebSocket connection is
         # closed before the ZMQ streams are setup, they could be None.
         if self.zmq_stream is not None and not self.zmq_stream.closed():
             self.zmq_stream.on_recv(None)
             # close the socket directly, don't wait for the stream
             socket = self.zmq_stream.socket
             self.zmq_stream.close()
             socket.close()
 
 
 class IOPubHandler(ZMQChannelHandler):
     channel = 'iopub'
     
     def create_stream(self):
         super(IOPubHandler, self).create_stream()
         km = self.kernel_manager
         km.add_restart_callback(self.kernel_id, self.on_kernel_restarted)
         km.add_restart_callback(self.kernel_id, self.on_restart_failed, 'dead')
     
     def on_close(self):
         km = self.kernel_manager
         if self.kernel_id in km:
             km.remove_restart_callback(
                 self.kernel_id, self.on_kernel_restarted,
             )
             km.remove_restart_callback(
                 self.kernel_id, self.on_restart_failed, 'dead',
             )
         super(IOPubHandler, self).on_close()
     
     def _send_status_message(self, status):
         msg = self.session.msg("status",
             {'execution_state': status}
         )
         self.write_message(json.dumps(msg, default=date_default))
 
     def on_kernel_restarted(self):
         logging.warn("kernel %s restarted", self.kernel_id)
         self._send_status_message('restarting')
 
     def on_restart_failed(self):
         logging.error("kernel %s restarted failed!", self.kernel_id)
         self._send_status_message('dead')
     
     def on_message(self, msg):
         """IOPub messages make no sense"""
         pass
 
 
 class ShellHandler(ZMQChannelHandler):
     channel = 'shell'
 
 
 class StdinHandler(ZMQChannelHandler):
     channel = 'stdin'
 
 
 #-----------------------------------------------------------------------------
 # URL to handler mappings
 #-----------------------------------------------------------------------------
 
 
 _kernel_id_regex = r"(?P<kernel_id>\w+-\w+-\w+-\w+-\w+)"
 _kernel_action_regex = r"(?P<action>restart|interrupt)"
 
 default_handlers = [
     (r"/api/kernels", MainKernelHandler),
     (r"/api/kernels/%s" % _kernel_id_regex, KernelHandler),
     (r"/api/kernels/%s/%s" % (_kernel_id_regex, _kernel_action_regex), KernelActionHandler),
     (r"/api/kernels/%s/iopub" % _kernel_id_regex, IOPubHandler),
     (r"/api/kernels/%s/shell" % _kernel_id_regex, ShellHandler),
     (r"/api/kernels/%s/stdin" % _kernel_id_regex, StdinHandler)
 ]