actually send only one kernel_info request

store the Future for the initial request,
allowing subsequent requests to wait on the same pending reply.

Previously, any incoming requests that arrived while waiting for the first reply would send their own request.

IPython/html/services/kernels/handlers.py

@@ -1,294 +1,295 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 gen, web
 from tornado.concurrent import Future
 from tornado.ioloop import IOLoop
 
 from IPython.utils.jsonutil import date_default
 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):
     
     @property
     def kernel_info_timeout(self):
         return self.settings.get('kernel_info_timeout', 10)
     
     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)
     
     def request_kernel_info(self):
         """send a request for kernel_info"""
         km = self.kernel_manager
         kernel = km.get_kernel(self.kernel_id)
         try:
-            # check for cached value
-            kernel_info = kernel._kernel_info
+            # check for previous request
+            future = kernel._kernel_info_future
         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")
+            # store the future on the kernel, so only one request is sent
+            kernel._kernel_info_future = self._kernel_info_future
         else:
-            # use cached value, don't resend request
-            self._finish_kernel_info(kernel_info)
+            if not future.done():
+                self.log.debug("Waiting for pending kernel_info request")
+            future.add_done_callback(lambda f: self._finish_kernel_info(f.result()))
         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._kernel_info_future.set_result(None)
+            self._kernel_info_future.set_result({})
             return
         else:
             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:
-                kernel = self.kernel_manager.get_kernel(self.kernel_id)
-                kernel._kernel_info = 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)
         if not self._kernel_info_future.done():
             self._kernel_info_future.set_result(info)
     
     def initialize(self):
         super(ZMQChannelHandler, self).initialize()
         self.zmq_stream = None
         self.kernel_id = None
         self.kernel_info_channel = None
         self._kernel_info_future = Future()
     
     @gen.coroutine
     def pre_get(self):
         # authenticate first
         super(ZMQChannelHandler, self).pre_get()
         # then request kernel info, waiting up to a certain time before giving up.
         # We don't want to wait forever, because browsers don't take it well when
         # servers never respond to websocket connection requests.
         future = self.request_kernel_info()
         
         def give_up():
             """Don't wait forever for the kernel to reply"""
             if future.done():
                 return
             self.log.warn("Timeout waiting for kernel_info reply from %s", self.kernel_id)
-            future.set_result(None)
+            future.set_result({})
         loop = IOLoop.current()
         loop.add_timeout(loop.time() + self.kernel_info_timeout, give_up)
         # actually wait for it
         yield future
     
     @gen.coroutine
     def get(self, kernel_id):
         self.kernel_id = cast_unicode(kernel_id, 'ascii')
         yield super(ZMQChannelHandler, self).get(kernel_id=kernel_id)
     
     def open(self, kernel_id):
         super(ZMQChannelHandler, self).open()
         try:
             self.create_stream()
         except web.HTTPError as e:
             self.log.error("Error opening stream: %s", e)
             # 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)
 ]