Backport PR #4513 on branch 5.7.x (Fix regressions in 5.7.x)

docs/source/changelog.rst

@@ -21,6 +21,17 @@ We strongly recommend that you upgrade pip to version 9+ of pip before upgrading
     Use ``pip install pip --upgrade`` to upgrade pip. Check pip version with
     ``pip --version``.
 
+.. _release-5.7.7:
+
+5.7.7
+-----
+
+- Fix regression in restarting kernels in 5.7.5.
+  The restart handler would return before restart was completed.
+- Further improve compatibility with tornado 6 with improved
+  checks for when websockets are closed.
+- Fix regression in 5.7.6 on Windows where .js files could have the wrong mime-type.
+
 .. _release-5.7.6:
 
 5.7.6

notebook/base/zmqhandlers.py

@@ -17,7 +17,8 @@
 
 import tornado
 from tornado import gen, ioloop, web
-from tornado.websocket import WebSocketHandler
+from tornado.iostream import StreamClosedError
+from tornado.websocket import WebSocketHandler, WebSocketClosedError
 
 from jupyter_client.session import Session
 from jupyter_client.jsonutil import date_default, extract_dates
@@ -185,8 +186,13 @@ def send_ping(self):
             self.log.warning("WebSocket ping timeout after %i ms.", since_last_pong)
             self.close()
             return
+        try:
+            self.ping(b'')
+        except (StreamClosedError, WebSocketClosedError):
+            # websocket has been closed, stop pinging
+            self.ping_callback.stop()
+            return
 
-        self.ping(b'')
         self.last_ping = now
 
     def on_pong(self, data):
@@ -246,8 +252,14 @@ def _on_zmq_reply(self, stream, msg_list):
             msg = self._reserialize_reply(msg_list, channel=channel)
         except Exception:
             self.log.critical("Malformed message: %r" % msg_list, exc_info=True)
-        else:
+            return
+
+        try:
             self.write_message(msg, binary=isinstance(msg, bytes))
+        except (StreamClosedError, WebSocketClosedError):
+            self.log.warning("zmq message arrived on closed channel")
+            self.close()
+            return
 
 
 class AuthenticatedZMQStreamHandler(ZMQStreamHandler, IPythonHandler):

notebook/services/kernels/kernelmanager.py

@@ -320,7 +320,8 @@ def on_restart_failed():
         channel.on_recv(on_reply)
         loop = IOLoop.current()
         timeout = loop.add_timeout(loop.time() + self.kernel_info_timeout, on_timeout)
-        raise gen.Return(future)
+        # wait for restart to complete
+        yield future
 
     def notify_connect(self, kernel_id):
         """Notice a new connection to a kernel"""