Update 6.4.x branch with some missing commits (#6308)

Co-authored-by: GitHub Action <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Vishwajeet <33215443+Vishwajeet0510@users.noreply.github.com>
Co-authored-by: Kevin Bates <kbates4@gmail.com>

CHANGELOG.md

@@ -14,6 +14,22 @@ Use `pip install pip --upgrade` to upgrade pip. Check pip version with
 
 <!-- <START NEW CHANGELOG ENTRY> -->
 
+## 6.4.8
+
+([Full Changelog](https://github.com/jupyter/notebook/compare/v6.4.7...479902d83a691253e0cff8439a33577e82408317))
+
+### Bugs fixed
+
+- Fix to remove potential memory leak on Jupyter Notebooks ZMQChannelHandler code [#6251](https://github.com/jupyter/notebook/pull/6251) ([@Vishwajeet0510](https://github.com/Vishwajeet0510))
+
+### Contributors to this release
+
+([GitHub contributors page for this release](https://github.com/jupyter/notebook/graphs/contributors?from=2022-01-12&to=2022-01-25&type=c))
+
+[@Vishwajeet0510](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3AVishwajeet0510+updated%3A2022-01-12..2022-01-25&type=Issues)
+
+<!-- <END NEW CHANGELOG ENTRY> -->
+
 ## 6.4.7
 
 ([Full Changelog](https://github.com/jupyter/notebook/compare/v6.4.6...b77b5e38b8fa1a20150d7fa4d735dbf1c4f00418))
@@ -40,8 +56,6 @@ Use `pip install pip --upgrade` to upgrade pip. Check pip version with
 
 [@antoinecarme](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3Aantoinecarme+updated%3A2021-11-16..2022-01-12&type=Issues) | [@blink1073](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3Ablink1073+updated%3A2021-11-16..2022-01-12&type=Issues) | [@ccw630](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3Accw630+updated%3A2021-11-16..2022-01-12&type=Issues) | [@kevin-bates](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3Akevin-bates+updated%3A2021-11-16..2022-01-12&type=Issues) | [@LiHua-Official](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3ALiHua-Official+updated%3A2021-11-16..2022-01-12&type=Issues) | [@penguinolog](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3Apenguinolog+updated%3A2021-11-16..2022-01-12&type=Issues) | [@tornaria](https://github.com/search?q=repo%3Ajupyter%2Fnotebook+involves%3Atornaria+updated%3A2021-11-16..2022-01-12&type=Issues)
 
-<!-- <END NEW CHANGELOG ENTRY> -->
-
 ## 6.4.6
 
 ([Full Changelog](https://github.com/jupyter/notebook/compare/v6.4.5...160c27d3c23dafe8b42240571db21b0d5cbae2fe))

notebook/services/kernels/handlers.py

@@ -138,7 +138,7 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
         """Nudge the zmq connections with kernel_info_requests
 
         Returns a Future that will resolve when we have received
-        a shell reply and at least one iopub message,
+        a shell or control reply and at least one iopub message,
         ensuring that zmq subscriptions are established,
         sockets are fully connected, and kernel is responsive.
 
@@ -157,10 +157,12 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
             f = Future()
             f.set_result(None)
             return f
-
         # Use a transient shell channel to prevent leaking
         # shell responses to the front-end.
         shell_channel = kernel.connect_shell()
+        # Use a transient control channel to prevent leaking
+        # control responses to the front-end.
+        control_channel = kernel.connect_control()
         # The IOPub used by the client, whose subscriptions we are verifying.
         iopub_channel = self.channels["iopub"]
 
@@ -183,6 +185,8 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
             iopub_channel.stop_on_recv()
             if not shell_channel.closed():
                 shell_channel.close()
+            if not control_channel.closed():
+                control_channel.close()
 
         # trigger cleanup when both message futures are resolved
         both_done.add_done_callback(cleanup)
@@ -193,6 +197,12 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
                 self.log.debug("Nudge: resolving shell future: %s", self.kernel_id)
                 info_future.set_result(None)
 
+        def on_control_reply(msg):
+            self.log.debug("Nudge: control info reply received: %s", self.kernel_id)
+            if not info_future.done():
+                self.log.debug("Nudge: resolving control future: %s", self.kernel_id)
+                info_future.set_result(None)
+
         def on_iopub(msg):
             self.log.debug("Nudge: IOPub received: %s", self.kernel_id)
             if not iopub_future.done():
@@ -202,6 +212,7 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
 
         iopub_channel.on_recv(on_iopub)
         shell_channel.on_recv(on_shell_reply)
+        control_channel.on_recv(on_control_reply)
         loop = IOLoop.current()
 
         # Nudge the kernel with kernel info requests until we get an IOPub message
@@ -227,6 +238,12 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
 
             # check for closed zmq socket
             if shell_channel.closed():
+                self.log.debug("Nudge: cancelling on closed zmq socket: %s", self.kernel_id)
+                finish()
+                return
+
+            # check for closed zmq socket
+            if control_channel.closed():
                 self.log.debug(
                     "Nudge: cancelling on closed zmq socket: %s", self.kernel_id
                 )
@@ -237,6 +254,7 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
                 log = self.log.warning if count % 10 == 0 else self.log.debug
                 log("Nudge: attempt %s on kernel %s" % (count, self.kernel_id))
                 self.session.send(shell_channel, "kernel_info_request")
+                self.session.send(control_channel, "kernel_info_request")
                 nonlocal nudge_handle
                 nudge_handle = loop.call_later(0.5, nudge, count)
 
@@ -371,7 +389,8 @@ class ZMQChannelsHandler(AuthenticatedZMQStreamHandler):
         if stale_handler:
             self.log.warning("Replacing stale connection: %s", self.session_key)
             yield stale_handler.close()
-        self._open_sessions[self.session_key] = self
+        if self.kernel_id in self.kernel_manager:  # only update open sessions if kernel is actively managed
+            self._open_sessions[self.session_key] = self
 
     def open(self, kernel_id):
         super().open()

notebook/static/base/js/namespace.js

@@ -73,7 +73,7 @@ define(function(){
     // tree
     jglobal('SessionList','tree/js/sessionlist');
 
-    Jupyter.version = "6.4.7";
+    Jupyter.version = "6.4.8";
     Jupyter._target = '_blank';
 
     return Jupyter;