Fixes Jupyter server kernel communication issue when started with explicit IP address.

Author: rashedmyt

src/jupyter_matlab_kernel/kernel.py

@@ -10,11 +10,12 @@
 import ipykernel.kernelbase
 import psutil
 import requests
-from jupyter_matlab_kernel import mwi_comm_helpers, mwi_logger
 from matlab_proxy import settings as mwi_settings
 from matlab_proxy import util as mwi_util
 from requests.exceptions import HTTPError
 
+from jupyter_matlab_kernel import mwi_comm_helpers, mwi_logger
+
 _MATLAB_STARTUP_TIMEOUT = mwi_settings.get_process_startup_timeout()
 _logger = mwi_logger.get()
 
@@ -195,10 +196,13 @@ def start_matlab_proxy(logger=_logger):
             """
         )
 
-    url = "{protocol}://localhost:{port}{base_url}matlab".format(
-        protocol="https" if nb_server["secure"] else "http",
-        port=nb_server["port"],
-        base_url=nb_server["base_url"],
+    # Using nb_server["url"] to construct matlab-proxy URL as it handles the following cases
+    # 1. For normal usage of Jupyter, the URL returned by nb_server uses localhost
+    # 2. For explicitly specified IP with Jupyter, the URL returned by nb_server
+    #       a. uses FQDN hostname when specified IP is 0.0.0.0
+    #       b. uses specified IP for all other cases
+    matlab_proxy_url = "{jupyter_server_url}matlab".format(
+        jupyter_server_url=nb_server["url"]
     )
 
     available_tokens = {
@@ -213,11 +217,11 @@ def start_matlab_proxy(logger=_logger):
         else:
             headers = None
 
-        if _start_matlab_proxy_using_jupyter(url, headers, logger):
+        if _start_matlab_proxy_using_jupyter(matlab_proxy_url, headers, logger):
             logger.debug(
-                f"Started matlab-proxy using jupyter at {url} with headers: {headers}"
+                f"Started matlab-proxy using jupyter at {matlab_proxy_url} with headers: {headers}"
             )
-            return url, nb_server["base_url"], headers
+            return matlab_proxy_url, nb_server["base_url"], headers
 
     logger.error(
         f"MATLABKernel could not communicate with matlab-proxy through Jupyter server"

tests/unit/jupyter_matlab_kernel/mocks/mock_jupyter_server.py

@@ -1,25 +1,27 @@
-# Copyright 2023 The MathWorks, Inc.
+# Copyright 2023-2024 The MathWorks, Inc.
 """Mocks matlab-proxy integration with Jupyter Server.
 
 This module provides a pytest fixture that mocks how matlab-proxy integrates
 with Jupyter server.
 """
 
-
 import os
 
 import pytest
 import requests
 from jupyter_server import serverapp
 
 PID = "server 1"
-PORT = "1234/"
-BASE_URL = "server_of_nb/"
+PORT = "1234"
+BASE_URL = "/server_of_nb/"
 SECURE = False
 TEST_TOKEN = "test_token"
 LICENSING = True
 AUTHORIZED_HEADERS = {"Authorization": "token test_token"}
 PASSWORD = ""
+HOSTNAME = "localhost"
+URL = f"http://{HOSTNAME}:{PORT}{BASE_URL}"
+SECURE_URL = f"https://{HOSTNAME}:{PORT}{BASE_URL}"
 
 
 @pytest.fixture
@@ -42,6 +44,8 @@ def fake_list_running_servers(*args, **kwargs):
                 "secure": SECURE,
                 "token": TEST_TOKEN,
                 "password": PASSWORD,
+                "hostname": HOSTNAME,
+                "url": URL,
             }
         ]
 

tests/unit/jupyter_matlab_kernel/test_kernel.py

@@ -1,13 +1,12 @@
-# Copyright 2023 The MathWorks, Inc.
+# Copyright 2023-2024 The MathWorks, Inc.
 
 # This file contains tests for jupyter_matlab_kernel.kernel
 import mocks.mock_jupyter_server as MockJupyterServer
 import pytest
+from jupyter_matlab_kernel.kernel import MATLABConnectionError, start_matlab_proxy
 from jupyter_server import serverapp
 from mocks.mock_jupyter_server import MockJupyterServerFixture
 
-from jupyter_matlab_kernel.kernel import MATLABConnectionError, start_matlab_proxy
-
 
 def test_start_matlab_proxy_without_jupyter_server():
     """
@@ -55,6 +54,8 @@ def fake_list_running_servers(*args, **kwargs):
                 "secure": True,
                 "token": MockJupyterServer.TEST_TOKEN,
                 "password": MockJupyterServer.PASSWORD,
+                "hostname": MockJupyterServer.HOSTNAME,
+                "url": MockJupyterServer.SECURE_URL,
             }
         ]