Accessing multiple hosted applications in one Workspace session


For security reasons, Domino Workspace sessions are only accessible on one port. For example, Jupyter typically uses port 8888. When you launch a Jupyter Workspace session, a Domino executor starts the Jupyter server in a Run, and opens port 8888 to serve the Jupyter application to your browser. If you were to attempt to use the Jupyter terminal to start another application on a different port, it would not be accessible.

However, in some cases you may want to run multiple interactive applications in the same Workspace session. These cases include:

  • Editing and debugging Dash or Flask apps live

  • Using Tensorboard to view progress of a live training job

Domino 3.5+ supports this with Jupyter Server Proxy and JupyterLab


  • Python 3+

  • Jupyter Server Proxy

Jupyter Server Proxy is installed by default in the latest Domino Standard Environments. To install it in one of your existing environments, see the instructions below.

Installing Jupyter Server Proxy in your environment

If you are not on the recent version of the Domino Standard Environment, you can install Jupyter Server Proxy in your Domino Environment by following these steps.

Add the following lines to your environment’s Dockerfile Instructions.

USER root

# Install NodeJS
# You can omit this step if your environment already has NodeJS installed
RUN curl -sL | bash - && \
   apt-get install nodejs -y && \
   rm -rf /var/lib/apt/lists/*

# Install jupyterlab-server-proxy (omit if already installed)
RUN if [ -x /opt/conda/bin/conda ]; then \
      /opt/conda/bin/conda install -y -c conda-forge jupyter-server-proxy; \
   else \
      pip install --no-cache-dir jupyter-server-proxy; \

# Update jupyter lab config
RUN mkdir -p home/ubuntu/.jupyterlab/ && \
   echo "c.ServerProxy.servers = {" >> home/ubuntu/.jupyterlab/ && \
   echo "    'code': {" >> home/ubuntu/.jupyterlab/ && \
   # Vscode example. Replace this command with what you want to proxy to
   echo "        'command': ['code-server', '--port', '{port}', '--auth', 'none']" >> /home/ubuntu/.jupyterlab/ && \
   echo "    }" >> /home/ubuntu/.jupyterlab/ && \
   echo "}" >> /home/ubuntu/.jupyterlab/

USER ubuntu

Using Jupyter Server Proxy

If you launch a JupyterLab Workspace session in an environment with Jupyter Server Proxy installed, you can start and serve additional applications as long as they are served on a different port than JupyterLab itself.

By defining a new entry in the jupyter lab config (as done in the previous section), you can add a new tile to your jupyterlab launcher page.


Add the following to your JupyterLab config, which lives at /home/ubuntu/.jupyterlab/

c.ServerProxy.servers = {
   'VSCode': {
      'command': ['code-server', '--port', '{port}']

Be sure to use {port} for the port you want to serve this new application from. After updating the JupyerLab config you will see a new tile under Notebook when you run start your workspace.


Clicking this new tile will open a new window running the specified command. With this model you can host multiple applications on different ports and expose each through your JupyerLab workspace.

Once your app is running, if you edit its source files in JupyterLab, when you restart the app in your browser the edits will take effect.

For environments that have VSCode installed within JupyterLab, it’s possible to start a VSCode session from JupyterLab, and then start an App from VSCode. This will allow you to debug using VSCode.

Note that any new App or process you start and open in a separate tab will not have the Domino Workspace UI, with options to stop, sync, commit, or manage your project files. To access this UI and manage your changes, you must open the main JupyterLab tab for your Workspace session.