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HOWTO Set up a TLJH server for hosting AstroInteractives

Juan Cabanela (cabanela@mnstate.edu)

To help others who may be scared at the prospect of setting up a JupyterHub Server to allow you to run the AstroInteractives), I have put together this HOWTO guide. As a warning, quite a bit of the software is in active development, so the instructions may be out of date. I'll try to give pointers about where to check for updated instructions when you need them.

We will be using The Littlest JupyterHub, a version of the JuptyerHub server meant for quick installations and relatively small loads. We will abbreviate it throughout this document at TLJH. TLJH currently expects to run on at least Ubuntu 18.04 Linux. Their website has links to documentation for installing it. I will review the installation because I didn't find actually getting it installed tricky.

Install Ubuntu 18.04

We installed Ubuntu on a virtual machine, but the instructions should work similarly for a hardware PC. I will use the term "PC" generically below. We set up the PC with four 2.3 GHz CPUs, 6GB of RAM, and 20GB of hard drive space allocated. This was necessary to run ten of our most CPU intensive interactives at the same time without too much lag. Your set up may need different requirements depending on the expected load.

  1. Boot the PC from 18.04 live server ISO with network card active.
    Follow the instructions in the installer and install Ubuntu using appropriate network and formatting settings for your machine. This will likely be "destructive," wiping out pre-existing data on that PC and using the entire disk for the Ubuntu installation.

  2. Create the admin account, keeping in mind you will install TLJH from this account.

  3. Once you are done, reboot the PC (removing the installation media). Perform all the necessary updates from the admin account command line by doing

     sudo apt-get update
     sudo apt-get upgrade
    
  4. Confirm the necessary python, git, and curl packages are installed by doing:

     sudo apt-get install python3 git curl
    

Install TLJH

Once you have your Ubuntu server, the actual installation of TLJH is performed with a single command from the command line:

  1. Running the installer: You will likely want to look at the TLJH documentation to confirm these instructions are still valid. Assuming they are, you can issue the command (all on one line) in the terminal:

     curl https://raw.githubusercontent.com/jupyterhub/the-littlest-jupyterhub/master/bootstrap/bootstrap.py | sudo -E python3 - --admin <admin-user-name>
    

If everything works, after a few minutes you should see (at the end of a bunch of text output about various items being installed and downloaded) the phrase Done!

  1. Testing the Installation: At this point, you could copy the Public IP of your server, and try accessing http://<public-ip> from your browser. If it worked, you should get a JupyterHub login prompt like the one shown here, including the warning that you want to enable HTTPS so that connections to your server are encrypted. Image of JupyterHub Login

  2. You can enable https using the Let's Encrypt service. However, before you can attempt that you MUST give your server a publicly visible domain name and it can't have its port 80 or 443 blocked by a firewall. Once you are certain that the TLJH server is visible to the outside world, the following commands should allow TLJH to negotiate with Let's Encrypt to get you a proper security certificate and enable encrypted connections to your server (and disable un-encrypted one).

     sudo -E tljh-config set https.enabled true
     sudo -E tljh-config set https.letsencrypt.email <admin_email>
     sudo -E tljh-config add-item https.letsencrypt.domains <DNS_name_of_server>
     sudo -E tljh-config show
     sudo -E tljh-config reload proxy
    

If this fails, just do the following to reenable un-encrypted server connections.

	sudo -E tljh-config set https.enabled true
	sudo -E tljh-config reload proxy

More detailed instructions for enabling encryption are on the TLJH documentation site

Configuring TLJH for AstroInteractives

  1. Setting up JupyterHub accounts: If you point your browsers to https://<public-ip> you can now log in. If you login using the admin user name you used previously, you can choose any password that you wish. Use a strong password & note it down somewhere, since this will be the password for the admin user account from now on.

    • At this point, you can use the JupyterHub interface to set up user accounts. Go to the TLJH server installation instructions and look at Step 2 onward. You will also notice that you can select a terminal from the "New" menu, which opens a terminal in your web browser. You can use this to maintain or update your server at this point, it is almost equivalent to the terminal from the console.
    • WARNING: The default setup is to use FirstUseAuthentication approach to authentication. This means the first time someone enters a new username, the password they enter becomes their JupyterHub password. It creates a system account with username jupyter-<username> and a home directory at /home/jupyter-<username>. The system password on that account is left unset so remote logins are disabled (however, Jupyter offers within it a terminal function, so using this approach means anyone can get user-level terminal access to your server). There are instructions online to change authentication methods to other, more secure means.
  2. Log into the JupyterHub terminal from your admin account: For the remaining terminal commands, you will want to be logged in via the JupyterHub web interface and open up a terminal via the New menu.

  3. Installing the necessary Python Libraries: The next step is to set up the default anaconda environment to include the necessary libraries to run AstroInteractives. From the admin account, open a terminal and from the command line, add ``conda-forge``` as a location to pull python packages from, then install the necessary python packages:

     sudo -E conda config --add channels conda-forge
     sudo -E conda install appmode astropy bqplot pandas matplotlib scipy ipywidgets numpy pythreejs
    
  4. Shut Down Existing Servers: At this point, you will need to shut down any existing JupyterHub server processes (via the web browser admin interface) to make sure these new libraries are available. To do this: Log into your THJH via the web interface

    • Click on the "Control Panel" button in the upper right.
    • Click on the Admin menu item and on that page just "Stop All" servers.
  5. Creating your own copy of AstroInteractives: At this point, I strongly recommend you log into GitHub and fork the AstroInteractives code. This will create a copy of the code in your own repository on GitHub that you can then modify to suit your own needs. To do this:

  6. Installing AstroInteractives in your own account to test it: Then, from your admin account, use the terminal to clone the repository to your account:

     git clone https://github.com/<your_github_account>/AstroInteractives.git
    

Configuring Voila to Share our Installation

When we first set up these servers, we had to then set up indivudal accounts for each student in the class, which was a logistical pain. However, in summer 2019, we hit on a solution by using Voila to publically expose executable Jupyter notebooks. By using voila, we simply point the students to a webpage and they access the interactives directly like any other webapp.

  1. Install Voila: While logged in on the JupyterHub terminal, type
sudo -E conda install -c conda-forge voila

to install voila. After installation, you will need to install the corresponding JupyterHub extension, by typing:

jupyter labextension install @jupyter-voila/jupyterlab-preview
  1. Run Voila: Once we have Voila installed, just cd to the directory where you have the AstroInteractives installed and type:
voila --no-browser

which opens up port 8866 for access to the interactive (NOTE: the default voila session also strips the source from the HTML comments, so students can't see the source code by any means). Have students point their web-browsers to

http://<my_TLJH_server>:8866/voila/render/index.ipynb

and they should see the index page for the interactives. I saved this URL as a shorter bit.ly link and distributed it to students. WARNING: I currently have made no effort to automate the launching of this voila server so if the server goes down, I have to manually relaunch it.

Configuring TLJH for Individual Accounts (We no longer do this!)

Initially, we set up the server to require each student to have an individual account (which we had to set up) and then set up the following process for automatically downloading and executing the notebooks. This was a real hassle in terms of maintenence, so we switched to the method outlined above for sharing an installation publically. However, I am preserving these instructions for posterity.

  1. Killing old processes: Unfortunately, we have discovered that in the current version of TLJH, there is no automatic shutdown of old JupyterHub processes. If students don't explicitly log out, their process sits there and if a few dozen of these processes remain in memory, they can bog down the server and consume resources. Our solution was to add a cronjob using 'sudo crontab -e' to issue a killall -p jupyterhub-singleuser at 8:00am each morning by adding the line

     0 8 * * * killall -p jupyterhub-singleuser
    

to the cronjob list. That has worked for us.

  1. Customizing the interface: If you want to disable the ability for your students to easily access the control panel or terminal, you can copy the custom.css file to the following location on your server: /etc/skel/.jupyter/custom/custom.css Once you have done so, any NEW users will have this custom CSS copied to their account during their first login, disabling those features. This really isn't helpful for security, but it does help prevent students accidentally killing their JupyterHub process.

  2. Setting up Automatic download of notebooks and Automatic launching: At this point, when a user logs in they will just get a blank account. However, TLJH has the nbgitpuller extension installed, which allows you to configure a link to automatically perform a git pull of the latest version of your repository. This will install/update the software to the latest version in the student's account. With some tweaking, we can also take advantage of the appmode* extension we installed so that we can automatically update the software.

    • Use this Binder page to generate the appropriate URL to give your students. It may take a few minutes for the Binder session to launch. Once you see the page which looks like what is shown here. Image of nbgitpuller generator page

    • On that page, fill in the fields:

      • hub_url is the url of your JupyterHub Server
      • repo_url is the url for your GitHub repository
      • filepath is index.ipynb, the name of the index notebook.
      • At this point, you can test the link and see if it has the desired effect of downloading and updating the copy of your GitHub repository.
    • Once you have generated the link, change it as follows to trigger appmode. The link you generated should look like https://<my_TLJH_server>/hub/user-redirect/git-pull?repo=<repo_URL_encoded>&subPath=index.ipynb&app=notebook To automatically trigger appmode, replace subPath=index.ipynb with urlpath=apps/AstroInteractives/index.ipynb so it looks like https://<my_TLJH_server>/hub/user-redirect/git-pull?repo=<repo_URL_encoded>&urlpath=apps/AstroInteractives/index.ipynb&app=notebook Please note that the part between apps and index.ipynb depends on the name of your repo, because by default a git pull creates a directory with the same name as your repository. I assumed you named it AstroInteractives. Finally, I used bit.ly to generate a much shorter URL that I give my students.

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