This is What I Keep Trying to Say…

Small pieces loosely joined…

Last week, I learned that students on a level 3 course were being asked to install Docker so that they could run a particular application (Genie, a climate simulation tool) distributed via a Docker container image.

RESULT :-)

Two things follow from this:

  1. with Docker installed, giving students access to additional software applications also packaged as Docker containers becomes trivial: just tell them to run a different Docker container;
  2. we can start to join small pieces together in more integrated environments.

Here’s an example of joining pieces together:

There are a couple of tricks involved here.

Trick the first is to use the Genie container image distributed to students as the first part of a Docker multistage build. The useful part of the container distributed to students essentially boils down to three parts:

  1. a built application in a specified directory;
  2. a node.js run time to run the application;
  3. a start command to start the application server.

In a multistage build, I can:

  • pull in the original application container;
  • reset the base layer of the container to a base layer from which *I* want to build (for example, a branded notebook server image);
  • copy over the application files from the original application server container into my container;
  • install a node.js runtime required to run the copied application;
  • install nbserverproxy`jupyter-server-proxy`;
  • create a simple server proxy config file to run the application.

Here’s what the Dockerfile for such a multistage build looks like:

#Demo - multistage build

#From a genie application container
#copy the application into an OU customised notebook container
#and use nbserverproxy to run the genie application

FROM $GENIE_APP
# This loads in the original GEnie application image
# that can run on it's own to serve the Genie app

#But we can also copy the application from that image
# into another container...

FROM ousefulcoursecontainers/oubrandednotebook
#Alternatively, use a notebook container seeded with notebooks

#Install node
USER root
RUN apt update \
&& apt-get install -y curl \
&& curl -sL https://deb.nodesource.com/setup_8.x | bash - \
&& apt-get install -y nodejs

USER $NB_USER

WORKDIR $HOME

#Grab the application files from the originally distributed container
COPY --from=0 /home/genie/node_app ./genie/

#Server proxify the application
RUN pip install --no-cache jupyter-server-proxy
RUN mkdir -p $HOME/.jupyter/
ADD jupyter_notebook_config.py $HOME/.jupyter/

Trick the second is in using juputer-server-proxy (e.g. OpenRefine Running in MyBinder, Several Ways…). This allows you to add a start command to the Jupyter notebook New menu and launch a URL proxied application from it.

nbGenie_png

For completeness, the proxy server config is quite straightforward:

# Traitlet configuration file for jupyter-notebook.
#jupyter_notebook_config.py

c.ServerProxy.servers = {
  'Genie': {
    'command': ['node', 'genie/genie_app.js'],
    'port': 3000,
    'timeout': 120,
    'launcher_entry': {
    'title': 'Genie'
    },
  },
}

Rather than just ship the application container, we can ship the application container in a more general “student workbench” context such as the above. Rather than tell the students to run the original application container, we can get them to launch a more general course environment. This is no harder to do — the blockers and hard work required to install in the Docker environment to run the original application container have already been negotiated. The playing field is now wide open to getting arbitrary applications onto student desktops once Docker is installed.

In the above example, I took the liberty of reworking one of the optional course activities as a Juptyer notebook. The original Word file was a simple derivation of the logistic equation (I seem to have oopsed the filename… doh!), but it wasn’t hard to make a simple interactive around that:

If students have the means to access the interactive environment to hand, we might as well use it if it helps support their learning, right?

Poking around the student forums (keeping an eye out for emerging support issues), I noticed one student referring to an issue with another piece of course software. That particular application was a Java application, and required students to install Java on their computer to run the application.

Hmm… so… students have Docker, we can run Java in a Docker, so why should students have to clutter their computer with a Java install? (Note that the release of the docker application has actually appeared for the first time late in the course presentation, so it wasn’t available at the start of the course. I’m not criticising any of the module production team here, just pointing out a little of what’s possible to try to smooth things for students in the next presentation of the course.)

Is there a workaround?

One of the other small pieces I’ve been exploring is how to expose desktops to students. As posted previously, we can do this via a browser using XPRA or we can use RDP.

So suppose we also get students to download and install the cross-platform Microsoft RDP client.

I can download the Java application files from the VLE, and build my own containerised runner for it using a simple Dockerfile like this:

#Grab an XRDP base container
FROM danielguerra/ubuntu-xrdp

#Install Java runtime
RUN apt-get update && apt-get install -y default-jre && apt-get clean

#Make a directory for the app and copy the application files over
RUN mkdir -p /S397/daisyworld
COPY daisy_1/ /S397/daisyworld/

#Optionally create a directory that we can mount onto from the desktop
#so we can share files in from the desktop if we want to.
RUN mkdir -p /S397/share

In case you’re wondering, when folk say: “everyone should learn to code”, I’d say being able to come up with something like that Dockerfile counts as being able to code.

We can now build and run that container, push it to Dockerhub, and again let students run it with a single docker command (possibly hidden in a shortcut, or maybe launched more simply via Kitematic or docker-compose).

docker run --rm -d --name daisyworld --hostname OU-S397 --shm-size 1g -p 3399:3389 --volume ~/S397/daisyshare:/S397/share $DAISYWORLDCONTAINER

I can now create a remote desktop onto that connection:

login with a default username, and launch the application via the remote desktop:

With a bit of fettling, I wonder if I could customise the desktop a little and perhaps autolaunch the application? Or even, rather then expose the whole desktop, autorun the application and automatically run it full window? (I think way back when I explored a small amount of Linux desktop customisation in a VM here?)

Yes, this is at the overhead of running Java in a container, but it also means we don’t require students to install Java and the application itself.

Next on my to do list is a simple notebook container that bundles XPRA so that we can run desktops over http via jupyter-server-proxy. (CoCalc can do this already… Does anyone have a working Jupyter demo that implements something similar?) With that in place, we could ship a single container that would allow students to run notebooks, the Genie web UI application, and the DaisyWorld Java application via a browser viewable desktop from a single container and via a single UI.

That’s the sort of thing I keep trying to talk about…

That’s why we should be doing this…

PS for Docker on the student desktop, students could equally be accessing the browser based services from docker containers running in the cloud, either on institutionally hosted servers or self-service servers. Running your own docker container instances in the cloud is not difficult: Running a Minimal OU Customised Personal Jupyter Notebook Server on Digital Ocean.

Author: Tony Hirst

I'm a Senior Lecturer at The Open University, with an interest in #opendata policy and practice, as well as general web tinkering...

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