PrairieLearn Haskell Docker Image

This is a (minor) modification of Mattox Beckman's Docker Image for Haskell auto-grading in PrairieLearn.

Most of what is here is specifically for constructing the Docker image. However, the subfolder haskell-grader is intended to be placed under your PrairieLearn course's serverFilesCourse folder to be used as the external grader system for a course. Documentation on how to use it is in haskell-grader/README.md.

Quick Guide to Setting Up the Docker Image

Ensure that Dockerfile lists the LTS version you want to use in your questions. These need to match to avoid timeouts during student submissions.

To be safe, also update dummy-project-for-stack-caching/stack.yaml with the same LTS version.

Next, update dummy-project-for-stack-caching/package.yaml to add any modules you want Haskell / Stack to have access to to the dependencies list.

Finally, set up the Docker repository you want to push to on Docker Hub. We assume below that it is named haskell-prairielearn under your Docker ID.

If this is set up correctly, you can then run:

docker build . -t <your-docker-id>/haskell-prairielearn:latest
docker push <your-docker-id>/haskell-prairielearn:latest

You can run this with ./redeploy.sh <your-docker-id> (or set your ID as the default in that file and just run ./redeploy.sh).

Configuring the Haskell Autograder

To set up the Haskell Autograder, you'll want to start by understanding autograders in PrairieLearn. Crucially, you'll need two pieces to get started:

1. A Docker image in which to run the autograder.
2. The autograder program itself (and associated questions!).

The Docker Image

You will want to set up your docker image and share it somewhere easy to access it (or use Mattox's at https://hub.docker.com/r/mattox/haskell-prairielearn or Steve's at https://hub.docker.com/r/cswolf/haskell-prairielearn.

Among other things you may want to customize is the LTS version. That's the line like ENV LTS=lts-17.9 in the Dockerfile. Ensure this is the same as the LTS version used in your questions. To decide which version you'll use, you may want to check the Stackage server for correspondence with GHC version. To be safe, ensure that dummy-project-for-stack-caching/stack.yaml refers to the same LTS version.

Additionally, configure the dummy-project-for-stack-caching/package.yaml file to ensure that the docker image, when built, will download and cache everything needed for builds for your questions over the term or students' submissions will timeout. (This isn't too hard to update between major assessments.)

Building and pushing the Docker image

If you're using someone else's docker image, you can skip this step entirely... but you also couldn't have done various of the basic docker configuration above.

If you are making your own docker image:

• Make yourself an account on Docker Hub. Create a public repository there. We'll assume it is named haskell-prairielearn. (For its full name, it will be prefaced by your docker ID.)

• Once you have everything configured for your Docker image (above), go into its directory and run the following (replacing <your-docker-id> with your actual docker ID, like cswolf or mattox):

  docker build . -t <your-docker-id>/haskell-prairielearn:latest

  That will likely take a long time, particularly the stack test stage (which installs all the desired Haskell packages).

• Push your docker image to the hub:

  docker push <your-docker-id>/haskell-prairielearn:latest

Congrats! You now have a Docker image you can reference in PrairieLearn to set up your external autograder! (Caution: PrairieLearn's sync page has a button you need to press manually to actually pull the Docker image for use the first time you use it!)

The Autograder

PrairieLearn makes it easy for your autograder to live in your course under the serverFilesCourse, which gives you some customizability within the constraints of the Docker image.

Details on the autograder are in haskell-grader/README.md.