berk-parsons

A flask app for easily running experiments with Parsons Problems and common computer science interfaces.

Virtual Environment

It is strongly encouraged to use a virtual environment, such as virtualenv or conda for development. The steps below are for virtualenv:

1. virtualenv env
2. source env/bin/activate

After setting up the virtual environment, download the necessary libraries:

pip install -r requirements.txt

One-time set-up

The below steps only need to be done once when you first download the application.

1. Install Postgres locally with brew install psql
2. In your Terminal, run createdb parsons
3. At the root directory of this repo, run python and the following commands:

>>> from app import db
>>> db.create_all()
>>> exit()

Usage

1. Set your local environment for development by running export FLASK_ENV=development
2. Start Flask server by running python3 parsons.py

// If also starting the autograder, run the following:

3. Start Redis server using redis-server
4. Start grader worker using python3 grader_worker.py

Seeing the First Problem

// Note: Your port number may vary

1. Go to localhost:5000/login
2. Create a user with any username
3. Go to localhost:5000/sigcse-demo

Common Issues

pip install -r requirements.txt raises Failed building wheel for mysqlclient

Try running xcode-select --install in the terminal.

pip install -r requirements.txt raises ld: library not found for -lssl

Try running the following in the terminal:

$ export LDFLAGS="-L/usr/local/opt/openssl/lib"
$ export CPPFLAGS="-I/usr/local/opt/openssl/include"

redis-server raises command not found

Try running brew install redis and then try again.

Contributing

Problem configuration

All problems are configured in YAML files

Rough architecture

• app/ contains the bulk of the application logic. This is responsible for defining routes, specifying problem sequences, rendering problems, and generally handling requests from the user.
• grader/ is a separate surver, used to execute student Python code in a (relatively) safe way. It primarily runs code on test cases and returns results in a consistent format. It connects with the main server through rq, a redis queue library.

Deploying to Flask

The code currently assumes a Postgres database, which Flask will automatically configure to DATABASE_URL.

HIDE_TIMER can be configured at the environment level to fully disable the timer in the upper right for all students.

We have currently set WEB_CONCURRENCY to 8 with standard dynos.

Acknowledgements

• brianhsu98
• srujayk
• alexiacamacho