EduHeLx Grader API

A microservice supporting student submissions to otter grader within EduHeLx

Usage

Installation

You'll need to have installed libpq (Postgres client) first before installing psycopg2 (Postgres driver).

# Setup virtual environment
python3 -m venv venv
source venv/bin/activate

# Install requirements
pip install -r requirements.txt

# Setup .env
cp .env.sample .env
vim .env

Running

set -a && source .env
python -m app.main
# or
uvicorn --reload app.main:app --log-level=info

Documentation

The OpenAPI UI is accessible under /docs. To login, first use the login endpoint to get access/refresh tokens. Then, under Authorize (lock icon), set the value to Bearer {access_token}.

Application Startup

Our application startup is handled by the start.py script. This script performs different actions depending on whether it's running inside a Kubernetes cluster or in a Docker container.

When running in Kubernetes, we assume that a ConfigMap and a Secret are mounted at /etc/grader-config and /etc/grader-secret respectively. These contain the non-sensitive and sensitive configuration parameters for our application. The start.py script will combine the values from these two sources into a single .env file at /app/.env, which is then used by our application for its configuration.

When running in Docker, we expect the .env file to be provided directly. The start.py script checks for the existence of this file and if it exists, it tries to load the environment variables using python-dotenv.

After the .env file has been created or checked, the start.py script starts the application using the Uvicorn ASGI server.

Password Secret Generator

The password secret generator is a Python script that generates a random 12-character alphanumeric password and creates a Kubernetes Secret with this password. The name of the Secret is grader-postgresql.

Before creating the Secret, the script checks if a Secret with this name already exists. If it does, the script prints a message and does not create a new Secret. This prevents accidental overwriting of existing Secrets.

The generated password is used for the PostgreSQL database that our application connects to. It's important to handle this password securely, as it provides access to the database.

Alembic Migrations with Environment Variable Based Configuration

This approach uses Alembic for database migrations in a Python project. Alembic configurations are set based on environment variables, providing flexibility to work across different environments.

Configuration

The database connection URL is primarily configured through environment variables. The config.py module in the project constructs the database URL based on these environment variables.

If the necessary environment variables are not set, the configuration falls back to the sqlalchemy.url specified in the alembic.ini file.

Database Schema

Running Migrations

Before running the server, Alembic is invoked to migrate the database to the most up-to-date revision (the "head"). The start.py script has been augmented to include this step.

In the env.py file, the following code is used to set the database URL:

Try to import config module and get the database URL

Attempt to get the configuration from the server config, but if that fails use the default from the alembic config

try:
     from app.core.config import settings
     config.set_main_option('sqlalchemy.url',settings.SQLALCHEMY_DATABASE_URI)
 except Exception:
     pass

Now proceed with the rest of the env.py file...

if context.is_offline_mode(): run_migrations_offline() else: run_migrations_online()