GitHub Classroom Autograder

An automated grading system for GitHub Classroom assignments that clones student repositories, runs test scripts, collects performance metrics, and generates a leaderboard with results.

Table of Contents

• Overview
• Features
• Installation
• Configuration
  • Step 1: Copy the Example Configuration
  • Step 2: Configure the Grader Section
  • Step 3: Configure Assignments
  • Step 4: Configure SLURM Backend
• GitHub Personal Access Token
• Running the Grader
• Setting Up as a Recurrent Task
• Test Script Format
• Output Format

Overview

This grading system automates the process of:

1. Fetching student submissions from GitHub Classroom
2. Cloning student repositories
3. Running test scripts with configurable SLURM resources
4. Collecting results including pass/fail status and performance metrics
5. Generating a JSON leaderboard with all results

Features

• Automated GitHub Classroom Integration: Fetches assignments and submissions via GitHub API
• SLURM Support: Execute test scripts with configurable SLURM resources (CPU, memory, GPUs, etc.)
• Performance Metrics: Collects runtime statistics from test scripts
• Flexible Assignment Identification: Use invite links, slugs, or assignment IDs
• Blocking/Non-blocking Execution: Control whether to wait for assignment completion
• Repository Cleanup: Option to preserve or delete cloned repositories
• Leaderboard Generation: JSON output with all results and metrics

Installation

1. Clone this repository
2. Install dependencies using uv or pip:

   uv sync
   # or
   pip install -r requirements.txt
   

Configuration

Step 1: Copy the Example Configuration

Create your configuration file by copying the example:

cp grader-config-example.yaml grader-config.yaml

Step 2: Configure the Grader Section

Edit the grader section in grader-config.yaml:

grader:
  working_dir: "/tmp/grader"
  grades_file: "leaderboard.json"
  github_pat: "github_pat_xxxxx"  # Optional, can use ENV variable instead

Field Explanations:

• working_dir: Directory where student repositories will be cloned. This directory must exist before running the grader.
• grades_file: Path to the output JSON file containing all grading results and the leaderboard.
• github_pat: (Optional) Your GitHub Personal Access Token. Can be omitted if provided via environment variable (see GitHub Personal Access Token section).

Step 3: Configure Assignments

Add assignments to the assignments list:

assignments:
  - name: "vector-sum"
    invite_link: "https://classroom.github.com/a/example1"
    skip: false
    preserve_repo_files: false
    blocking: true
    test_script_path: "./test_scripts/test_vectorsum.sh"
    
    slurm_backend:
      config:
        slurm_partition: "short"
        timeout_min: 60
        mem_gb: 4
        nodes: 1
        tasks_per_node: 1
        cpus_per_task: 2
        gpus_per_node: 0

Field Explanations:

• name (required): A unique identifier for the assignment. Used as the key in the output JSON.

• Assignment Identification (at least one required):

  • invite_link: The GitHub Classroom assignment invite URL (e.g., https://classroom.github.com/a/xxxxx)
  • slug: The assignment slug from GitHub Classroom (alternative to invite_link)
  • id: The numeric assignment ID (alternative to invite_link or slug)

  Note: You only need to provide one of these three identifiers.

• skip (default: false): If true, this assignment will be skipped during grading.

• preserve_repo_files (default: false): If true, cloned repositories will not be deleted after grading. Useful for debugging.

• blocking (default: false): If true, the grader will wait for this assignment's grading to complete before proceeding to the next assignment. Useful for sequential processing or when assignments have dependencies.

• test_script_path (required): Absolute or relative path to the test script that will be executed in each student's repository.

Step 4: Configure SLURM Backend

The slurm_backend.config section accepts parameters that are passed directly to submitit, which manages SLURM job submissions.

slurm_backend:
  config:
    slurm_partition: "short"      # SLURM partition name
    timeout_min: 120              # Maximum runtime in minutes
    mem_gb: 8                     # Memory allocation in GB
    nodes: 1                      # Number of nodes
    tasks_per_node: 1             # Tasks per node
    cpus_per_task: 8              # CPUs per task
    gpus_per_node: 0              # GPUs per node

Common Parameters (from submitit):

• slurm_partition: SLURM partition/queue name
• timeout_min: Job timeout in minutes
• mem_gb: Memory allocation per node in gigabytes
• nodes: Number of compute nodes
• tasks_per_node: Number of MPI tasks per node
• cpus_per_task: Number of CPU cores per task
• gpus_per_node: Number of GPUs per node
• slurm_account: SLURM account to charge (if required)
• slurm_qos: Quality of Service specification

For a complete list of available parameters, refer to the submitit documentation.

GitHub Personal Access Token

The grader requires a GitHub Personal Access Token (PAT) with appropriate permissions to access GitHub Classroom data and clone student repositories.

Creating a PAT

1. Go to GitHub Settings → Developer settings → Personal access tokens → Tokens (classic)
2. Generate a new token with the following scopes:
   • repo (Full control of private repositories)
   • read:org (Read organization data)
   • admin:org (if managing classroom assignments)

Providing the PAT

You have two options:

Option 1: Environment Variable (Recommended)

export GH_PAT="github_pat_xxxxx"
uv run main.py

Or inline:

GH_PAT="github_pat_xxxxx" uv run main.py

Option 2: Configuration File

Add it directly to grader-config.yaml:

grader:
  github_pat: "github_pat_xxxxx"

As shown in main.py, the environment variable takes precedence over the config file value:

token = os.getenv("GH_PAT") or config.config.grader.github_pat

Running the Grader

Once configured, run the grader:

uv run main.py
# or
python main.py

The grader will:

1. Read the configuration file
2. For each assignment (unless skipped):
   • Fetch student submissions from GitHub Classroom
   • Clone each student's repository
   • Copy the test script to the repository
   • Execute the test script
   • Parse the output for test results and performance metrics
   • Clean up (unless preserve_repo_files is true)
3. Save all results to the grades_file

Setting Up as a Recurrent Task

To run the grader automatically at regular intervals without administrator privileges, you can use cron (Linux/macOS) or systemd user timers.

Option 1: Using Cron

1. Open your crontab for editing:

   crontab -e
   

2. Add a cron job to run the grader. Examples:

   Run every day at 2 AM:

   0 2 * * * cd /path/to/grader && /usr/bin/uv run main.py >> /path/to/grader/cron.log 2>&1
   

   Run every 6 hours:

   0 */6 * * * cd /path/to/grader && /usr/bin/uv run main.py >> /path/to/grader/cron.log 2>&1
   

   Run every Monday at 9 AM:

   0 9 * * 1 cd /path/to/grader && /usr/bin/uv run main.py >> /path/to/grader/cron.log 2>&1
   

3. Make sure to:

   • Use absolute paths for both the grader directory and the uv executable
   • Export the GH_PAT environment variable in the cron job if not using the config file:

     0 2 * * * cd /path/to/grader && GH_PAT="github_pat_xxxxx" /usr/bin/uv run main.py >> /path/to/grader/cron.log 2>&1
     

Option 2: Using Systemd User Timer

Systemd user timers don't require root privileges and offer more control.

1. Create a service file at ~/.config/systemd/user/grader.service:

   [Unit]
   Description=GitHub Classroom Autograder
   
   [Service]
   Type=oneshot
   WorkingDirectory=/path/to/grader
   Environment="GH_PAT=github_pat_xxxxx"
   ExecStart=/usr/bin/uv run main.py
   
   [Install]
   WantedBy=default.target
   

2. Create a timer file at ~/.config/systemd/user/grader.timer:

   [Unit]
   Description=Run GitHub Classroom Autograder daily
   
   [Timer]
   OnCalendar=daily
   Persistent=true
   
   [Install]
   WantedBy=timers.target
   

3. Enable and start the timer:

   systemctl --user daemon-reload
   systemctl --user enable grader.timer
   systemctl --user start grader.timer
   

4. Check timer status:

   systemctl --user list-timers
   systemctl --user status grader.timer
   

Timer Schedule Examples:

• OnCalendar=daily - Run once per day at midnight
• OnCalendar=*-*-* 02:00:00 - Run daily at 2 AM
• OnCalendar=Mon *-*-* 09:00:00 - Run every Monday at 9 AM
• OnCalendar=*-*-* 00/6:00:00 - Run every 6 hours

Test Script Format

Your test scripts must output results in the following JSON format on the last line of stdout:

{"passed": 12, "total": 12, "times": [442.44, 664.42, 886.58]}

Required Fields:

• passed: Number of tests passed (integer)
• total: Total number of tests (integer)
• times: Array of runtime measurements in milliseconds (array of floats)

Example Test Script Output:

#!/bin/bash
# ... test execution ...
echo "Test 1: PASSED"
echo "Test 2: PASSED"
echo "Test 3: FAILED"

# Last line must be JSON
echo '{"passed": 2, "total": 3, "times": [123.45, 234.56, 345.67]}'

Output Format

The grader produces a JSON file (specified in grades_file) with the following structure:

{
  "assignment-name": [
    {
      "name": "Student Name",
      "commit_hash": "abc1234",
      "status": "graded",
      "error": "",
      "stdout": "Test output...",
      "avg_runtime": 123.456,
      "data": {
        "passed": 10,
        "total": 10,
        "times": [100.0, 120.5, 150.3]
      }
    }
  ]
}

Field Descriptions:

• name: Student name(s) associated with the submission
• commit_hash: Git commit hash (first 7 characters) of the graded submission
• status: Grading status ("graded" or "error")
• error: Error message if status is "error", empty otherwise
• stdout: Complete output from the test script
• avg_runtime: Average of all runtime values from the times array (in milliseconds)
• data: The parsed JSON output from the test script (see Test Script Format)

Troubleshooting

Issue: "GitHub Personal Access Token (PAT) not provided"

• Make sure you've set the GH_PAT environment variable or added github_pat to the config file
• Verify the token has the correct permissions

Issue: "working_dir does not exist"

• Create the directory specified in working_dir before running: mkdir -p /tmp/grader

Issue: Test script not found

• Verify the test_script_path points to an existing file
• Use absolute paths or ensure relative paths are correct from the grader directory

Issue: Test results not showing in output

• Ensure your test script outputs valid JSON on its last line
• Check that the JSON format matches exactly: {"passed": X, "total": Y, "times": [...]}
• Review test script stdout in the leaderboard JSON for debugging

Issue: Cron job not running

• Check cron logs: grep CRON /var/log/syslog (Linux) or log show --predicate 'process == "cron"' --last 1h (macOS)
• Verify absolute paths in the crontab entry
• Ensure the cron output log file is writable

License

This project is licensed under the GNU General Public License v3.0 - see the LICENSE file for details.

Copyright (C) 2026

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.