Debug Mode

How to enable and use debug mode for troubleshooting.

Enabling Debug Mode

Add to your .env file:

DEBUG=true

Then restart the server:

pm2 restart gradescope-submitter

What Debug Mode Shows

Server Logs

With debug enabled, you'll see detailed logs for:

• Incoming requests
• LTI launch validation
• Gradescope API calls
• Session management
• Error details

Example Debug Output

[DEBUG] POST /submit
[DEBUG] Request body: { code: "print('hello')", asg_id: "6617143" }
[DEBUG] Submitting to Gradescope...
[DEBUG] Course ID: 1106756
[DEBUG] Assignment ID: 6617143
[DEBUG] Response status: 200
[DEBUG] Submission URL: https://gradescope.com/...

Viewing Logs

With PM2

# View all logs
pm2 logs

# View only this app's logs
pm2 logs gradescope-submitter

# View last 100 lines
pm2 logs --lines 100

# Follow logs in real-time
pm2 logs --follow

Without PM2

# Run directly and see output
node app.js

Browser Developer Tools

Console Tab

1. Open Developer Tools (F12)
2. Go to Console tab
3. Look for:
   • JavaScript errors (red)
   • Warnings (yellow)
   • Debug messages (gray)

Network Tab

1. Open Developer Tools (F12)
2. Go to Network tab
3. Refresh the page
4. Look for:
   • Failed requests (red)
   • Slow requests
   • Response codes

Common Network Issues

Status	Meaning	Fix
404	Resource not found	Check URL/path
500	Server error	Check server logs
CORS	Cross-origin blocked	Check server headers

Debugging Specific Issues

LTI Launch Problems

Check these in order:

1. Request received? — Look for POST /lti/launch in logs
2. Payload valid? — Check for validation errors
3. Credentials match? — Verify CLIENT_ID and DEPLOYMENT_ID

Gradescope Submission Problems

Check these in order:

1. Code received? — Look for POST /submit in logs
2. Credentials valid? — Check TOKEN and COOKIE aren't expired
3. API response? — Look for Gradescope response in logs

Pyodide Problems

In browser console, look for:

// Check if Pyodide loaded
console.log(typeof loadPyodide);

// Check for load errors
// Look for "Pyodide" in console messages

Common Debug Patterns

Add Temporary Logging

In app.js:

app.post('/submit', (req, res) => {
  console.log('[DEBUG] Submit request:', req.body);
  // ... rest of handler
});

Check Environment Variables

# Print all env vars (be careful with secrets!)
node -e "console.log(process.env)"

# Check specific variable
node -e "console.log(process.env.COURSE_ID)"

Test Gradescope Connection

# Simple test (replace with your values)
curl -X POST https://www.gradescope.com/api/... \
  -H "Cookie: your-cookie" \
  -d "authenticity_token=your-token"

Disabling Debug Mode

When done debugging, remove or set to false:

DEBUG=false

And restart:

pm2 restart gradescope-submitter

WARNING

Don't leave debug mode on in production — it may expose sensitive information in logs.