Error Handling

Igo.js catches errors at three levels to keep your application running.

Express Request Errors

Errors thrown in route handlers are caught, logged, and a 500 page is returned:

app.get('/api/data', async (req, res) => {
  const data = await riskyOperation(); // If this throws, error handler catches it
  res.json(data);
});

Unhandled Promise Rejections

If a promise rejects without a catch and the error happens within a request context, it's handled like an Express error. Otherwise, it's logged and re-thrown.

Uncaught Exceptions

Fatal errors that escape all handlers are logged, an email is sent, and the process exits after 1 second. Use a process manager like PM2 to restart automatically.

Special Cases

Error type	Response	Email sent?
URIError (malformed URL)	404	No
SyntaxError (invalid JSON)	500	No
Other errors	500	Yes

Crash Emails

Configure one or more recipients for error notification emails:

// app/config.js
config.mailcrashto = 'admin@example.com';
// or, for several recipients:
config.mailcrashto = ['admin@example.com', 'ops@example.com'];

The email includes: error message, stack trace, request context (method, URL, user-agent, body, session).

Email Throttling

To prevent spam during crash loops, emails are throttled per error type:

• Max 3 emails per unique error within 1 minute
• After 3 emails, the error is blocked for 5 minutes
• A final [THROTTLED] alert is sent before blocking
• Different error types are tracked independently

Throttle state is persisted in a temp file to survive restarts.