HIGH: API Gateway has no global Express error handler or graceful shutdown

[Senthil455]

Summary

The API Gateway has no global Express error handler. Async middleware rejections become unhandled promise rejections, crashing the process in Node.js 20+.

Affected File

services/api-gateway-node/index.js

Root Cause

Express 5 requires a global error handler middleware to catch errors from async route handlers and middleware. Without it:

// Missing:
app.use((err, req, res, next) => {
    console.error('Unhandled error:', err);
    res.status(500).json({ error: 'Internal server error' });
});

Any synchronous throw or async rejection in route handlers or middleware will:

1. Crash the process (Node.js 20+ terminates on unhandled rejections)
2. Return a generic HTML error page instead of JSON
3. Leak stack traces to the client

Additionally, there is no graceful shutdown:

// Missing:
process.on('SIGTERM', () => {
    server.close(() => process.exit(0));
});

Impact

• Any unhandled error crashes the entire API Gateway
• All downstream services become unreachable
• Unhandled promise rejections terminate the Node.js process
• In production, this causes cascading failures across the entire platform

Fix Required

1. Add a global Express error handler:

app.use((err, req, res, next) => {
    logger.error('unhandled_error', { error: err.message, stack: err.stack });
    res.status(err.status || 500).json({ error: 'Internal server error' });
});

2. Add graceful shutdown handlers for SIGTERM/SIGINT
3. Use express-async-errors or ensure all async handlers catch errors

[Senthil455]

Fixed in PR #117 - Added global 4-argument Express error handler + SIGTERM/SIGINT graceful shutdown