How to handle memory leaks in Node.js

Short answer

Memory leaks occur when objects are no longer needed but remain referenced. Detect them by monitoring heap usage and analyzing heap snapshots.

Steps

1. Monitor memory usage with --inspect and Chrome DevTools.
2. Take heap snapshots before and after suspected leak periods.
3. Compare snapshots to identify retained objects.
4. Look for common causes: global variables, unclosed event listeners, and closures holding large scopes.
5. Fix by removing listeners, nullifying references, and using WeakMap where appropriate.

Tips

• Use monitoring tools like clinic.js or New Relic to track heap trends over time.
• Set --max-old-space-size cautiously; increasing it only delays the symptom without fixing the leak.

Common issues

• Adding event listeners in request handlers without removing them leaks memory per request.
• Recursive setInterval timers accumulate if never cleared.