Memory Leak Hunting in Node.js

Memory Leak Hunting in Node.js¶

Is Node.js eating memory? A systematic guide to finding and fixing memory leaks.

Detection¶

setInterval(() => console.log(Heap: ${Math.round(process.memoryUsage().heapUsed/1024/1024)} MB), 10000);

Chrome DevTools¶

node –inspect app.js

chrome://inspect -> Memory -> Heap snapshot¶

Causes¶

Event Listeners¶

// emitter.on(‘data’, handler) in a loop // emitter.once() or removeListener

Closures¶

A closure holds a reference to a large object that the GC would otherwise collect.

Global Cache¶

// const cache = {}; cache[key] = data; // grows without limit // LRUCache with max size

Unclosed Streams¶

Always close DB connections, file streams and HTTP connections.

LRU Cache¶

import { LRUCache } from ‘lru-cache’; const cache = new LRUCache({ max: 500 });

Procedure¶

Heap snapshot -> compare 3 snapshots -> find growing objects -> fix.