Memory leak #1892
Description
Describe the bug
The library seems to leak memory over time
To Reproduce
Run this vitest:
import { describe, expect, test } from "vitest";
import { Window as HappyWindow } from "happy-dom";
import { JSDOM } from "jsdom";
const HTML = `<!doctype html><html><body><article><h1>Hi</h1><p>${"x ".repeat(
5000
)}</p></article></body></html>`;
const pretty = (b: number) => (b / (1024 * 1024)).toFixed(2) + " MB";
const mem = () => process.memoryUsage();
async function forceGC() {
try {
// @ts-ignore
if (typeof Bun !== "undefined" && typeof Bun.gc === "function") Bun.gc(true);
// @ts-ignore
if (typeof globalThis.gc === "function") globalThis.gc();
} catch {}
await new Promise((r) => setTimeout(r, 10));
}
async function runHappyDom(iterations: number) {
for (let i = 0; i < iterations; i++) {
const win = new HappyWindow();
const doc = win.document;
doc.write(HTML);
doc.close();
}
}
async function runJSDOM(iterations: number) {
for (let i = 0; i < iterations; i++) {
const dom = new JSDOM(HTML);
const { document: doc } = dom.window;
dom.window.close();
}
}
async function runOneCycle(iterations: number, label: string, run: (iterations: number) => Promise<void>) {
await forceGC();
await run(iterations);
await forceGC();
const memorySnapshot = mem();
console.log(`${label}: heap=${pretty(memorySnapshot.heapUsed)}, rss=${pretty(memorySnapshot.rss)}`);
return { heapUsed: memorySnapshot.heapUsed, rss: memorySnapshot.rss };
}
async function runAllCycles(cycles: number, iterationsPerCycle: number, label: string, run: (iterations: number) => Promise<void>) {
const results: Array<{ heapUsed: number; rss: number }> = [];
for (let i = 1; i <= cycles; i++) {
results.push(await runOneCycle(iterationsPerCycle, `${label} cycle ${i}`, run));
}
return results;
}
type ThresholdsMB = {
heap: number;
rss: number;
}
describe("DOM libraries memory behavior", () => {
const cases = [
{ label: 'jsdom', runner: runJSDOM },
{ label: 'happydom', runner: runHappyDom },
]
const thresholdsMB: ThresholdsMB = {
heap: 10,
rss: 15
}
test.each(cases)(
'$label memory change over time is below threshold',
async ({ label, runner }) => {
const results = await runAllCycles(40, 100, label, runner)
// Calculate deltas between adjacent cycles
const heapDeltas: number[] = [];
const rssDeltas: number[] = [];
for (let i = 1; i < results.length; i++) {
const prev = results[i - 1];
const curr = results[i];
if (prev && curr) {
heapDeltas.push(curr.heapUsed - prev.heapUsed);
rssDeltas.push(curr.rss - prev.rss);
} else {
console.warn(`Missing result for cycle ${i}`);
}
}
// Average delta per cycle
const heapSum = heapDeltas.reduce((a, b) => a + b, 0);
const rssSum = rssDeltas.reduce((a, b) => a + b, 0);
const heapAvg = heapDeltas.length ? heapSum / heapDeltas.length : 0;
const rssAvg = rssDeltas.length ? rssSum / rssDeltas.length : 0;
console.log(`Average heap delta per cycle: ${pretty(heapAvg)}`);
console.log(`Average RSS delta per cycle: ${pretty(rssAvg)}`);
// Thresholds for average stabilization (tune as needed)
const heapDeltaThreshold = thresholdsMB.heap * 1024 * 1024;
const rssDeltaThreshold = thresholdsMB.rss * 1024 * 1024;
// The average delta should be close to zero (stabilizing)
expect.soft(Math.abs(heapAvg), `heap average delta per cycle not stabilized: ${pretty(heapAvg)}`).toBeLessThan(heapDeltaThreshold);
expect.soft(Math.abs(rssAvg), `rss average delta per cycle not stabilized: ${pretty(rssAvg)}`).toBeLessThan(rssDeltaThreshold);
},
300_000
);
});Expected behavior
Happy dom shouldn't eat RAM
Screenshot
Device:
- OS: Linux (WSL 2)
- Runtime: Both node and bun
- Version : 18.0.1
Additional context
if I switch order of the tests it seems like JSDOM is also affected. happydom then jsdom. Then both tests fail. I guess the happydom memory leak creates som kind of difficult or corrupt state, making also JSDOM eat RAM.
Git repo with reproduction
https://github.com/gunhaxxor/happy-dom-memory-leak