memlab

memlab

memlab is an E2E testing and analysis framework for finding JavaScript memory leaks in Chromium. The CLI Toolbox and library provide extensible interfaces for analyzing heap snapshots taken from Chrome/Chromium, Node.js, Hermes, and Electron.js.

CLI Usage

Install the CLI

npm install -g @memlab

Find Memory Leaks

To find memory leaks in Google Maps, you can create a scenario file defining how to interact with the Google Maps, let's name it test-google-maps.js:

// initial page load url: Google Maps
function url() {
  return 'https://www.google.com/maps/@37.386427,-122.0428214,11z';
}

// action where we want to detect memory leaks: click the Hotels button
async function action(page) {
  await page.click('button[aria-label="Hotels"]');
}

// action where we want to go back to the step before: click clear search
async function back(page) {
  await page.click('[aria-label="Clear search"]');
}

module.exports = {action, back, url};

Now run memlab with the scenario file, memlab will interact with the web page and detect memory leaks with built-in leak detectors:

memlab run --scenario test-google-maps.js

If you want to use a self-defined leak detector, add a filterLeak callback in the scenario file. filterLeak will be called for every unreleased heap object (node) allocated by the target interaction.

function filterLeak(node, heap) {
  // ... your leak detector logic
  // return true to mark the node as a memory leak
};

heap is the graph representation of the final JavaScript heap snapshot.

Heap Analysis and Investigation

View which object keeps growing in size during interaction in the previous run:

memlab analyze unbound-object

Analyze pre-fetched v8/hermes .heapsnapshot files:

memlab analyze unbound-object --snapshot-dir <DIR_OF_SNAPSHOT_FILES>

Use memlab analyze to view all built-in memory analyses. For extension, view the doc site.

View retainer trace of a particular object:

memlab trace --node-id <HEAP_OBJECT_ID>

Use memlab help to view all CLI commands.

APIs

Use the memlab npm package to start a E2E run in browser and detect memory leaks.

const memlab = require('memlab');

const scenario = {
    // initial page load url
    url: () => 'https://www.google.com/maps/@37.386427,-122.0428214,11z',

    // action where we want to detect memory leaks
    action: async (page) => await page.click('button[aria-label="Hotels"]'),

    // action where we want to go back to the step before
    back: async (page) => await page.click('[aria-label="Clear search"]'),
}
memlab.run({scenario});