How to improve puppeteer startup performance during tests - node.js

Question

I've written a small crawler with the help of Puppeteer.
Now I'm facing the challenge that my tests are rather slowly (> 3 seconds for each test). I've been able to track it down to the launch function of Puppeteer and the usage of Istanbul/nyc.
If I run the test just with mocha, the tests are finished under 400 ms.
But if I additionally use nyc, the duration of the tests exceeds 3000 ms
All that I'm using is
'use strict';
const puppeteer = require('puppeteer');
module.exports = async function startBrowser() {
const options = {
args: [
// '--no-sandbox',
// '--disable-setuid-sandbox',
// '--disable-dev-shm-usage',
// '--disable-accelerated-2d-canvas',
// '--disable-gpu'
],
headless: false // true
};
return await puppeteer.launch(options);
};
Here is the test I'm using:
'use strict';
/* global describe: false, before: false, it: false,
beforeEach: false, afterEach: false, after: false, window: false, document: false */
const assert = require('assert').strict;
const startBrowser = require('../');
const util = require('util');
describe('Puppeteer', function() {
let pageManager;
it('start the browser', async function() {
this.timeout(10000);
console.time('startBrowser');
const browser = await startBrowser();
console.timeEnd('startBrowser');
assert(browser);
console.time('closeBrowser');
await browser.close();
console.timeEnd('closeBrowser');
});
});
I've created a repository with this code and test here.
nyc _mocha ./test/*.test.js runs in ~3500ms, mocha ./test/*.test.js takes only 130ms.
What I've tried so far:
different combination of include/exclude nyc flags
updating to latest versions of Puppeteer, nyc and mocha
removing my Puppeteer arguments
searching for Puppeteer & Istanbul related issues (with not much success)
trying headless: true
bypassing all proxies, see this puppeteer issue
What can I do to have tests with coverage be as fast as the tests alone?
Using:
Ubuntu 19.04
node.js 10.15.3

Answer 1

I've started to debug Puppeteer and these are my findings:
Puppeteer is unsurprisingly using child_process.spawn() to spawn a new browser
nyc is using spawn-wrap for such child processes
spawn-wrap is reading the whole executable (./node_modules/puppeteer/.local-chromium/linux-686378/chrome-linux/chrome) into memory with fs.readFileSync which is taking an unusually long time to finish
spawn-wraps README delivers some kind of an explanation:
The initial wrap call uses synchronous I/O. Probably you should not be using this script in any production environments anyway. Also, this will slow down child process execution by a lot, since we're adding a few layers of indirection.
For me personally the answer is that I cannot get the same performance for running tests with and without code coverage as long as I use nyc/istanbul.
I've given c8 a shot, and the performance is nearly the same and I can still have code coverage.

Answer 2

Please try this also.
'use strict'
const puppeteer = require('puppeteer')
module.exports = async function startBrowser() {
const options = {
args: [
'--no-sandbox',
'--disable-setuid-sandbox',
'--disable-dev-shm-usage',
'--disable-accelerated-2d-canvas',
'--no-first-run',
'--no-zygote',
'--single-process', // <- this one doesn't works in Windows
'--disable-gpu'
],
headless: true
}
return await puppeteer.launch(options)
}

Answer 3

./Chromium --headless --disable-gpu --remote-debugging-port=9222 --devtools=false
browser = await puppeteer.connect({
browserWSEndpoint: 'ws://127.0.0.1:9222/devtools/browser/........xxxxxx..',
});
use express to hold it
PS: But ,I can't specify the browserWSEndpoint
the url change every time Chromium --headless restart