Puppeteer: tracing.start doesn't seem to output screenshots

Created on 18 Oct 2017 · 3Comments · Source: puppeteer/puppeteer

I am trying to get a basic tracing example with screenshots option enabled work, however, it produces trace.json, but no screenshots.

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.tracing.start({screenshots: true, path: 'trace.json'});  
  await page.goto('https://www.google.com');
  await page.tracing.stop();  
  await browser.close();
})();

What is the expected result?

Produce timeline screenshots along with trace.json

What happens instead?

Produces only trace.json. No screenshots outputted.

Using the following

Puppeteer version: 0.12.0
Platform / OS version: Mac OSX 10.13
URLs (if applicable): google.com

Source

kesava

Most helpful comment

If you do want to export the trace screenshots, this quick example based on @Everettss example in issue 1368 seem to work for me.

const puppeteer = require('puppeteer');
const fs = require('fs');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  await page.tracing.start({ screenshots: true, path: 'trace.json' });
  await page.goto('https://www.google.com', { timeout: 60000 });
  await page.tracing.stop();

  // --- extracting data from trace.json ---
  const tracing = JSON.parse(fs.readFileSync('./trace.json', 'utf8'));
  const traceScreenshots = tracing.traceEvents.filter(x => (
      x.cat === 'disabled-by-default-devtools.screenshot' &&
      x.name === 'Screenshot' &&
      typeof x.args !== 'undefined' &&
      typeof x.args.snapshot !== 'undefined'
  ));
  traceScreenshots.forEach(function(snap, index) {
    fs.writeFile('trace-screenshot-'+index+'.png', snap.args.snapshot, 'base64', function(err) {
      if (err) {
        console.log('writeFile error', err);
      }
    });
  });
  // --- end extracting data from trace.json ---

  await page.close();
})();

QmarkC on 14 Dec 2017

👍3 ❤2

All 3 comments

@kesava Screenshots are embedded in the trace: try drag-and-dropping the trace.json file into devtools performance panel.

aslushnikov on 31 Oct 2017

If you do want to export the trace screenshots, this quick example based on @Everettss example in issue 1368 seem to work for me.

const puppeteer = require('puppeteer');
const fs = require('fs');

(async () => {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();

  await page.tracing.start({ screenshots: true, path: 'trace.json' });
  await page.goto('https://www.google.com', { timeout: 60000 });
  await page.tracing.stop();

  // --- extracting data from trace.json ---
  const tracing = JSON.parse(fs.readFileSync('./trace.json', 'utf8'));
  const traceScreenshots = tracing.traceEvents.filter(x => (
      x.cat === 'disabled-by-default-devtools.screenshot' &&
      x.name === 'Screenshot' &&
      typeof x.args !== 'undefined' &&
      typeof x.args.snapshot !== 'undefined'
  ));
  traceScreenshots.forEach(function(snap, index) {
    fs.writeFile('trace-screenshot-'+index+'.png', snap.args.snapshot, 'base64', function(err) {
      if (err) {
        console.log('writeFile error', err);
      }
    });
  });
  // --- end extracting data from trace.json ---

  await page.close();
})();

QmarkC on 14 Dec 2017

👍3 ❤2

@QmarkC I think it fails when chrome crashes.
How can I implement this, so that I can know at which point chrome is crashed?