Code Monkey home page Code Monkey logo

automated-chrome-profiling's Introduction

Let's say you want to evaluate the performance of some clientside JavaScript and want to automate it. Let's kick off our measurement in Node.js and collect the performance metrics from Chrome. Oh yeah.

We can use the Chrome debugging protocol and go directly to how Chrome's JS sampling profiler interacts with V8.

So much power here, so we'll use chrome-remote-interface as a nice client in front of the protocol:

npm install chrome-remote-interface

Run Chrome with an open debugging port:

# linux
google-chrome --remote-debugging-port=9222

# mac
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --remote-debugging-port=9222

Let's profile!

Here's what we're about to…

  • Open http://localhost:8080/perf-test.html
  • Start profiling
  • run startTest();
  • Stop profiling and retrieve the profiling result
  • We can then load the data into Chrome DevTools to view

Code

var fs = require('fs');
var Chrome = require('chrome-remote-interface');

Chrome(function (chrome) {
    with (chrome) {
        Page.enable();
        Page.loadEventFired(function () {
            // on load we'll start profiling, kick off the test, and finish
            // alternatively, Profiler.start(), Profiler.stop() are accessible via chrome-remote-interface
            Runtime.evaluate({ "expression": "console.profile(); startTest(); console.profileEnd();" });
        });

        Profiler.enable();
        
        // 100 microsecond JS profiler sampling resolution, (1000 is default)
        Profiler.setSamplingInterval({ 'interval': 100 }, function () {
            Page.navigate({'url': 'http://localhost:8000/perf-test.html'});
        });

        Profiler.consoleProfileFinished(function (params) {
            // CPUProfile object (params.profile) described here:
            //    https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/devtools/protocol.json&q=protocol.json%20%22CPUProfile%22,&sq=package:chromium

            // Either:
            // 1. process the data however you wish… or,
            // 2. Use the JSON file, open Chrome DevTools, Profiles tab,
            //    select CPU Profile radio button, click `load` and view the
            //    profile data in the full devtools UI.
            var file = 'profile-' + Date.now() + '.cpuprofile';
            var data = JSON.stringify(params.profile, null, 2);
            fs.writeFileSync(file, data);
            console.log('Done! See ' + file);
            close();
        });
    }
}).on('error', function () {
    console.error('Cannot connect to Chrome');
});

For asynchronous tests, the code would be:

Runtime.evaluate({ "expression": "console.profile(); startTest(function() { console.profileEnd(); });" });

// ...

function startTest(cb) {
    foo.on('end', cb);
    foo.startAsync();
}

This is just the tip of the iceberg when it comes to using the protocol to manipulate and measure the browser. Plenty of other projects around this space as well: Chromium Telemetry, ChromeDriver frontend for WebDriver, trace-viewer, the aforementioned chrome-remote-interface Node API, and a number of other debugging protocol client applications collected here. browser-perf and its viewer perfjankie are definitely worth a look as well.

Why profile JS like this?

Well, it started because testing the performance of asynchronous code is difficult. Obviously measuring endTime - startTime doesn't work. However, using a profiler gives you the insight of how many microseconds the CPU spent within each script, function and its children, making analysis much more sane.

Contributors

automated-chrome-profiling's People

Contributors

cyrus-and avatar paulirish avatar vladikoff avatar

Watchers

 avatar

Recommend Projects

  • React photo React

    A declarative, efficient, and flexible JavaScript library for building user interfaces.

  • Vue.js photo Vue.js

    🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.

  • Typescript photo Typescript

    TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

  • TensorFlow photo TensorFlow

    An Open Source Machine Learning Framework for Everyone

  • Django photo Django

    The Web framework for perfectionists with deadlines.

  • D3 photo D3

    Bring data to life with SVG, Canvas and HTML. 📊📈🎉

Recommend Topics

  • javascript

    JavaScript (JS) is a lightweight interpreted programming language with first-class functions.

  • web

    Some thing interesting about web. New door for the world.

  • server

    A server is a program made to process requests and deliver data to clients.

  • Machine learning

    Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.

  • Game

    Some thing interesting about game, make everyone happy.

Recommend Org

  • Facebook photo Facebook

    We are working to build community through open source technology. NB: members must have two-factor auth.

  • Microsoft photo Microsoft

    Open source projects and samples from Microsoft.

  • Google photo Google

    Google ❤️ Open Source for everyone.

  • D3 photo D3

    Data-Driven Documents codes.