chrome-har-capturer

Capture HAR files from a remote Chrome instance.

Under the hood this module uses chrome-remote-interface to instrument Chrome.

Usage

Start Chrome with options:

• --remote-debugging-port=<port> to enable the Remote Debugging Protocol on the port <port>;

• --enable-benchmarking --enable-net-benchmarking to enable the Javascript interface that allows chrome-har-capturer to flush the DNS cache and the socket pool before loading each URL.

For example:

google-chrome --remote-debugging-port=9222 \
              --enable-benchmarking \
              --enable-net-benchmarking

Use the bundled utility

Usage: chrome-har-capturer [options] URL...

Options:

  -h, --help           output usage information
  -t, --host <host>    Remote Debugging Protocol host
  -p, --port <port>    Remote Debugging Protocol port
  -o, --output <file>  dump to file instead of stdout
  -c, --content        also capture the requests body
  -a, --agent <agent>  user agent override
  -d, --delay <ms>     time to wait after the load event
  -g, --give-up <s>    time to wait before giving up
  -f, --force          continue even without benchmarking extension
  -v, --verbose        enable verbose output on stderr

This module comes with a utility that can be used to generate a cumulative HAR file from a list of URLs.

Install globally with:

sudo npm install -g chrome-har-capturer

Load a list of URL with:

chrome-har-capturer -o out.har \
    https://github.com \
    http://www.reddit.com \
    http://iwillfail \
    http://www.reddit.com/help/faq

Write a custom application

Install locally with:

npm install chrome-har-capturer

The following snippet loads an array of URLs serially and generate a cumulative HAR file, just like the Record button in the Network Panel of Chrome Developer Tools.

var fs = require('fs');
var chc = require('chrome-har-capturer');
var c = chc.load(['https://github.com',
                  'http://www.reddit.com',
                  'http://iwillfail',
                  'http://www.reddit.com/help/faq']);
c.on('connect', function () {
    console.log('Connected to Chrome');
});
c.on('end', function (har) {
    fs.writeFileSync('out.har', JSON.stringify(har));
});
c.on('error', function (err) {
    console.error('Cannot connect to Chrome: ' + err);
});

API

load(urls, [options])

Connects to a remote instance of Google Chrome using the Remote Debugging Protocol and loads a list of URLs serially. Returns an instance of the Client class.

urls is either an array or a single URL (note that URLs must contain the schema, otherwise they will be rejected by Chrome).

options is an object with the following optional properties:

• host: Remote Debugging Protocol host. Defaults to localhost;
• port: Remote Debugging Protocol port. Defaults to 9222;
• chooseTab: Callback used to determine which remote tab attach to. Takes the JSON array returned by http://host:port/json containing the tab list and must return the numeric index of a tab. Defaults to a function that returns the active one (function (tabs) { return 0; });
• fetchContent: If true also capture the requests body. Defaults to false;
• userAgent: String used to override the user agent. Defaults to the original value;
• onLoadDelay: Milliseconds to wait after the load event is fired before stop capturing events. Defaults to 0;
• giveUpTime; Seconds to wait before giving up with the current URL;
• force: If true continue even without the benchmarking extension support; useful to inspect Chrome for Android. Note that in this way the DNS cache and socket pool are not flushed. Defaults to false.

setVerbose([verbose])

Enable or disable verbose prints for debugging purposes.

verbose: Verbosity flag. Defaults to true.

Class: Client

Event: 'connect'

function () {}

Emitted when a connection to Chrome has been established.

Event: 'pageStart'

function (url) {}

Emitted when Chrome is about to load url.

Event: 'pageEnd'

function (url) {}

Emitted when Chrome has finished loading url.

Event: 'pageError'

function (url) {}

Emitted when Chrome has failed loading url. Failed URLs will not appear in the cumulative HAR object.

Event: 'end'

function (har) {}

Emitted when every given URL has been loaded. har is the cumulative HAR object.

Event: 'error'

function (err) {}

Emitted when http://host:port/json can't be reached or if there are unexpected behaviors with Chrome. err in an instance of Error.

Resources

• HAR 1.2 Spec
• HAR Viewer
• Chrome Developer Tools: Remote Debugging Protocol v1.1