Google Ajax Crawler

Rack Middleware adhering to the Google Ajax Crawling Scheme, using a headless browser to render JS heavy pages and serve a dom snapshot of the rendered state to a requesting search engine.

Details of the scheme can be found at: https://developers.google.com/webmasters/ajax-crawling/docs/getting-started

Using

install

gem install google_ajax_crawler

In your config.ru

require 'google_ajax_crawler'

use GoogleAjaxCrawler::Crawler do |config|
  config.page_loaded_test = lambda {|driver| driver.page.evaluate_script('document.getElementById("loading") == null') }
end

app = lambda {|env| [200, {'Content-Type' => 'text/plain'}, "b" ] }
run app

Examples

In the examples folder, each driver has a rackup file (at the moment only one driver, capybara-webkit, exists), which can be launched:

rackup examples/capybara_webkit.ru

Examples for how to use the crawler with Backbone.JS, Angular.JS and plain ol javascript are accesible via:

• http://localhost:9292/backbone
• http://localhost:9292/angular
• http://localhost:9292/

Open a browser to http://localhost:9292/[framework]#!test and view source.... This is how a search engine will see your page. NOTE: don't look at the markup through a web inspector as it will most likely display dom elements rendered on the fly by js.

Change the url to http://localhost:9292/[framework]?_escaped_fragment_=test , and then again view source to see how the DOM state has been captured

Configuration Options

page_loaded_test

Tell the crawler when your page has finished loading / rendering. As determining when a page has completed rendering can depend on a number of qualitative factors (i.e. all ajax requests have responses, certain content has been displayed, or even when there are no loaders / spinners visible on the page), the page loaded test allows you to specify when the crawler should decide that your page has finished loading / rendering and to return a snapshot of the rendered dom at that time.

The current crawler driver is passed to the lambda to allow querying of the current page's dom state.

A good pattern is to test your page state in a js function returning a boolean, accessible from the window context.. i.e.

use GoogleAjaxCrawler::Crawler do |config|
  config.page_loaded_test = lambda {|driver| driver.page.evaluate_script('myApp.isPageLoaded()') }
end

timeout

The max time (in seconds) the crawler should wait before returning a response. After the timeout has been reached, a snapshot of the DOM in its current state is returned. Defaults to 30 seconds.

driver

The configured google ajax crawler driver used to query the current page state. Defaults to capybara_webkit.

poll_interval

How often (in seconds) to test the page state with the configured page_loaded_test. Defaults to 0.5 seconds.

response_headers

What response headers shoudl be returned with the dom snapshot. Default headers specify the content-type text/html.

requested_route_key

The parameter name used by a search bot to idenitfy which client side route to snapshot. Defaults to escaped_fragment.

License

All free - Use, modify, fork to your hearts content... See LICENSE.txt for further details.