[Wikitech-l] ResourceLoader, now in trunk!

MediaWiki Developers, Over the past couple of months, Roan Kattouw and I (Trevor Parscal) have been working on a JavaScript and CSS delivery system called ResourceLoader. We're really excited about this technology, and hope others will be too. This system has been proving itself to be able to seriously improve front-end performance. Just for starters, we're talking about taking the Vector skin from 35 requests @ 30kB gzipped to 1 request @ 9.4kB gzipped (see http://www.mediawiki.org/wiki/ResourceLoader/Benchmarks) We are looking to make this the standard way to deliver Javascript, CSS, and small images in MediaWiki and on Wikimedia projects, and we're seeking your comments and help. == Background == The goals of the project were to improve front-end performance, reduce the complexity of developing JavaScript libraries and user-interfaces, and get the ball rolling on a rewrite/refactoring of all JavaScript and CSS code in MediaWiki. What's wrong with things as they are now? * Too many individual requests are being made. All JavaScript, CSS and image resources are being loaded individually, which causes poor performance on the cluster and users experience the site as being slow. * We are wasting too much bandwidth. We are sending JavaScript and CSS resources with large amounts of unneeded whitespace and comments. * We are purging our caches too much. Many user interface changes require purging page caches to take effect and many assets are unnecessarily being purged from client machines due to the use of a single style version for all assets * We are sending people code they don't even use. Lots of JavaScript is being sent to clients whose browsers will either crash when it arrives (BlackBerry comes to mind), just not use it at all (older versions of many browsers) while parsing it unnecessarily (this is slow on older browsers, especially IE 6) or isn't even being completely utilized (UsabilityInitiative's plugins.combined.min.js for instance) * Internationalization in JavaScript is a mess. Developers are using many different ways -- most of which are not ideal -- to get their translated messages to the client. * Right-to-left support in CSS is akward. Stylesheets for right-to-left must to be either hand-coded in a separate stylesheet, generated each time a change is made by running CSSJanus, or an extra style-sheet which contains a series of over-rides. * There's more! These and other issues were captured in our requirements gathering process (see http://www.mediawiki.org/wiki/ResourceLoader/Requirements ) What does ResourceLoader do to solve this? * Combines resources together. Multiple scripts, styles, messages to be delivered in a single request, either at initial page load or dynamically; in both cases resolving dependencies automatically. * Allows minification of JavaScript and CSS. * Dramatically reduces the number of requests for small images. Small images linked to from CSS code can be automatically in-lined as data URLs (when the developer marks it with a special comment), and it's done automatically as the file is served without requiring the developer to do such steps manually. * Allows deployment changes to all pages for all users within minutes, without purging any HTML. ResourceLoader provides a short-expiry start-up script which then decides to continue loading more JavaScript or not, and if so has a complete manifest of all scripts and styles on the server and their most recent versions, Also, this startup script will be able to be inlined using ESI (see http://en.wikipedia.org/wiki/Edge_Side_Includes ) when using Squid or Varnish, reducing requests and improving performance even further. * Provides a standard way to deliver translated messages to the client, bundling them together with the code that uses them. * Performs automatic left-to-right/right-to-left flipping for CSS files. In most cases the developer won't have to do anything before deploying. * Does all kinds of other cool tricks, which should soon make everyone's lives better What do you want from me? * Help by porting existing code! While ResourceLoader and traditional methods of adding scripts to MediaWiki output can co-exist, the performance gains of ResourceLoader are directly related to the amount of software utilizing it. There's some more stuff in core that needs to be tweaked to utilize the ResourceLoader system, such as user scripts and site CSS. We also need extensions to start using it, especially those we are deploying on Wikimedia sites or thinking about deploying soon. Only basic documentation exists on how to port extensions, but much more will be written very shortly and we (Roan and I) be leading by example by porting the UsabilityInitiative extensions ourselves. If you need help, we're usually on IRC. (See http://www.mediawiki.org/wiki/ResourceLoader/Getting_Started ) * Help writing new code! While wikibits.js is now also known as the "mediawiki.legacy.wikibits" module, the functionality that it and basically all other existing MediaWiki JavaScript code provide is being deprecated, in favor of new modules which take advantage of jQuery and can be written using a lot less code while eliminating the current dependence on a large number of globally accessible variables and functions (see http://www.mediawiki.org/wiki/ResourceLoader/JavaScript_Deprecations ) * Some patience and understanding... Please... While we are integrating into trunk, things might break unexpectedly. We're diligently tracking down issues and resolving them as fast as we can, but help in this regard is much needed and really appreciated. But most of all, we're sorry if something gets screwed up, and we're trying our best to make this integration smooth. * Enthusiasm! Documentation is coming online as fast as we can write it. There's a very detailed design specification document at http://www.mediawiki.org/wiki/ResourceLoader/Design_Specification and more information in general at http://www.mediawiki.org/wiki/ResourceLoader , where we will be adding more and more documentation as time goes on. If you can help with documentation, please feel free to edit boldly - just try not to modify the design specification unless you are also modifying the software :) While this project has been bootstrapped by Roan and myself in a branch, we're really excited about bringing it to trunk and hope the community can start taking advantage of the new features right away. Tracking bug for tracking things that ResourceLoader will fix: http://bugzilla.wikimedia.org/show_bug.cgi?id=24415 Bugzilla Component: https://bugzilla.wikimedia.org/buglist.cgi?query_format=advanced&bug_st… - Trevor (and Roan, who's committing the merge to SVN right now)