High Performance Web Sites blog

Eric Miraglia wrote a post yesterday called Combo Handler Service Available for Yahoo-hosted JS. One of the advantages of YUI over other JavaScript frameworks is its à la carte capabilities. Developers can choose just the parts they want, rather than being saddled with the whole kit and caboodle. It’s great to download fewer bytes, but choosing a subset of modules results in downloading multiple external scripts, something that’s bad for performance and costs YSlow points. That’s where Eric’s post comes in.

The Combo Handler Service lets developers choose a customized subset of modules and have them served as a single HTTP request from Yahoo!’s worldwide CDN for faster delivery. Each module (file) is listed in the querystring. As an example, Eric shows that loading the YUI Rich Text Editor the old way would require downloading six separate scripts:

<script src=”http://yui.yahooapis.com/2.5.2/build/yahoo-dom-event/yahoo-dom-event.js”>
</script>
<script src=”http://yui.yahooapis.com/2.5.2/build/container/container_core-min.js”>
</script>
<script src=”http://yui.yahooapis.com/2.5.2/build/menu/menu-min.js”>
</script>
<script src=”http://yui.yahooapis.com/2.5.2/build/element/element-beta-min.js”">
</script>
<script src=”http://yui.yahooapis.com/2.5.2/build/button/button-min.js”>
</script>
<script src=”http://yui.yahooapis.com/2.5.2/build/editor/editor-beta-min.js”>
</script>

This is reduced to a single HTTP request by using the Combo Handler:

<script src=”http://yui.yahooapis.com/combo?2.5.2/build/yahoo-dom-event/yahoo-dom-event.js&
2.5.2/build/container/container_core-min.js&2.5.2/build/menu/menu-min.js&
2.5.2/build/element/element-beta-min.js&2.5.2/build/button/button-min.js&
2.5.2/build/editor/editor-beta-min.js”>
</script>

It’s important that developers using Combo Handler pay particular attention that they get the dependency order correct. I created the YUI Combo Handler: preserving order test page to show what happens if prerequisites are listed incorrectly. In this page instead of putting editor-beta-min.js as the last querystring parameter, I make it the first parameter. Not surprisingly, the page produces JavaScript errors. It would be great if Combo Handler ensured that the response had all the necessary prerequisites in the right order. With this enhancement the single request would be much simpler:

<script src=”http://yui.yahooapis.com/combo?2.5.2/build/editor/editor-beta-min.js”>
</script>

This is a great announcement. Web developers using YUI can now get a customized rollup hosted on Yahoo!’s CDN! This is the best of all worlds - reduced download size, fewer HTTP requests, and CDN hosting. I encourage other JavaScript frameworks to adopt YUI’s à la carte flexibility. Perhaps Google Ajax Libraries could then support features to serve up customized builds similar to what Combo Handler does. Well done.

This week I co-chaired Velocity, the web performance and operations conference from O’Reilly. It was great! Jesse and I told the story about how the conference came about. When we proposed the conference we believed there was a community of performance and operations engineers that needed a forum to share and learn, and the attendance at Velocity confirmed this. Velocity sold out with over 600 attendees!

The lineup of speakers was great. There was a lot of material packed in a 2-day conference. I stayed in the Performance track, but wanted to attend every session in the Operations track, too. Many speakers shared their slides, and there are videos and photos from some of the talks.

Continue Reading »

At Web 2.0 Expo today I announce the release of Cuzillion. The tag line is ‘cuz there are zillion pages to check. It’s indispensable for people like me who are always pushing browsers to their limit trying to figure out how to squeeze out a little more performance.

I’m constantly thinking of or being asked about how browsers handle different sets of resources loaded in various ways. Before I would open an editor and build some test pages. Firing up a packet sniffer I would load these pages in different browsers to diagnose what was going on. I was starting my research on advanced techniques for loading scripts without blocking and realized the number of test pages needed to cover all the permutations was in the hundreds. That was the birth of Cuzillion. Continue Reading »