I’m willing to bet you’re going to find Google Ajax Libraries is better in every metric, but for the sake of discussion let’s assume there’s enough of an issue that you’d like to pursue this. Even if the outages are rare, it’d be nice to have a fallback because it’s less likely both Google and your servers would be down at the same time.

I’ve never worked on this before, but you could use something like the image/object script loading technique from ControlJS/Stoyan and load BOTH versions of jquery simultaneously. Remember that with these techniques the script is downloaded but is NOT parsed & executed. Then, whichever script comes back first is the one you’ll use.

I realize this has been around for a couple years, and I love the concept, but I’ve been stalling to implement it for a certain site because we have time-sensitive functionality (real-time bidding on auctions), and despite the fact Google’s servers are generally extremely fast, sometimes they’re slow, and that could have major consequences for us.

I realize there are workarounds to load jQuery from our own server when Google is down or blocked, but is there anything we can do for times when Google is just plain slow? The reasoning is we can justify the occasional problem on our own servers, because if jQuery is not loading, we have bigger problems, and our customers are probably aware, and we’ll make sure we accommodate those users in our auctions, but if Google CDN starts running slowly for customers in a certain part of the country, we won’t know in time, and they won’t be happy.

Are we being overly concerned? Are we simply a bad candidate for Google CDN, due to the nature of our site? Or is there a workaround so that we can avoid this becoming an issue?

It seems like it would be ideal if we could just specify a callback that would run when the Google Loader API noticed poor response times.

I haven’t found any good solutions for this, so I’m hoping you can help.

Thanks,
Richard

The slides are available on my front page: http://stevesouders.com/ (click on the “slides” link next to “Google I/O”).

John: The choice of which versions to serve was determined by the framework teams.

Google has done a terrific work here. Though, the big problem is that they only offer full size versions of the framework, that means useless components are loaded.

I think it mainly aims the heavy web apps, but doesn’t aim the little uses of JS you can see on blogs for example.

I was thinking that adding this link to a page forces the browser to potentially do one DNS lookup more.

It would be interesting to know how large the distribution of the above files is, e.g. when the threshold of cache vs. dns lookup is reached.

And one more thing: how good is the google CDN outside the US? For example here in Germany many US-based CDNs only have one POP. With 99% of our users coming from Germany using a CDN may actually reduce the speed, since our servers sit right in the second-largest DSL providers main datacentre.