Topic:
CDNs and other optimization techniques. This comes up a lot, it crosses numerous mailing lists and twitter. If you have thoughts on this, let's discuss and we can easily cite/refernce in the future....
Here is a statement from @scott_gonzales on twitter, and some thoughts from me to open the discussion
Scott: CDNs have much higher cache-miss rates than you'd think, and JS should be concatenated and deployed from the server
Me: It's true cache-misses are higher, but I don't want to throw the baby out with the bathwater. The advantages of concat will largely disappear with HTTP2. CDNs have a number of things (some in theory and some in practice) which seem good. At an incredibly utilitarian level, if I can offload that from my own infrastructure and maybe reduce hops for this requests too - seems good. At a more conceptual level, the idea that some resources are highly shareble and deserve a special home/cache seems good even if CDNs don't currently fully enable that - seems maybe not so much a problem with the CDN as much as one for the platform to help tackle. It does seem ridiculous to send signficant capabilities like jQuery, Ember or Angular down over and over and ask them to eat up cache space in my own domain. It really seems like there should be 1 and only 1 version of content called jQuery-x.y.z.js
@scottgonzalez - If the choice is between a slimmed down self-hosted version and a bloated CDN version, then it's a no-brainer IMO (even if browser cache rates are higher on the CDN)
@bkardell - I don't believe that cache space is the issue here. Caches shouldn't evict popular resources.
I think that the problem is the multitude of framework versions + the fact that there are several "official" CDNs result in the fact that your particular choice of version+CDN is not shared by many other sites.
That means that the % of first-time-users-that-saw-your-framework-elsewhere is not that high, and even there, this particular framework+CDN combination is not recognized as a highly-popular resource (because it isn't) and may be evicted rather fast, to make space for some popular cat photos.