We launched the new walkerart.org late on December 1, and it’s been a great ride. The month leading up to (and especially the preceding week starting Thanksgiving Day, when I was physically moving servers and virtualizing old machines) was incredibly intense and really brought the best out of our awesome team. I would be remiss if I didn’t start this post by thanking Eric & Chris for their long hours and commitment to the site, Robin for guiding when needed and deflecting everything else so we could do what we do, and Andrew and Emmet for whispering into Eric’s ear and steering the front-end towards the visual delight we ended up with. And obviously Paul and everyone writing for the site, because without content it’s all just bling and glitz.
Here’s the dirty truth of the homepage when we kicked it out the door December 1:
12/1: 2.6 MB over 164 requests. Load times are pretty subjective depending on a lot of things, but we had good evidence of the page taking at least 4+ seconds from click to being usable — and MUCH longer in some cases. Everyone was clearly willing to cut us some slack with a shiny new site, but once the honeymoon is over we need to be usable every day — and that means fast. This issue pretty quickly moved to the top of our priority list the Monday after launch, December 5.
The first thing to tackle was the size: 2.6 MB is just way too big. Eric noticed our default image scaling routine was somehow not compressing jpgs (I know, duh), so that was an easy first step and made a huge difference in download size.
12/5: 1.9 MB.
On the 6th we discovered (again, duh) lossless jpeg and png compression and immediately applied it to all the static assets on the site, but not yet to the dynamically-generated versions. Down to 1.8 MB. We also set up a fake Content Delivery Network (CDN) to help “parallelize” our image downloads. Modern browsers allow six simultaneous connections to a single domain, so by hosting all our images at www.walkerart.org we were essentially trying to send all our content through one tiny straw. Chris was able to modify our image generator code to spread requests across three new domains: cdn0.walkerart.org, cdn1, etc. This bypasses the geography and fat pipe of a real CDN, but does give the end user a few more straws to suck content through.
Requests per Domain
By the 8th we were ready to push out global image optimization and blow away the cache of too-big images we’d generated. I’m kind of astounded I’d never done this on previous sites, considering what an easy change it was and what a difference it made. We’re using jpegoptim and optipng, and it’s fantastic: probably 30% lossless saving on already compressed jpegs and pngs. No-brainer.
12/8: 1.4 MB, almost half of what we launched with.
Meanwhile, I spent the weekend pulling work from the client’s browser back to the server where we could cache it site-wide. This doesn’t really impact bytes transferred, but it does remove a remote API call, which could take anywhere from a fraction of a second (unnoticeable) to several seconds in a worst-case scenario (un-usable). This primarily meant writing code to regularly call and cache all of our various Twitter feeds and the main weather widget. These are now served in the cached HTML and it’s negligible in the load time, instead of 200+ ms on average. It all adds up!
CSS Sprite for Header and Footer nav images (it has a transparent background, so it’s supposed to look like that):
12/12: 1.37 MB, and 125 requests
Happily (as I was writing this) Eric just pushed out the last (for now) CSS sprite, giving us these final numbers:
12/13: 1.37 MB, and 110 requests! (down 53% and 67% respectively)
This isn’t over, but it’s gotten to the point of markedly diminishing returns. We’re fast enough to be pretty competitive and no longer embarrassing on an iPad, but there are a few more things to pick off around the edges. We’re heavier and slower than most of our museum peers, but lighter and faster than a lot of similar news sites. Which one are we? Depends which stats I want to compare. :)