Speedy tunes

Performance is a high priority for me with The Session. It needs to work for people all over the world using all kinds of devices.

My main strategy for ensuring good performance is to diligently apply progressive enhancement. The core content is available to any device that can render HTML.

To keep things performant, I’ve avoided as many assets (or, more accurately, liabilities) as possible. No uneccessary images. No superfluous JavaScript libraries. Not even any web fonts (gasp!). And definitely no third-party resources.

The pay-off is a speedy site. If you want to see lab data, run a page from The Session through lighthouse. To see field data, take a look at data from Chrome UX Report (Crux).

But the devil is in the details. Even though most pages on The Session are speedy, the outliers have bothered me for a while.

Take a typical tune page on the site. The data is delivered from the server as HTML, which loads nice and quick. That data includes the notes for the tune settings, written in ABC notation, a nice lightweight text format.

Then the enhancement happens. Using Paul Rosen’s brilliant abcjs JavaScript library, those ABCs are converted into SVG sheetmusic.

So on tune pages there’s an additional download for that JavaScript library. That’s not so bad though—I’m using a service worker to cache that file so there’ll only ever be one initial network request.

If a tune has just a few different versions, the page remains nice and zippy. But if a tune has lots of settings, the computation starts to add up. Converting all those settings from ABC to SVG starts to take a cumulative toll on the main thread.

I pondered ways to avoid that conversion step. Was there some way of pre-generating the SVGs on the server rather than doing it all on the client?

In theory, yes. I could spin up a headless browser, run the JavaScript and take a snapshot. But that’s a bit beyond my backend programming skills, so I’ve taken a slightly different approach.

The first time anyone hits a tune page, the ABCs getting converted to SVGs as usual. But now there’s one additional step. I grab the generated markup and send it as an Ajax payload to an endpoint on my server. That endpoint stores the sheetmusic as a file in a cache.

Next time someone hits that page, there’s a server-side check to see if the sheetmusic has been cached. If it has, send that down the wire embedded directly in the HTML.

The idea is that over time, most of the sheetmusic on the site will transition from being generated in the browser to being stored on the server.

So far it’s working out well.

Take a really popular tune like The Lark In The Morning. There are twenty settings, and each one has four parts. Previously that would have resulted in a few seconds of parsing and rendering time on the main thread. Now everything is delivered up-front.

I’m not out of the woods. A page like that with lots of sheetmusic and plenty of comments is going to have a hefty page weight and a large DOM size. I’ve still got a fair bit of main-thread work happening, but now the bulk of it is style and layout, whereas previously I had the JavaScript overhead on top of that.

I’ll keep working on it. But overall, the speed improvement is great. A typical tune page is now very speedy indeed.

It’s like a microcosm of web performance in general: respect your users’ time, network connection and battery life. If that means shifting the work from the browser to the server, do it!

Reckoning: Part 1 — The Landscape - Infrequently Noted

I want to be a part of a frontend culture that accepts and promotes our responsibilities to others, rather than wallowing in self-centred “DX” puffery. In the hierarchy of priorities, users must come first.

Alex doesn’t pull his punches in this four-part truth-telling:

1. The Landscape
2. Object Lesson
3. Caprock
4. The Way Out

The React anti-pattern of hugely bloated single-page apps has to stop. And we can stop it.

Success or failure is in your hands, literally. Others in the equation may have authority, but you have power.

Begin to use that power to make noise. Refuse to go along with plans to build YAJSD (Yet Another JavaScript Disaster). Engineering leaders look to their senior engineers for trusted guidance about what technologies to adopt. When someone inevitably proposes the React rewrite, do not be silent. Do not let the bullshit arguments and nonsense justifications pass unchallenged. Make it clear to engineering leadership that this stuff is expensive and is absolutely not “standard”.

Every website and web app should have a service worker | Go Make Things

Needless to say, I agree with this sentiment.

I’ve worked with a lot of browser technology over the years. Service workers are pretty mind-blowing.

Faster Connectivity !== Faster Websites - Jim Nielsen’s Blog

The bar to overriding browser defaults should be way higher than it is.

Amen!

Standing still - a performance tinker | Trys Mudford

What Trys describes here mirrors my experience too—it really is worth occasionally taking a little time to catch the low-hanging fruit of your site’s web performance (and accessibility):

I’ve shaved nearly half a megabyte off the page size and improved the accessibility along the way. Not bad for an evening of tinkering.

What Is A Single-page Application?: HeydonWorks

You can’t create a complex modern web application like Google Mail without JavaScript and a SPA architecture. Google Mail is a webmail client and webmail clients existed some time before JavaScript became the language it is today or frameworks like Angular JS or Angular BS existed. However, you cannot create a complex modern web application like Google Mail without JavaScript. Google Mail itself offers a basic HTML version that works perfectly well without JavaScript of any form—let alone a 300KB bundle. But, still, you cannot create a complex modern web application like Google Mail without JavaScript. Just keep saying that. Keep repeating that line in perpetuity. Keep adding more and more JavaScript and calling it good.