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!

JavaScript broke the web (and called it progress) - Jono Alderson

Semantic HTML? Optional. Server-side rendering? Rebuilt from scratch. Accessibility? Maybe, if there’s time. Performance? Who cares, when you can save costs by putting loading burdens onto the user’s device, instead of your server?

So gradually, the web became something you had to compile before you could publish. Not because users needed it. But because developers wanted it to feel modern.

Everything’s optimised for developers – and hostile to everyone else.

This isn’t accidental. It’s cultural. We’ve created an industry where complexity is celebrated. Where cleverness is rewarded. Where engineering sophistication is valued more than clarity, usability, or commercial effectiveness.

Who’s Afraid of a Hard Page Load?

Why single-page apps are just not worth it:

Here’s the problem: your team almost certainly doesn’t have what it takes to out-engineer the browser. The browser will continuously improve the experience of plain HTML, at no cost to you, using a rendering engine that is orders of magnitude more efficient than JavaScript.

Meanwhile, the browser marches on, improving the UX of every website that uses basic HTML semantics. For instance: browsers often don’t repaint full pages anymore.

Stop Using and Recommending React - Lusitos Tech Blog

I can’t recommend React to any project or customer anymore.

Using almost any other modern alternative, you will save time, money and nerves, even if you haven’t used them before.

Don’t stick to technology just because you know it.

Build for the Web, Build on the Web, Build with the Web – Web Performance and Site Speed Consultant

If I was only able to give one bit of advice to any company: iterate quickly on a slow-moving platform.

Excellent advice from Harry (who first cast his pearls before the swine of LinkedIn but I talked him ‘round to posting this on his own site).

1. Opt into web platform features incrementally
2. Embrace progressive enhancement to build fast, reliable applications that adapt to your customers’ context
3. Write code that leans into the browser, not away from it

I’m not against front-end frameworks, and, believe me, I’m not naive enough to believe that the only thing a front-end framework provides is soft navigations, but if you’re going to use one, I shouldn’t be able to smell it.

Moving on from React, a Year Later

Many interactions are not possible without JavaScript, but that doesn’t mean we should look to write more than we have to. The server doing something useful is a requirement for building an interesting business. The client doing something is often a nice-to-have.

There’s also this:

It’s really fast

One of the arguments for a SPA is that it provides a more reactive customer experience. I think that’s mostly debunked at this point, due to the performance creep and complexity that comes in with a more complicated client-server relationship.