Tags: service

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Wednesday, April 27th, 2022

Trust

I’ve noticed a strange mindset amongst front-end/full-stack developers. At least it seems strange to me. But maybe I’m the one with the strange mindset and everyone else knows something I don’t.

It’s to do with trust and suspicion.

I’ve made no secret of the fact that I’m suspicious of third-party code and dependencies in general. Every dependency you add to a project is one more potential single point of failure. You have to trust that the strangers who wrote that code knew what they were doing. I’m still somewhat flabbergasted that developers regularly add dependencies—via npm or yarn or whatever—that then pull in even more dependencies, all while assuming good faith and competence on the part of every person involved.

It’s a touching expression of faith in your fellow humans, but I’m not keen on the idea of faith-based development.

I’m much more trusting of native browser features—HTML elements, CSS features, and JavaScript APIs. They’re not always perfect, but a lot of thought goes into their development. By the time they land in browsers, a whole lot of smart people have kicked the tyres and considered many different angles. As a bonus, I don’t need to install them. Even better, end users don’t need to install them.

And yet, the mindset I’ve noticed is that many developers are suspicious of browser features but trusting of third-party libraries.

When I write and talk about using service workers, I often come across scepticism from developers about writing the service worker code. “Is there a library I can use?” they ask. “Well, yes” I reply, “but then you’ve got to understand the library, and the time it takes you to do that could be spent understanding the native code.” So even though a library might not offer any new functionality—just a different idion—many developers are more likely to trust the third-party library than they are to trust the underlying code that the third-party library is abstracting!

Developers are more likely to trust, say, Bootstrap than they are to trust CSS grid or custom properties. Developers are more likely to trust React than they are to trust web components.

On the one hand, I get it. Bootstrap and React are very popular. That popularity speaks volumes. If lots of people use a technology, it must be a safe bet, right?

But if we’re talking about popularity, every single browser today ships with support for features like grid, custom properties, service workers and web components. No third-party framework can even come close to that install base.

And the fact that these technologies have shipped in stable browsers means they’re vetted. They’ve been through a rigourous testing phase. They’ve effectively got a seal of approval from each individual browser maker. To me, that seems like a much bigger signal of trustworthiness than the popularity of a third-party library or framework.

So I’m kind of confused by this prevalent mindset of trusting third-party code more than built-in browser features.

Is it because of the job market? When recruiters are looking for developers, their laundry list is usually third-party technologies: React, Vue, Bootstrap, etc. It’s rare to find a job ad that lists native browser technologies: flexbox, grid, service workers, web components.

I would love it if someone could explain why they avoid native browser features but use third-party code.

Until then, I shall remain perplexed.

Wednesday, April 20th, 2022

Thursday, February 24th, 2022

How to make MPAs that are as fast as SPAs | Go Make Things

The headline is a little misleading because if you follow this advice, your multi-page apps will be much much faster than single page apps, especially when you include that initial page load of a single page app.

Here’s a quick high-level summary of what I do…

  1. Serve pre-rendered, mostly static HTML.
  2. Inline everything, including CSS and JavaScript.
  3. Use mostly platform-native JavaScript, and as little of it as possible.
  4. Minify and gzip all the things.
  5. Lean heavily on service workers.

That’s an excellent recipe for success right there!

Wednesday, December 29th, 2021

Add a Service Worker to Your Site | CSS-Tricks - CSS-Tricks

Damn, I wish I had thought of giving this answer to the prompt, “What is one thing people can do to make their website better?”

If you do nothing else, this will be a huge boost to your site in 2022.

Chris’s piece is a self-contained tutorial!

Monday, December 13th, 2021

Serve folder for web development

This is a very nifty use of a service worker—choose a local folder that you want to navigate using HTTP rather than the file system.

Thursday, October 7th, 2021

Getting Started with PWAs [Workshop]

The slides from Aaron’s workshop at today’s PWA Summit. I really like the idea of checking navigator.connection.downlink and navigator.connection.saveData inside a service worker to serve different or fewer assets!

Monday, September 20th, 2021

11ty/api-indieweb-avatar: Return an optimized avatar image from a domain name input.

Here’s a nifty little service from Zach: pass in a URL and it returns an image of the site’s icon.

Here’s mine.

Think of it as the indie web alternative to showing Twitter avatars.

Sunday, June 6th, 2021

Let’s talk about failure

Denise shares a cautionary tale of service design gone wrong.

Thursday, April 22nd, 2021

Full Stack Service Design – Sarah Drummond

Katie shared this (very good) piece about service design on Slack at work today, and when I got to the bit about different levels, my brain immediately went “pace layers!”

  1. The Service
  2. The Infrastructure
  3. The Organisation
  4. The Intent
  5. The Culture

Tuesday, March 23rd, 2021

Service worker weirdness in Chrome

I think I’ve found some more strange service worker behaviour in Chrome.

It all started when I was checking out the very nice new redesign of WebPageTest. I figured while I was there, I’d run some of my sites through it. I passed in a URL from The Session. When the test finished, I noticed that the “screenshot” tab said that something was being logged to the console. That’s odd! And the file doing the logging was the service worker script.

I fired up Chrome (which isn’t my usual browser), and started navigating around The Session with dev tools open to see what appeared in the console. Sure enough, there was a failed fetch attempt being logged. The only time my service worker script logs anything is in the catch clause of fetching pages from the network. So Chrome was trying to fetch a web page, failing, and logging this error:

The service worker navigation preload request failed with a network error.

But all my pages were loading just fine. So where was the error coming from?

After a lot of spelunking and debugging, I think I’ve figured out what’s happening…

First of all, I’m making use of navigation preloads in my service worker. That’s all fine.

Secondly, the website is a progressive web app. It has a manifest file that specifies some metadata, including start_url. If someone adds the site to their home screen, this is the URL that will open.

Thirdly, Google recently announced that they’re tightening up the criteria for displaying install prompts for progressive web apps. If there’s no network connection, the site still needs to return a 200 OK response: either a cached copy of the URL or a custom offline page.

So here’s what I think is happening. When I navigate to a page on the site in Chrome, the service worker handles the navigation just fine. It also parses the manifest file I’ve linked to and checks to see if that start URL would load if there were no network connection. And that’s when the error gets logged.

I only noticed this behaviour because I had specified a query string on my start URL in the manifest file. Instead of a start_url value of /, I’ve set a start_url value of /?homescreen. And when the error shows up in the console, the URL being fetched is /?homescreen.

Crucially, I’m not seeing a warning in the console saying “Site cannot be installed: Page does not work offline.” So I think this is all fine. If I were actually offline, there would indeed be an error logged to the console and that start_url request would respond with my custom offline page. It’s just a bit confusing that the error is being logged when I’m online.

I thought I’d share this just in case anyone else is logging errors to the console in the catch clause of fetches and is seeing an error even when everything appears to be working fine. I think there’s nothing to worry about.

Update: Jake confirmed my diagnosis and agreed that the error is a bit confusing. The good news is that it’s changing. In Chrome Canary the error message has already been updated to:

DOMException: The service worker navigation preload request failed due to a network error. This may have been an actual network error, or caused by the browser simulating offline to see if the page works offline: see https://w3c.github.io/manifest/#installability-signals

Much better!

Thursday, March 18th, 2021

Now THAT’S What I Call Service Worker! – A List Apart

This is terrific! Jeremy shows how you can implement a fairly straightforward service worker for performance gains, but then really kicks it up a notch with a recipe for turning a regular website into a speedy single page app without framework bloat.

Thursday, March 11th, 2021

When service workers met framesets

Oh boy, do I have some obscure browser behaviour for you!

To set the scene…

I’ve been writing here in my online journal for almost twenty years. The official anniversary will be on September 30th. But this website has been even online longer than that, just in a very different form.

Here’s the first version of adactio.com.

Like a tour guide taking you around the ruins of some lost ancient civilisation, let me point out some interesting features:

  • Observe the .shtml file extension. That means it was once using Apache’s server-side includes, a simple way of repeating chunks of markup across pages. Scientists have been trying to reproduce the wisdom of the ancients using modern technology ever since.
  • See how the layout is 100vw and 100vh? Well, this was long before viewport units existed. In fact there is no CSS at all on that page. It’s one big table element with 100% width and 100% height.
  • So if there’s no CSS, where is the border-radius coming from? Let me introduce you to an old friend—the non-animated GIF. It’s got just enough transparency (though not proper alpha transparency) to fake rounded corners between two solid colours.
  • The management takes no responsibility for any trauma that might befall you if you view source. There you will uncover JavaScript from the dawn of time; ancient runic writing like if (navigator.appName == "Netscape")

Now if your constitution was able to withstand that, brace yourself for what happens when you click on either of the two links, deutsch or english.

You find yourself inside a frameset. You may also experience some disorienting “DHTML”—the marketing term given to any combination of JavaScript and positioning in the late ’90s.

Note that these are not iframes, they are frames. Different thing. You could create single page apps long before Ajax was a twinkle in Jesse James Garrett’s eye.

If you view source, you’ll see a React-like component system. Each frameset component contains frame components that are isolated from one another. They’re like web components. Each frame has its own (non-shadow) DOM. That’s because each frame is actually a separate web page. If you right-click on any of the frames, your browser should give the option to view the framed document in its own tab or window.

Now for the part where modern and ancient technologies collide…

If you’re looking at the frameset URL in Firefox or Safari, everything displays as it should in all its ancient glory. But if you’re looking in Google Chrome and you’ve visited adactio.com before, something very odd happens.

Each frame of the frameset displays my custom offline page. The only way that could be served up is through my service worker script. You can verify this by opening the framest URL in an incognito window—everything works fine when no service worker has been registered.

I have no idea why this is happening. My service worker logic is saying “if there’s a request for a web page, try fetching it from the network, otherwise look in the cache, otherwise show an offline page.” But if those page requests are initiated by a frame element, it goes straight to showing the offline page.

Is this a bug? Or perhaps this is the correct behaviour for some security reason? I have no idea.

I wonder if anyone has ever come across this before. It’s a very strange combination of factors:

  • a domain served over HTTPS,
  • that registers a service worker,
  • but also uses framesets and frames.

I could submit a bug report about this but I fear I would be laughed out of the bug tracker.

Still …the World Wide Web is remarkable for its backward compatibility. This behaviour is unusual because browser makers are at pains to support existing content and never break the web.

Technically a modern website (one that registers a service worker) shouldn’t be using deprecated technology like frames. But browsers still need to be able support those old technologies in order to render old websites.

This situation has only arisen because the same domain—adactio.com—is host to a modern website and a really old one.

Maybe Chrome is behaving strangely because I’ve built my online home on ancient burial ground.

Update: Both Remy and Jake did some debugging and found the issue…

It’s all to do with navigation preloads and the value of event.preloadResponse, which I believe is only supported in Chrome which would explain the differences between browsers.

According to this post by Jake:

event.preloadResponse is a promise that resolves with a response, if:

  • Navigation preload is enabled.
  • The request is a GET request.
  • The request is a navigation request (which browsers generate when they’re loading pages, including iframes).

Otherwise event.preloadResponse is still there, but it resolves with undefined.

Notice that iframes are mentioned, but not frames.

My code was assuming that if event.preloadRepsonse exists in my block of code for responding to page requests, then there’d be a response. But if the request was initiated from a frameset, it is a request for a page and event.preloadRepsonse does exist …but it’s undefined.

I’ve updated my code now to check this assumption (and fall back to fetch).

This may technically still be a bug though. Shouldn’t a page loaded from a frameset count as a navigation request?

Thursday, October 15th, 2020

Progressier | Make your website a PWA in 42 seconds

This in an intriguing promise (there’s no code yet):

A PWA typically requires writing a service worker, an app manifest and a ton of custom code. Progressier flattens the learning curve. Just add it to your html template — you’re done.

I worry that this one line of code will pull in many, many, many, many lines of JavaScript.

Tuesday, September 29th, 2020

Building a client side proxy

This is a great way to use a service worker to circumvent censorship:

After the visitor opens the website once over a VPN, the service worker is downloaded and installed. The VPN can then be disabled, and the service worker will take over to request content from non-blocked servers, effectively acting as a proxy.

Thursday, August 20th, 2020

Service Workers | Go Make Things

Chris Ferdinandi blogs every day about the power of vanilla JavaScript. For over a week now, his daily posts have been about service workers. The cumulative result is this excellent collection of resources.

Saturday, August 1st, 2020

The amazing power of service workers | Go Make Things

So, why would you want to use a service worker? Here are some cool things you can do with it.

Chris lists some of the ways a service worker can enhance user experience.

Monday, July 20th, 2020

Always at Your Service · Matthias Ott – User Experience Designer

Thoughts on user experience design and service design, prompted by the Clearleft podcast:

I especially enjoyed the latest episode about a topic that has become a bit of a hyped buzzword over the last few years: Service design.

Rich with anecdotes and stories, the episode started with an investigation: What is service design, anyway?

Saturday, July 18th, 2020

Indexing your offline-capable pages with the Content Indexing API

A Chrome-only API for adding offline content to an index that can be exposed in Android’s “downloads” list. It just shipped in the lastest version of Chrome.

I’m not a fan of browser-specific non-standards but you can treat this as an enhancement—implementing it doesn’t harm non-supporting browsers and you can use feature detection to test for it.

Works offline

How do we tell our visitors our sites work offline? How do we tell our visitors that they don’t need an app because it’s no more capable than the URL they’re on right now?

Remy expands on his call for ideas on branding websites that work offline with a universal symbol, along the lines of what we had with RSS.

What I’d personally like to see as an outcome: some simple iconography that I can use on my own site and other projects that can offer ambient badging to reassure my visitor that the URL they’re visiting will work offline.