Tags: bugs

12

sparkline

Sunday, October 28th, 2018

Phil Nash and Jeremy Keith Save the Safari Video Playback Day

I love this example of paying it forward:

Friday, October 26th, 2018

Service workers and videos in Safari

Alright, so I’ve already talked about some gotchas when debugging service worker issues. But what if you don’t even realise the problem has anything to do with your service worker?

This is not a hypothetical situation. I encountered this very thing myself. Gather ‘round the campfire, children…

One of the latest case studies on the Clearleft site is a nice write-up by Luke of designing a mobile app for Virgin Holidays. The case study includes a lovely video that demonstrates the log-in flow. I implemented that using a video element (with a poster image). Nice and straightforward. Super easy. All good.

But I hadn’t done my due diligence in browser testing (I guess I didn’t even think of it in this case). Hana informed me that the video wasn’t working at all in Safari. The poster image appeared just fine, but when you clicked on it, the video didn’t load.

I ducked, ducked, and went, uncovering what appeared to be the root of the problem. It seems that Safari is fussy about having servers support something called “byte-range requests”.

I had put the video in question on an Amazon S3 server. I came to the conclusion that S3 mustn’t support these kinds of headers correctly, or something.

Now I had a diagnosis. The next step was figuring out a solution. I thought I might have to move the video off of S3 and onto a server that I could configure a bit more.

Luckily, I never got ‘round to even starting that process. That’s good. Because it turns out that my diagnosis was completely wrong.

I came across a recent post by Phil Nash called Service workers: beware Safari’s range request. The title immediately grabbed my attention. Safari: yes! Video: yes! But service workers …wait a minute!

There’s a section in Phil’s post entitled “Diagnosing the problem”, in which he says:

I first thought it could have something to do with the CDN I’m using. There were some false positives regarding streaming video through a CDN that resulted in some extra research that was ultimately fruitless.

That described my situation exactly. Except Phil went further and nailed down the real cause of the problem:

Nginx was serving correct responses to Range requests. So was the CDN. The only other problem? The service worker. And this broke the video in Safari.

Doh! I hadn’t even thought about service workers!

Phil came up with a solution, and he has kindly shared his code.

I decided to go for a dumber solution:

if ( request.url.match(/\.(mp4)$/) ) {
  return;
}

That tells the service worker to just step out of the way when it comes to video requests. Now the video plays just fine in Safari. It’s a bit of a shame, because I’m kind of penalising all browsers for Safari’s bug, but the Clearleft site isn’t using much video at all, and in any case, it might be good not to fill up the cache with large video files.

But what’s more important than any particular solution is correctly identifying the problem. I’m quite sure I never would’ve been able to fix this issue if Phil hadn’t gone to the trouble of sharing his experience. I’m very, very grateful that he did.

That’s the bigger lesson here: if you solve a problem—even if you think it’s hardly worth mentioning—please, please share your solution. It could make all the difference for someone out there.

Service workers and browser extensions

I quite enjoy a good bug hunt. Just yesterday, myself and Cassie were doing some bugfixing together. As always, the first step was to try to reproduce the problem and then isolate it. Which reminds me…

There’ve been a few occasions when I’ve been trying to debug service worker issues. The problem is rarely in reproducing the issue—it’s isolating the cause that can be frustrating. I try changing a bit of code here, and a bit of code there, in an attempt to zero in on the problem, butwith no luck. Before long, I’m tearing my hair out staring at code that appears to have nothing wrong with it.

And that’s when I remember: browser extensions.

I’m currently using Firefox as my browser, and I have extensions installed to stop tracking and surveillance (these technologies are usually referred to as “ad blockers”, but that’s a bit of a misnomer—the issue isn’t with the ads; it’s with the invasive tracking).

If you think about how a service worker does its magic, it’s as if it’s sitting in the browser, waiting to intercept any requests to a particular domain. It’s like the service worker is the first port of call for any requests the browser makes. But then you add a browser extension. The browser extension is also waiting to intercept certain network requests. Now the extension is the first port of call, and the service worker is relegated to be next in line.

This, apparently, can cause issues (presumably depending on how the browser extension has been coded). In some situations, network requests that should work just fine start to fail, executing the catch clauses of fetch statements in your service worker.

So if you’ve been trying to debug a service worker issue, and you can’t seem to figure out what the problem might be, it’s not necessarily an issue with your code, or even an issue with the browser.

From now on when I’m troubleshooting service worker quirks, I’m going to introduce a step zero, before I even start reproducing or isolating the bug. I’m going to ask myself, “Are there any browser extensions installed?”

I realise that sounds as basic as asking “Are you sure the computer is switched on?” but there’s nothing wrong with having a checklist of basic questions to ask before moving on to the more complicated task of debugging.

I’m going to make a checklist. Then I’m going to use it …every time.

Tuesday, August 7th, 2018

Coming to a browser near you - faster than ever before!

A great long-term perspective from Rachel on the pace of change in standards getting shipped in browsers:

The pace that things are shipping, and at which bugs are fixed is like nothing we have seen before. I know from sitting around a table with representatives from each browser vendor at the CSS Working Group how important interop is. No-one wants features to be implemented differently in browsers. This is what we were asking for with WaSP, and despite the new complexity of the platform, browsers rendering standard features in different ways is becoming increasingly rare. Bugs happen, sometimes in the browser and sometimes in the spec, but there is a commitment to avoid these and to create a stable platform we can all rely on. It is exciting to be part of it.

Saturday, June 23rd, 2018

I discovered a browser bug - JakeArchibald.com

Jake’s blow-by-blow account of uncovering a serious browser vulnerability is fascinating. But if you don’t care for the technical details, skip ahead to to how different browser makers handled the issue—it’s very enlightening. (And if you do care for the technical details, make sure you click on the link to the PDF version of this post.)

Sunday, March 4th, 2018

The People Part of Design Systems – Related Works – Medium

I like the idea of “design bugs”:

Every two weeks or so, a group of designers would get together for a couple of hours to fix what we called “design bugs.” These were things that didn’t hinder functionality and wouldn’t have been filed as an engineering bug, but were places where we were using an old component, an existing one incorrectly, or a one-off alteration.

Monday, July 31st, 2017

rachelandrew/gridbugs: A curated list of Grid interop issues

Rachel is maintaining this (short) list of browser bugs with CSS Grid, inspired by the excellent Flexbugs.

Grid shipped into browsers](https://gridbyexample.com/browsers) in a highly interoperable state, however there are a few issues - let’s document any we find here.

Monday, December 7th, 2015

philipwalton/flexbugs

A list of known bugs (and workarounds) in flexbox implementations. This is going to be handy to refer back to.

Wednesday, April 23rd, 2014

webcompat.com

I like this idea. It would be nice to see it catch on…

  1. Report a bug for any website or browser.
  2. Our team of volunteers diagnoses the bug.
  3. We send a fix to the site owner or browser.

Friday, March 23rd, 2012

scottjehl/Device-Bugs

Scott has created a one-stop-shop for documenting browser bugs in mobile devices. Feel free to add to it.

Friday, May 14th, 2010

New Programming Jargon — Global Nerdy

Some of the best neologisms in programming, many of them to do with bug-fixing.

Thursday, December 4th, 2008

Welcome | Sifter

Garrett has launched his bug-tracking web app. Looks lovely.