Service Workers

by andRyanMiller • 8 years ago

126 66 8 years ago

sbr4643• 8 years ago

Great write up. I’ve been exploring SWs recently to help with downloading and caching data in the background for faster UI.

Question, I’d like to avoid doing large downloads or possibly cap the transfer rate to avoid any potential jank. Is there a best practice or is it possible to monitor the current browser interaction to determine how strategically best to pull data with a SW?

Depending on what a user chooses to cache, it’s JSON data (1-10MB) going to a mix of localstorage and indexedDB.

slow_donkey• 8 years ago

Have you looked into using a fetch event hook? The first thing I thought of was an Axios interceptor if you're using Axios or other http lib.

That should allow you to sum up download sizes.

wbercx• 8 years ago

Thanks for this! I've recently been asked how much data our React Native app uses. I totally hadn't thought of using Axios' interceptors to track this. So obvious!

pmlnr9• 8 years ago

May I ask the justification to download 1-10MB JSON on the user's system without the user being aware?

ahsanejaz2• 8 years ago

You also cache regular web resources like images. It is for the user's benefit since next visit to the site can be faster.

sbr4643• 8 years ago

They are aware, it’s business software, syncing records/templates/frequent info etc. It’s only to improve the experience, and it’s controlled by settings/opt-in etc.

It’s also configurable to only operate on faster connections/non mobile IP address etc.

The main reason I was asking is if you currently benchmark service worker updates with indexedDB for async/larger updates, they still cause a small amount of jank, (at least on larger requests) even though they may use a different process etc.

There’s a github repo with a benchmark, this link is older but if you clone the current version and update to the lastest packages, the results are still similar.

  https://www.google.com/amp/s/nolanlawson.com/2015/09/29/indexeddb-websql-localstorage-what-blocks-the-dom/amp/

michaelmrose3• 8 years ago

"Imagine being able to respond to push notifications, intercept resource requests, and schedule background syncronization, all without the need for a user to actively have your website open in front of them."

".. by authoring special-purpose JavaScript which you register with the browser."

Why does this seem like something useful for malware and generally annoying me.

Brakenshire• 8 years ago

Push requests only exists on Chrome and is behind a permission, intercepting resource requests within the domain of a website could cause some annoyances, can’t see the malware effect immediately. Scheduling a download for a stable connection, again, could be an annoyance, but what’s the malware implication?

chrismorgan4• 8 years ago

The malware angle is basically service-worker-powered cache poisoning: if you can get the server to serve your code once, users can get a service worker installed, and intercept resource requests under that path. It’s limited in practical value because you have to be able to serve a full JS file as the service worker, rather than just injecting a snippet of JS as the most common technique is, but it is a genuine attack vector.

michaelmrose3• 8 years ago

People are bad at managing permissions. Making people's security depend on responding reasonably to a dialog box nearly always ends in tears.

If I popped up a dialog box asking to harvest a kidney 30% of users would click yes.

fungi• 8 years ago

Open up about:serviceworkers and observe the wonders of cookies 2.0

Kinda sucks that something with such promise is predominantly used as just another weapon for tracking.

JeremyBanks• 8 years ago

Service Workers isn't a new persistence mechanism, it uses existing ones.

Khaine• 8 years ago

Most new web features seem to enable malware and other scummy thing all to promote the web as an app platform.

I would we rather leave http to be a document model, and create something new and better to support"web-based" apps.

dannyw2• 8 years ago

I like service workers, but I don't like the lack of control I have.

For example, I want Messenger to send me notifications if I have the tab open, but I don't want the service worker to maintain a persistent connection and send me notifications with the tab closed.

Unfortunately, I am not able to block service workers. My only option is to block notifications entirely, which doesn't even stop the service worker.

ahsanejaz2• 8 years ago

The service worker does not maintain a persistent connection. Some websites/pwa's allow you to configure that.

bryanrasmussen3• 8 years ago

but then you're depending on the website/pwa to be a good citizen and allow you to configure that

dannyw2• 8 years ago

The service worker should not be allowed to listen to global-push notifications without me telling it to.

The notifications dropdown should be:

- Always allow

- Allow when open

- Disallow

amelius• 8 years ago

I suppose that depends on the type of browser you use.

untog3• 8 years ago

The service worker can't maintain a persistent connection. Without an active tab it is shut down after 30 seconds or so. It can receive events via the Push API, which is what you're seeing. But if you refuse notification permissions the site cannot use the Push API. I'm actually not sure how it works when you block notifications after having given permission - it's a requirement that you show a notification in response to a push, so if you're blocked, I'm not sure how the browser registers it.

More broadly, I agree that it is strange you can opt into the Push API without a permission prompt. I wish it weren't the case, but I do think it would be confusing to users to request separate push and notification permissions - most consider them to be synonymous, even if they aren't.

nerdponx2• 8 years ago

How much would I have to donate to Mozilla in order to get them to develop a service worker management UI in Firefox?

karolg• 8 years ago

Actually, Firefox has UI for this. Click "Menu -> Web Developer -> Service Workers". This will open a special page "about:debugging#workers". It shows active service workers and allows you to unregister them. There is another even simpler UI at "about:serviceworkers".

pmlnr9• 8 years ago

Firefox:

    about:config 
    dom.serviceWorkers.enabled;false

Why:

They bite. The generic idea may even be reasonable (offline working web app), but every single time I encounter service workers they make things worse.

If you load a React frontend, it'll, by default, deploy a service worker. Good luck trying to load anything non-react from that resource/server.

I never asked for a web app to work in the background once I closed a site. Nobody should be trained to expect websites work in the background - that is not how they are. If there is no tab open, there should be no notification, no nothing. That is how the web works.

wakeywakeywakey3• 8 years ago

If you load a React frontend, it'll, by default, deploy a service worker.

What?

That is how the web works.

The web 'experience' has stopped being about fetching static documents in a request/response fashion long ago. Consumers demand rich apps and interactivity, and it appears they're having it their way.

pmlnr9• 8 years ago

What?

https://github.com/facebook/create-react-app/issues/2398

Consumers demand rich apps and interactivity

They really don't. That's an assumption without data.

EDIT: see gov.uk. It works quite well without being fancy.

htor2• 8 years ago

Consumers demand rich apps and interactivity, and it appears they're having it their way.

no consumer ever demanded the web to be like an app. this is marketing baloney crap. stop treating humans browsing the web as targets for advertisement and consumerism.

htor2• 8 years ago

That is how the web works.

good luck trying to convince google of that. they are shaping the web just the way they want it. push notifications? nobody ever except the marketing apartment thought that was a good idea to add to anything. if we try making everything on the web like mobile apps we're gonna get garbage features like this and false expectations on what the web should be like.

LeanderK• 8 years ago

Well, i was looking foreward to push-notifications on the web and used them for non-marketing related purposes.

EDIT: I also used Service-Workers in the same project to provide offline functionality :) It worked great, I was suprised how good it worked!

bryanrasmussen3• 8 years ago

I'm pretty sure that everyone who ever used some sort of messaging application thinks that push notifications are a good idea.

Vinnl• 8 years ago

If you load a React frontend, it'll, by default, deploy a service worker.

I think you mean that create-react-app is doing this by default, and that it might be a surprise and cause of problems for the developer. Which is also the reason why they're removing that by default from create-react-app v2.

That is how the web works.

That's not really an argument, in that it also could've been used as an argument against the introduction of inline images, CSS, or anything added to the web after its first publication. It doesn't really matter how the web works today; what's relevant is how we want the web to work.

chrismorgan4• 8 years ago

My most delightful experience with a service worker was SVGOMG, https://jakearchibald.github.io/svgomg/. One time I was without an internet connection, and I thought to myself, “if only it had a service worker so it’d work offline!” and then I opened a tab to it, to remind myself to optimise the SVG I was working with later, and— huh. It loaded. On reflection, I decided that given who Jake Archibald is, it made sense that he’d be an early service worker adopter. So that day I was really pleased with the Just Works™ value of that service worker.

And SVGOMG is able to load faster thanks to service workers, too.

At FastMail, we’ll be getting round to adding service workers some time soon, and it’ll actually give us a quite fascinating performance boost: even without supporting full offlineness, simply caching the basic data you need can get you to the point where you need literally no requests before you can load the interface, showing meaningful data to the user, and then fetch updated data in the background. I’m confident we’ll be able to get startup time to under two seconds with service workers for code and data loading/caching, and hopeful that we’ll get it down to under a second.

Service workers can be badly implemented, but they also offer the possibility of some quite delightful improvements in websites and web apps.

pmlnr9• 8 years ago

I've recently set an offline mail client to sync mail locally for my wife's laptop. Her two gmail accounts downloaded 22GB.

Be careful what offline actually means when it comes to mail; eg. that 22GB as service worker cache sounds a bit nasty to me, especially because service workers don't tend to differentiate between desktop and mobile.

untog3• 8 years ago

every single time I encounter service workers they make things worse

I'd wager you encounter more service workers than you think, but you don't notice them when they work correctly. They are designed to be invisible in the majority of cases, so of course you only notice them when something goes wrong.

baybal2• 8 years ago

I'm very glad about existence of this wonderful extension: https://chrome.google.com/webstore/detail/manage-web-workers...

mellett68• 8 years ago

Web workers and service workers do different things

werdnapk• 8 years ago

Note to Author: Irregardless is not a word.

bluntfang• 8 years ago

Yes, it is.

https://www.merriam-webster.com/dictionary/irregardless

phkahler• 8 years ago

It's a crappy word then.

RegBarclay• 8 years ago

"Use regardless instead."

camflan• 8 years ago

Webster’s is a descriptive dictionary, which will include nonstandard words so that it can _describe_ them, and provide guidance on what should be used instead. Just like in that link - it suggests the use of “regardless”

eletious• 8 years ago

Maybe I'm out of touch, but for messaging apps wouldn't it be desirable to have an actual service from a native app that you can enable/disable in your OS?

Ajedi32• 8 years ago

On some platforms, progressive web apps effectively _are_ native: https://developers.google.com/web/fundamentals/integration/w...

c0brac0bra• 8 years ago

"Imagine being able to respond to push notifications"

Yes, wouldn't it be wonderful if we could do this in all major browsers today? sigh

Service Workers

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