Destroying an angular app

[shahata]

I've been playing around this weekend with a project that I've been meaning to open source for a while now: https://github.com/shahata/angular-widget

In a nutshell, it let's you create many "widgets" in a single page, each widget is lazy loaded and has it's own injector and all of them live together nicely in one page. Demo at: http://shahata.github.io/angular-widget/#

When you click "add..." a widget is added, and when you click "del" it is destroyed. I'm no performance expert, but if I look in developer tools I see that destroyed widgets are cleaned up nicely.

The problem is, that if I add a "bad" widget it does not get cleaned up so nicely. What's bad about this widget? Well, it uses $cookies. $cookies polls the browser's cookie storage every 100ms to check if cookies were updated. It start to poll when it is created and stop... well, never. So if I add many "bad" widgets, I have many polling timeouts of $cookies and even if I remove all the widgets polling continues, and I guess also prevents GC.

I would like to try and add a mechanism for destroying angular apps in order to deal with this kind of issues. If this is something desirable for angular, I can take this PR. The design I have in mind is that users will be able to call injector.$destroy() and the injector will then call $destroy on every injectable that has a $destroy method which in turn will cancel any pending actions like timeouts, intervals, http requests, etc.

$rootScope obviously already has a $destroy method, though it is a bit partial - see #7564

[shahata]

Here is what the devtools look like after adding many "regular" widgets and then removing them (good) and then adding many "bad" wodgets and then removing them (not so good):

[thebigredgeek]

I personally think angular-cookies needs a massive refactor. Honestly, we should be using getters/setters instead of constant polling. This is a huge waste of battery life on mobile. And the new direction is Mobile First!

[caitp]

@thebigredgeek please direct your attention to Angular v2.0.0 for all your mobile-first needs, that's really the place where we can rely on ES5 at least existing

[shahata]

Just to make sure there is no confusion - this issue is NOT about cookies and NOT about mobile. It is about destruction of apps/injectors.

[btford]

@shahata the problem is that all 3rd-party services would also potentially need to implement this.

For your case, I think a pragmatic approach would be to roll-your-own cookies service that doesn't involve polling.

Angular 1.x currently doesn't have a way to destroy services. I don't think there's a good way to add this type of feature that's aligned with the current Angular app lifecycle.

[shahata]

@btford yes, this is similar to how we expect directives to element.on('$destroy', ...) if they have any cleanup to perform. I think we can expect services to implement a $destory method if they need to cleanup.

[btford]

@shahata do you have any other specific services that poll?

I think this idea is interesting, but my gut feeling is that it's going to be more trouble than it's worth.

See also #6180.

[shahata]

@btford I have many "widgets" written for this angular-widget framework and I'm pretty sure polling will be required for some of them. Since we currently develop widgets only internally I can probably workaround this with some patch, but I think it is better to solve this the proper way.

If you think that it is interesting, I will send a PR for this. Otherwise, probably not a big deal.

[thebigredgeek]

@shahata you can't simple use events?

[shahata]

This will probably be solved by #8005