[dojo-contributors] Dojo 1.9 Proposal
neonstalwart at gmail.com
Tue Oct 16 19:27:37 EDT 2012
i'd agree that IndexedDB is a better target for this kind of thing but unfortunately right now browser support for IndexedDB is limited to FF and chrome with support coming soon in IE10 but so far nothing on the horizon for mobile or safari (http://caniuse.com/#feat=indexeddb). the size is still quite restrictive in chrome (5MB - https://developers.google.com/chrome/whitepapers/storage#temporary) but FF has a better story (http://support.mozilla.org/en-US/questions/818987).
i'd say that it's a novel idea to use Web Storage but in my opinion the real usefulness would be IndexedDB. as tom said, the store API is based around that same API.
On Oct 16, 2012, at 12:39 PM, Tom Trenka wrote:
> I don't want to rain on anyone's parade, but honestly if we're thinking of this as an offline thing it'd probably be much better to wrap the IndexedDB than LocalStorage, at least based on my experience (which admittedly is about 2 1/2 years old now and in the context of Adobe AIR). I remember running into the same problems Ken and Colin have alluded to; LocalStorage tends to be very slow, especially with larger data chunks...and IIRC there's a limit as to how much can be stored in it. And given that most people are using DTK to build single-page applications, that might end up being a bad thing.
> Kris deliberated designed the dojo/store API based on IndexedDB; perhaps if we're looking for an integrated solution, that would be a better path of investigation?
> On Tue, Oct 16, 2012 at 11:08 AM, Kenneth G. Franqueiro <kgf at dojotoolkit.org> wrote:
> Further responses inline.
> On 10/16/2012 11:52 AM, Kitson Kelly wrote:
> > Comments inline...
> > On 16 October 2012 16:10, Kenneth G. Franqueiro <kgf at dojotoolkit.org
> > <mailto:kgf at dojotoolkit.org>> wrote:
> > As with the last time the idea of web storage + dojo/store was brought
> > up, I would raise concern at the idea of introducing this "feature". I
> > may not have the most informed of opinions on the matter, but the
> > following things stick out to me:
> > * Which way would we "solve" this? One write per atomic store
> > operation, or have developers call a method to persist all items at
> > once? (Based on your idea of using Cache, I'm guesing the former; I'm
> > inclined to expect that the latter may actually perform better - i.e.
> > write all data to one key at once.)
> > The "why" to me is that we provide a Memory store with a consistent API
> > interface, but if you want to use Web Storage, you have to learn another
> > API. None of the widgets and other objects which are "data aware" can
> > leverage Web Storage, without some level of bespoke code. I personally
> > think this is making it difficult for creation of "offline" capable
> > applications with Dojo/Dijit both in the desktop and mobile space.
> It's not difficult to extend dojo/store/Memory with localStorage support
> if you want it. We do it (though perhaps not ideally, going back to the
> points in my previous reply) in one of the simple dgrid demos.
> > Of course an end developer could directly use the HTML5 Web Storage. I
> > maybe missing something, but if you needed to develop an application
> > that persisted date between page loads without always having a
> > connection to a server, outside of using cookies, how would you
> > accomplish this with Dojo?
> Let me pose an unrelated but equivalent question, in an attempt to
> illustrate a point: how would you iterate the keys of an object with
> Dojo? The answer is, you wouldn't. Dojo doesn't make a habit of
> providing solutions for problems that are already solved.
> > * But moreover, who's to say we really have the right to prescribe one
> > or the other for every situation, when in reality it would take someone
> > very few lines of code to implement either approach him/herself?
> > Again, how would you connect a Dijit, dgrid, GridX and any other
> > dojo/store API to Web Storage?
> You would write a few lines of code to extend dojo/store/Memory in
> whichever way you see fit to back it with localStorage. Again, I think
> it's disingenuous for us to make the decision as to "whichever way" for
> devs. It seems more like grounds for a tutorial (exploring multiple
> solutions) than a feature.
> > * Performance implications (see perhaps
> > http://www.nczonline.net/blog/2012/04/25/the-performance-of-localstorage-revisited/
> > and in particular, the first link in the footnotes)
> > A valid end-developer concern about which approach to take. I don't
> > think performance should preclude us from considering it though. Also,
> > as some of the comments have made, read into memory, work on data set,
> > save back to storage. Unless I am missing something though, I don't see
> > a way to easily persist data between sessions to create offline capable
> > applications any other way.
> I just don't want to see us implement something that encourages or makes
> it easy for people to shoot themselves in the foot. My point of linking
> that article wasn't so much about localStorage vs. something else, as it
> was cautioning against leaning heavily on it (and perhaps in the wrong way).
> > * Now you're also raising the implication of affecting another API
> > (dojo/store/Cache) just for the sake of a single implementation, which
> > to me sounds suspect (let alone that the potential implementation in
> > question also sounds suspect to begin with). I'm also not really sure I
> > understand what kind of changes you have in mind.
> > Possibly. That is why it is a proposal and the benefits of discussing
> > in the open. :-)
> > If we affect the Cache API in a way that break compatibility, then
> > obviously that is a non starter, but I would suspect people maybe
> > re-inventing the wheel, in that I have a level of concern with
> > dojo/store/Cache that it has no real logic of what data gets persisted
> > where other than "avoid fetching the same data again". It simply copies
> > all fetched data to both stores and if it doesn't think it has changed
> > retrieves it from the cached store. Whenever anything is .put() it
> > is immediately propagated to both stores. While Cache might not be the
> > right place to add it, there almost needs to be a mediation layer that
> > can be used to track transactions and commit those to a remote store in
> > a configurable fashion as well as synchronise between a local and remote
> > store in a configurable way. So I don't wholly see it as a
> > single implementation argument. I see it as a dojo/store compatible API
> > for Web Storage and providing an intelligent mechanism to
> > replicate/synchronise data between data stores.
> This sounds like it's sorely overcomplicating the scenario as opposed to
> what Cache currently solves. It sounds to me like it should be a
> separate entity, if it is to exist at all.
> > If it ends up being a "bad idea" there is plenty of time between now and
> > the release of 1.9 to agree to not do it, but if there is a "this might
> > work" then I am willing to expend time and effort on it.
> > Again, the main use case would be to allow the creation of offline
> > capable applications that will function between page re-loads or across
> > pages.
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