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[whatwg] Structured clone algorithm on LocalStorage

From: Jeremy Orlow <jorlow@chromium.org>
Date: Wed, 23 Sep 2009 15:29:38 -0700
Message-ID: <5dd9e5c50909231529i3c114b4dkf45c63096fc7e536@mail.gmail.com>
On Wed, Sep 23, 2009 at 3:15 PM, Jonas Sicking <jonas at sicking.cc> wrote:

> On Wed, Sep 23, 2009 at 2:53 PM, Brett Cannon <brett at python.org> wrote:
> > On Wed, Sep 23, 2009 at 13:35, Jeremy Orlow <jorlow at chromium.org> wrote:
> >> What are the use cases for wanting to store data beyond strings (and
> what
> >> can be serialized into strings) in LocalStorage?  I can't think of any
> that
> >> outweigh the negatives:
> >> 1)  From previous threads, I think it's fair to say that we can all
> agreed
> >> that LocalStorage is a regrettable API (mainly due to its synchronous
> >> nature).  If so, it seems that making it more powerful and thus more
> >> attractive to developers is just asking for trouble.  After all, the
> more
> >> people use it, the more lock contention there'll be, and the more
> browser UI
> >> jank users will be sure to experience.  This will also be worse because
> >> it'll be easier for developers to store large objects in LoaclStorage.
> >> 2)  As far as I can tell, there's no where else in the spec where you
> have
> >> to serialize structured clone(able) data to disk.  Given that
> LocalStorage
> >> is supposed to throw an exception if any ImageData is contained and
> since
> >> File and FileData objects are legal, it seems as though making
> LocalStorage
> >> handle structured clone data has a fairly high cost to implementors.
>  Not to
> >> mention that disallowing ImageData in only this one case is not
> intuitive.
> >> I think allowing structured clone(able) data in LocalStorage is a big
> >> mistake.  Enough so that, if SessionStorage and LocalStorage can't
> diverge
> >> on this issue, it'd be worth taking the power away from SessionStorage.
> >> J
> >
> > Speaking from experience, I have been using localStorage in my PhD
> > thesis work w/o any real need for structured clones (I would have used
> > Web Database but it isn't widely used yet and I was not sure if it was
> > going to make the cut in the end). All it took to come close to
> > simulating structured clones now was to develop my own compatibility
> > wrapper for localStorage (http://realstorage.googlecode.com for those
> > who care) and add setJSONObject() and getJSONObject() methods on the
> > wrapper. Works w/o issue.
>
> Actually, this seems like a prime reason *to* add structured storage
> support. Obviously string data wasn't enough for you so you had to
> write extra code in order to work around that. If structured clones
> had been natively supported you both would have had to write less
> code, and the resulting algorithms would have been faster. Faster
> since the browser can serialize/parser to/from a binary internal
> format faster than to/from JSON through the JSON serializer/parser.


Yes, but since LocalStorage is already widely deployed, authors are stuck
with the the structured clone-less version of LocalStorage for a very long
time.  So the only way an app can store anything that can't be JSONified is
to break backwards compatibility.




On Wed, Sep 23, 2009 at 3:11 PM, Jonas Sicking <jonas at sicking.cc> wrote:

> On Wed, Sep 23, 2009 at 1:35 PM, Jeremy Orlow <jorlow at chromium.org> wrote:
> > What are the use cases for wanting to store data beyond strings (and what
> > can be serialized into strings) in LocalStorage?  I can't think of any
> that
> > outweigh the negatives:
> > 1)  From previous threads, I think it's fair to say that we can all
> agreed
> > that LocalStorage is a regrettable API (mainly due to its synchronous
> > nature).  If so, it seems that making it more powerful and thus more
> > attractive to developers is just asking for trouble.  After all, the more
> > people use it, the more lock contention there'll be, and the more browser
> UI
> > jank users will be sure to experience.  This will also be worse because
> > it'll be easier for developers to store large objects in LoaclStorage.
> > 2)  As far as I can tell, there's no where else in the spec where you
> have
> > to serialize structured clone(able) data to disk.  Given that
> LocalStorage
> > is supposed to throw an exception if any ImageData is contained and since
> > File and FileData objects are legal, it seems as though making
> LocalStorage
> > handle structured clone data has a fairly high cost to implementors.  Not
> to
> > mention that disallowing ImageData in only this one case is not
> intuitive.
> > I think allowing structured clone(able) data in LocalStorage is a big
> > mistake.  Enough so that, if SessionStorage and LocalStorage can't
> diverge
> > on this issue, it'd be worth taking the power away from SessionStorage.
>
> Despite localStorage unfortunate locking contention problem, it's
> become quite a popular API. It's also very successful in terms of
> browser deployment since it's available in at least latest versions of
> IE, Safari, Firefox, and Chrome. Don't know about support in Opera?
>

The more popular it becomes, the more it's going to hurt UA developers, web
developers, and users.  I don't see why this is an argument for making it
more powerful.

In addition, this argument assumes that Microsoft (and other UAs) will
implement the structured clone version of LocalStorage.  Has anyone (or can
anyone) from Microsoft comment on this?

This is not a small feature to add.  Yes, it's smaller than creating a new
storage mechanism (that everyone is willing to adopt), but I still think
that's what we should be looking at.  Rather than polishing a turd.
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