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Re: [IndexedDB] Granting storage quotas

From: Michael Nordman <michaeln@google.com>
Date: Tue, 20 Apr 2010 15:31:02 -0700
Message-ID: <p2tfa2eab051004201531k8f63cffbk5d1095723435b835@mail.gmail.com>
To: Nikunj Mehta <nikunj@o-micron.com>
Cc: public-webapps@w3.org, Joćo Eiras <joaoe@opera.com>, Mark Seaborn <mseaborn@chromium.org>
On Tue, Apr 20, 2010 at 3:10 PM, Nikunj Mehta <nikunj@o-micron.com> wrote:

> As I see it, there's no such thing as "permanent" storage for Web browser
> managed data. Even if a site expresses preferences that it would like to
> keep its data resident for a long time, there cannot be a "guarantee" for
> the data to be there permanently. If applications are bound to have to deal
> with data disappearing while they are not running, we should not need to
> spec browser behavior around the notion of purgeable or permanent.

I see a difference between a cached version of a picture you've downloaded
vs a new picture taken while on vacation by a camera built into the device
and placed into a local repository managed by the user-agent. There is only
one copy of that picture in the world.

I'm looking for ways to make these storage APIs widely available w/o a lot
of user-prompting, but also for ways for webapps to express stronger
guarantees when needed. I think the notion of purgeable vs permanent may
help reconcile these conflicting goals.

> It makes sense for an application, OTOH, to say that it does not need data
> to be stored on disk. IOW, create a database that is non-durable and, hence,
> kept only in memory. Such databases are required to be empty upon creation.
> They may be spilled over to disk, if implementations like to, but they will
> not be retained from session to session.
> Nikunj
> On Apr 20, 2010, at 2:37 PM, Michael Nordman wrote:
> I'd like to back up and challenge the notion of a per-site quota.
> In this discussion and others there is an underlying assumption that each
> site has some well defined limit that the user-agent has granted it. I doubt
> that's the best model. (Fyi: the chrome team's overly simplistic model
> whereby each site gets 5M was not chosen because its a good model, this was
> done just to proceed with building out the storage APIs independent of a
> real storage management strategy).
> I'd like to set aside the per-site quota assumption and explore some
> alternative models for web storage management.
> Some thoughts about the world we're designing for. There are an open ended
> number of sites, each of which *could* use web storage in some form. From
> that fact alone, it's impossible to come up with a quota that could be
> granted to each and every site. It seems likely that the number of sites
> that will actually require "permanent" storage is small compared to the
> number of sites that *could* make use of more "volatile" storage, to borrow
> jorlow's term, where the volatile data on disk can get scrapped by the
> user-agent as needed. Maybe a better term for that class of storage is
> "purgeable"?
> Maybe we should be designing for what seems to be the more common case,
> lots of sites that make use of volatile/purgeable storage. But also come up
> a means whereby the smaller number of sites that require stronger guarantees
> can express the need for more permanent storage.
> "What if" by default all local storage is "purgeable". A lot of quota
> issues melt away in this case since the user agent is free to reclaim
> anything at anytime. I think it'd be reasonable if the user-agent never
> asked the user anything on a per-site basis. A user-agent could warn when
> system disk space crossed thresholds and give the user an option to set
> limits  on system disk space usage for webstorage as a whole.
> "What if" when creating local storage repositories (WebDBs or IndexedDBs or
> WebFileSystems or AppCaches) there was an optional means for the webapp to
> express "please consider this a permanent storage repository". The first
> time a site request "permanent" storage could be a reasonable time to
> interact with the user in some form, or to consult the user prefs about
> allowing permanent storage w/o being asked.
> I think ericu is baking in a distinction in between 'permanent' and
> 'temporary' in the FileSystem API he's working on. Some harmony across all
> flavors of local storage could be good.
> I actually think local storage management is an area where the webplatform
> has a chance to do a much better job then the desktop platforms have
> historically done. We don't need no stinking quotas ;) But we also don't
> need untold amounts of unused permanent storage littering disk drives
> needlessly around the globe (until the user gets a new system). A silly
> analogy. A computer is like a ship at sea. After years of usage, a whole
> bunch of barnacles build up on the hull and slow the vessel down. The
> webplatform to date is barnacle free in this area because there are no
> permanent local storage facilities... lets try to make these new features
> not so barnacle prone too.
> Cheers
> -Michael
> On Tue, Apr 20, 2010 at 11:17 AM, Shawn Wilsher <sdwilsh@mozilla.com>wrote:
>> On 4/20/2010 4:11 AM, Mark Seaborn wrote:
>>> 1) It doesn't allow a web app to ask for a storage allocation up front,
>>> before it starts to consume the storage.
>> Why does that matter?
>>  2) In Opera, the quota can only be increased in multiples of about 15, so
>>> it
>>> takes three prompts to get up into the range of gigabytes.
>> But there is an unlimited option, yeah?
>>  3) The web app can't choose when the question is put to the user.
>>> 4) The web app doesn't know how much storage has been allocated, so it
>>> doesn't know when a question will be asked.
>>> 5) In Opera, if the user chooses "Reject", they don't get prompted again.
>>> This means that asking the user at an appropriate time is important for
>>> the
>>> continued functioning of the web app.  Prompting the user at the wrong
>>> time
>>> will interrupt them with a page-modal dialog which they might want to get
>>> rid of with "Reject", which would potentially break the web app by
>>> leaving
>>> it unable to get more storage.
>> These all feel like user-agent specific worries on how the user agent
>> wants to bring this to the attention of the user.
>> Cheers,
>> Shawn
Received on Tuesday, 20 April 2010 22:31:34 UTC

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