[whatwg] Storage quota introspection and modification

[Ian Fette (イアンフェッティ)]

As I talk with more application developers (both within Google and at
large), one thing that consistently gets pointed out to me as a problem is
the notion of the opaqueness of storage quotas in all of the new storage
mechanisms (Local Storage, Web SQL Database, Web Indexed Database, the
Filesystem API being worked on in DAP, etc). First, without being able to
know how large your quota currently is and how much headroom you are using,
it is very difficult to plan in an efficient manner. For instance, if you
are trying to sync email, I think it is reasonable to ask "how much space do
I have," as opposed to just getting halfway through an update and finding
out that you hit your quota, rolling back the transaction, trying again with
a smaller subset, realizing you still hit your quota, etc.

I would like to see a method added, for any "storage mechanism", something
like "GetCurrentQuota()" and "GetCurrentQuotaUsed()". (I specifically don't
care what they're called or the details, e.g. whether they need to be
callbacks, I just want to see us address this use case.)

Secondly, I think we need a better answer for obtaining a larger quota.
Let's think for a moment about the use cases -- in most instances, I am
going to make a decision that I want to use an application offline. (I
personally would not expect to browse to a site and then just happen to be
able to use it offline, nor do I expect users to have that expectation or
experience. Rather, I expect going through some sort of flow like clicking
something that says "Yes, I want to use Application X offline". At this
point, I want to get any permissioning issues out of the way. I don't want
to wait until the data sync to the Web XXX Database starts failing 10
minutes later to pop up an infobar that is no longer in the user's current
flow / state of mind, I don't want to then pop up another infobar 30 minutes
later saying their Filesystem quota is full, etc. I want to be able to get
this out of the way all at once, at a point in time where I believe the user
is actually in the mindset / task of deciding that they want to use my web
application. I specifically do not want to have to deal with 4 different
infobars, potentially at 4 different points in time, to use an application I
have decided I want to use.

To that point, I would like to see a method added (presumably that can only
be called in response to a user action) that would allow my page to request
a bundle of permissions. I am going to go out on a limb here and include
geolocation in this bundle. Some sort of a callback type API where I pass in
a list of permissions that I want, the UA is free to display this to the
user in whatever mechanism it determines appropriate (if at all -- e.g. if
the user has already denied geolocation and that's being requested again, as
a UA i might decide not to present that request). That is, I could pass in
something like ["LocalStorageQuota", 20*1024*1024 /* 20M */, "WebSQLQuota",
1*1024*1024*1024 /* 1GB */, "FileSystemQuota", 10*1024*1024*1024 /* 10GB */,
"Geolocation", true], and the callback could then (as a convenience)
indicate the current quota for all of the things that I asked for, so that I
could figure out whether the user accepted, denied, or accepted and modified
the request and how I can then proceed (or not proceed). Again, I don't care
terribly about the details of how the API looks, the above is just meant for
illustration.

-Ian
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