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Re: FileAPI use case: making an image downloading app

From: Eric Uhrhane <ericu@google.com>
Date: Mon, 10 Jan 2011 15:14:49 -0800
Message-ID: <AANLkTikpqgfYgzvo1T03xmSZrHuhMh09FVKiwTX2diPo@mail.gmail.com>
To: "Gregg Tavares (wrk)" <gman@google.com>
Cc: Charles Pritchard <chuck@jumis.com>, Web Applications Working Group WG <public-webapps@w3.org>
On Fri, Dec 17, 2010 at 5:03 PM, Gregg Tavares (wrk) <gman@google.com> wrote:
>
>
> On Fri, Dec 17, 2010 at 4:16 PM, Charles Pritchard <chuck@jumis.com> wrote:
>>
>> We're actively developing such functionality.
>>
>> The limit per directory is for the sake of the os file system. If you want
>> to create a data store, use indexedDB or use standard file system practices
>> (create a subdirectory tree).
>
> I think you're missing the point. If I have a folder with 6000 files on some
> server and I want to mirror that through the FileAPI to the user's local
> machine I'm screwed. I can't **mirror** it if it's not a mirror.
>
>>
>> Disk space availability (quota) is an issue no matter what happens. When
>> downloading 1000 images, you'll still only be doing so x at a time.
>
> I don't see the point you're trying to make here. I don't know the size of
> the images before hand. Many internet APIs make getting the sizes
> prohibitively expensive. One REST call per file. So before I can download a
> single file I'd have to issue 1000 REST XHRs to find the sizes of the files
> (waiting the several minutes for that to complete) before I can ask the user
> for the space needed.  That's not a good user experience. If on the other
> hand the user can give me permission for unlimited space then I can just
> start downloading the files without having to find out their ultimate size.
> I suppose I can just request 1 terabyte up front. Or query how much space is
> free and ask for all of it.

I think that in this particular case, you'd want a better server API.
"Hey, I want to download this whole directory.  How much space will I
need?".  I realize that that's not always an option, but it's an
alternative to what I just posted elsewhere in this thread: let the UA
come up with a better quota system+UI.

>> This issues are inherent in the design of any application of scale. At
>> this point, the file system API does work for the use case you're
>> describing.
>>
>> It'd be nice to see Blob storage better integrated with Web Storage Apis.
>> Ian has already spoken to this, but no followers yet (afaik).
>>
>> -Charles
>>
>>
>>
>> On Dec 17, 2010, at 3:34 PM, "Gregg Tavares (wrk)" <gman@google.com>
>> wrote:
>>
>> > Sorry if this has been covered before.
>> >
>> > I've been wanting to write an app to download images from photo sites
>> > and I'm wondering if this use case has been considered for the FileAPI wrt
>> > Directories and System.
>> >
>> > If I understand the current spec it seems like their are some possible
>> > issues.
>> >
>> > #1) The spec says there is a 5000 file limit or directory.
>> >
>> > #2) The spec requires an app to specify how much storage it needs
>> >
>> > I understand the desire for the limits.  What about an app being able to
>> > request unlimited storage and unlimited files? The UA can decide how to
>> > present something to the user to grant permission if they want.
>> >
>> > Arguments against leaving it as is:
>> >
>> > The 5000 file limit seems arbitrary. Any app that hits that limit will
>> > probably require serious re-engineering to work around it. It will not only
>> > have to some how describe a mapping between files on a server that may not
>> > have that limit, it also has the issue the user might have something
>> > organized that way and will require the user to re-organize. I realize that
>> > 5000 is a large number. I'm sure the author of csh though 1700 entires in a
>> > glob was a reasonable limit as well. We all know how well that turned out
>> > :-(   It's easy to imagine a video editing app that edits and composites
>> > still images. If there are a few layers and 1 image per layer it could
>> > easily add up to more than 5000 files in a single folder.
>> >
>> > The size limit also has issues. For many apps the size limit will be no
>> > problem but for others....  Example: You make ray tracing program, it traces
>> > each frame and saves the files to disc. When it runs out of room, what is
>> > its options? (1) fail. (2) request a file system of a larger size. The
>> > problem is (2) will require user input. Imagine you start your render before
>> > you leave work expecting it to finish by the time you get in only to find
>> > that 2 hours after you left the UA popped up a confirmation "this app
>> > requests more space"
>> >
>> > The same would be true for an image downloading app. You start the app
>> > to download a 1000 images, not knowing their sizes before hand. You start it
>> > and leave. Half way through the UA puts up a conformation asking for more
>> > space.
>> >
>> > Have these use cases already come up and been rejected?
>> >
>> >
>> >
>
>
Received on Monday, 10 January 2011 23:15:34 GMT

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