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Date: Fri, 19 Oct 2012 14:52:22 -0400
Message-ID: 
 <CAEeF2TfbecttNaG5RcGmnHxyBjywn4Gof2DgAJ6xeHfuZFOtFA@mail.gmail.com>
Subject: Re: IOS6 LocalStorage filesystem target location.
From: Michal Mocny <mmocny@chromium.org>
To: callback-dev@incubator.apache.org
Cc: Andrew Grieve <agrieve@chromium.org>, Shazron <shazron@gmail.com>,
	Shazron Abdullah <shaz@adobe.com>
Content-Type: text/plain; charset=ISO-8859-1

Brian, I think that is right, with the clarification to browser/ios is
webview/ios -- I am not certain if mobile Safari app localStorage
exhibits same behaviour.

Also, when they made that change in 5.1, it was pointed out that the
spec for localStorage actually says this is acceptable behaviour.
While I guess it is unlikely to come to desktop (storage isn't as
tight there), I could see that change potentially going to other
mobile platforms.

On Fri, Oct 19, 2012 at 2:26 PM, Brian LeRoux <b@brian.io> wrote:
> Ok. sorry I'm confused. Is this correct?
>
> browser/desktop: localStorage persists to the device
> browser/ios: localStorage might not persist to device
> cordova/ios: localStorage persists to the device
> cordova/android: localStorage persists to the device
>
>
> On Fri, Oct 19, 2012 at 11:20 AM, Andrew Grieve <agrieve@chromium.org> wrote:
>> Other platforms don't have the equivalent of iCloud, I don't think.
>> Native apps on iOS backup the contents of their non-Caches directory to
>> iCloud by default. I don't think being browser-based should change that.
>>
>>
>> On Fri, Oct 19, 2012 at 1:35 PM, Michal Mocny <mmocny@chromium.org> wrote:
>>>
>>> Its have already been different since the ios5.1 release.  We are just
>>> going to add a (non-default) option to opt out.
>>>
>>> We could change the default to be opt-out of backup, like the ios
>>> default, but that may be a breaking change.
>>>
>>> Also, while other platforms dont backup to cloud, they probably also
>>> persist locally, so the default behaviour of other cordova platforms
>>> already differs from the webview default on ios.
>>>
>>> What a mess!
>>>
>>> On Fri, Oct 19, 2012 at 1:28 PM, Brian LeRoux <b@brian.io> wrote:
>>> > Hey guys, I'm a little concerned that our default being different than
>>> > that of The Browser, and the other Cordova platforms. =/
>>> >
>>> > On Fri, Oct 19, 2012 at 8:01 AM, Michal Mocny <mmocny@chromium.org>
>>> > wrote:
>>> >> Also, I really hate using a magic number here.  Is there a canonical
>>> >> way to implement "enum" type in plist file?  A few google searches do
>>> >> not yield anything sane.
>>> >>
>>> >> Would it be more descriptive to use a string setting with values such
>>> >> as "none", "local", "cloud"?
>>> >>
>>> >> On Fri, Oct 19, 2012 at 10:35 AM, Michal Mocny <mmocny@chromium.org>
>>> >> wrote:
>>> >>> Yes, thats the conclusion I've made now, too.  I figure the app
>>> >>> developer can decide how he wants to take his changes with the review
>>> >>> process, and at least one user was very vocal to have this feature.
>>> >>>
>>> >>> Locally, I created a second setting instead of changing the format of
>>> >>> the current one, but I guess I'm fine with changing it in place as you
>>> >>> suggest, especially since I suspect no-one changed the default of the
>>> >>> current one (why would you?).
>>> >>>
>>> >>> There is one more potential combination that may be needed, but I am
>>> >>> not sure if it is worth the effort:  backup to iCloud on ios6 only.
>>> >>>
>>> >>> Potentially apple will reject backing up a copy of webstorage to
>>> >>> icloud on ios5.1, while at the same time we may still want to disable
>>> >>> CDVLocalStorage plugin on ios6, thus backing up to cloud on ios6 but
>>> >>> not 5.1.   Should I account for that, or leave it all-or-nothing and
>>> >>> punt for future releases if it becomes a problem?
>>> >>>
>>> >>> On Fri, Oct 19, 2012 at 10:10 AM, Andrew Grieve <agrieve@chromium.org>
>>> >>> wrote:
>>> >>>> I don't think we should read too much into the app rejection related
>>> >>>> to
>>> >>>> this. These things are often app-specific and not a result of a rule
>>> >>>> cordova itself doing something wrong.
>>> >>>>
>>> >>>> Proposal:
>>> >>>> We already have a setting for this in cordova.plist, as described
>>> >>>> here:
>>> >>>>
>>> >>>> https://github.com/apache/incubator-cordova-docs/blob/master/docs/en/edge/guide/project-settings/ios/index.md
>>> >>>>
>>> >>>> Right now, it's a BOOL, how about we change it to an int and have:
>>> >>>> 0 - Do not back up - Users should use this only when their
>>> >>>> DB/LocalStorage
>>> >>>> is a cache
>>> >>>> 1 - Backup to iCloud  (by setting the NSUserDefaults key)
>>> >>>> 2 - Backup to Device only  (and ensure to set the
>>> >>>> NSURLIsExcludedFromBackupKey)
>>> >>>>
>>> >>>> Option 2 would probably not be used much, but may be useful to have
>>> >>>> in case
>>> >>>> of app rejections.
>>> >>>> I think #1 should be the default. It's better to have things safe by
>>> >>>> default, and have apps get rejected than to have them get through the
>>> >>>> app-store and have their users hate them when data loss happens.
>>> >>>>
>>> >>>>
>>> >>>>
>>> >>>>
>>> >>>>
>>> >>>> On Thu, Oct 18, 2012 at 2:57 PM, Michal Mocny <mmocny@chromium.org>
>>> >>>> wrote:
>>> >>>>
>>> >>>>> Andrew: Yes, I was also thinking of advising to use FileSystem API
>>> >>>>> for
>>> >>>>> things they want to backup to iCloud.
>>> >>>>>
>>> >>>>> On Thu, Oct 18, 2012 at 1:55 PM, Shazron <shazron@gmail.com> wrote:
>>> >>>>> > To recap:
>>> >>>>> >
>>> >>>>> > iOS 6 indeed does solve this problem with the NSUserDefaults key
>>> >>>>> > "WebKitStoreWebDataForBackup" - which I think the web data is
>>> >>>>> > stored
>>> >>>>> > in Library/Caches as changed by iOS 5.1.
>>> >>>>>
>>> >>>>> What do you mean by "ios6 does solve this problem"?
>>> >>>>>
>>> >>>>> The WebKitStoreWebDataForBackup flag changes the LocalStorage
>>> >>>>> location
>>> >>>>> from /Library/Caches to /Library/WebKit/LocalStorage (ie, back to
>>> >>>>> where it was before ios5.1 moved it to Cache folder).  Setting this
>>> >>>>> flag means LocalStorage persists (great) but also backs up to iCloud
>>> >>>>> (may not be desired -- and arguably should never be desired).
>>> >>>>>
>>> >>>>> >
>>> >>>>> > iOS 5.1 it is stored in Library/Caches thus it is not backed up -
>>> >>>>> > that's why we backed it up to the Documents/Backups folder (and
>>> >>>>> > backed
>>> >>>>> > up/restore to /Library/Caches). We do _not_ set the
>>> >>>>> > NSURLIsExcludedFromBackupKey on the Documents/Backups folder, if
>>> >>>>> > the
>>> >>>>> > dev wanted to, they can do so using the File API's
>>> >>>>> > FileEntry.setMetadata function.
>>> >>>>>
>>> >>>>> Correct -- and I did not know that we can use FileEntry.setMetadata
>>> >>>>> for this.  I'll look into it, thanks!
>>> >>>>>
>>> >>>>> >
>>> >>>>> > CB-1561 (Apple rejection) could be solved by them setting the
>>> >>>>> > metadata
>>> >>>>> > bit. But if they want it to be backed up by iCloud they shouldn't
>>> >>>>> > do
>>> >>>>> > set that bit - but then if they _don't_ set that bit -- rejection.
>>> >>>>>
>>> >>>>> If not setting that bit causes rejection, then seems we should just
>>> >>>>> set it by default.  Somehow apps have managed to sneak by the review
>>> >>>>> process until now (perhaps the changes to ios6 have changed the
>>> >>>>> review
>>> >>>>> process?).
>>> >>>>>
>>> >>>>> >
>>> >>>>> > Upgrading from iOS 5.1 to 6 shouldn't be a problem since
>>> >>>>> > ultimately
>>> >>>>> > the database locations are still in Library/Caches -- we just need
>>> >>>>> > to
>>> >>>>> > set the NSUserDefaults key.
>>> >>>>>
>>> >>>>> If we set the NSUserDefaults key, the database location does change.
>>> >>>>> Possibly this migration is provided by default (otherwise all
>>> >>>>> webview
>>> >>>>> apps would lose old data with manual restore), but we still need to
>>> >>>>> restore our custom ios5.1 backup for first-launch-after-upgrade
>>> >>>>> case.
>>> >>>>> This has been implemented already in 2.1, though there were some
>>> >>>>> issues+bugfixes.
>>> >>>>>
>>> >>>>> >
>>> >>>>> > This is solved by iOS 6, but we don't have a clear answer for iOS
>>> >>>>> > 5.1
>>> >>>>> > (besides upgrading to iOS 6) -- our original fix is not tenable
>>> >>>>> > anymore (
>>> >>>>>
>>> >>>>> http://phonegap.com/2012/04/18/ios-5-1-and-the-embedded-uiwebview-with-cordova/
>>> >>>>> )
>>> >>>>>
>>> >>>>> While I don't yet see the point of backing up LocalStorage to the
>>> >>>>> cloud, I will concede that it may be a lesser evil compared to
>>> >>>>> forever
>>> >>>>> using the LocalStorage Plugin/hack, which is necessary for ios5.1.
>>> >>>>>
>>> >>>>> For additional context: we already used the UserDefault setting for
>>> >>>>> 2.1 release, yet I've reverted back to using the Plugin in current
>>> >>>>> git
>>> >>>>> version, since I thought iCloud backup was a mistake.
>>> >>>>>
>>> >>>>> >
>>> >>>>> >
>>> >>>>> >
>>> >>>>> >
>>> >>>>>
>>> >>>>> Summarizing:
>>> >>>>> - I think we should flag any backups we make with
>>> >>>>> NSURLIsExcludedFromBackupKey *by default* (ios5.1 must do this, ios6
>>> >>>>> depends on decision to use NSUserDefaults).
>>> >>>>> - ios6 we have a choice (to cloud or not to cloud).  Possibly the
>>> >>>>> choice should be up to the app developer.  I now again think we
>>> >>>>> should
>>> >>>>> backup to iCloud, if only to not need use our plugin, and to not
>>> >>>>> change behavior from 2.1 (again).
>>> >>>>>
>>> >>>>> Additionally:
>>> >>>>> - The current location of our local backups (Documents folder) is
>>> >>>>> incorrect.  Apple hasn't rejected any apps for this, but it should
>>> >>>>> be
>>> >>>>> in /Library/Application Support (fixed).
>>> >>>>> - I've tested restoring localstorage with various upgrade paths, but
>>> >>>>> I
>>> >>>>> may have just uncovered a bug with restoring websql.
>>> >>>>> - We should probably document some of this for the 2.2 release.
>>> >>>>>
>>> >>>>> >
>>> >>>>> > On Thu, Oct 18, 2012 at 8:06 AM, Michal Mocny
>>> >>>>> > <mmocny@chromium.org>
>>> >>>>> wrote:
>>> >>>>> >> So there has been a lot of back and forth recently about where
>>> >>>>> >> and how
>>> >>>>> >> to backup localstorage (see:
>>> >>>>> >> https://issues.apache.org/jira/browse/CB-1561)
>>> >>>>> >>
>>> >>>>> >> At least one users wants these to backup to iCloud -- and while I
>>> >>>>> >> don't see how that makes real sense, the fact that apple added a
>>> >>>>> >> flag
>>> >>>>> >> to allow this in ios6 maybe signals we should allow the option.
>>> >>>>> >>
>>> >>>>> >> Given that this cannot work on versions less than 5.1, may not be
>>> >>>>> >> enabled on ios6, and may not work the way developers expect
>>> >>>>> >> anyway, is
>>> >>>>> >> there a point?
>>> >>>>> >>
>>> >>>>> >> Shaz, would appreciate your opinion here, if you are around.
>>> >>>>> >>
>>> >>>>> >> -Michal
>>> >>>>> >>
>>> >>>>> >> On Fri, Oct 5, 2012 at 2:23 PM, Michal Mocny
>>> >>>>> >> <mmocny@chromium.org>
>>> >>>>> wrote:
>>> >>>>> >>> Done.
>>> >>>>> >>>
>>> >>>>> >>>
>>> >>>>>
>>> >>>>> https://git-wip-us.apache.org/repos/asf?p=incubator-cordova-ios.git;a=commit;h=6e170879aa37d33701739fc3c28ed9f78156bf1f
>>> >>>>> >>>
>>> >>>>> >>> As of today we backup to a different location so as not to upset
>>> >>>>> >>> the
>>> >>>>> apple
>>> >>>>> >>> app review overlords, and we do not backup to icloud on ios6 any
>>> >>>>> >>> more.
>>> >>>>> >>>
>>> >>>>> >>> I've added support for loading all the various old database
>>> >>>>> >>> locations
>>> >>>>> the
>>> >>>>> >>> first time you run an upgraded app, but if there are only issues
>>> >>>>> reported
>>> >>>>> >>> about this, send them my way!
>>> >>>>> >>>
>>> >>>>> >>> -Michal
>>> >>>>> >>>
>>> >>>>> >>>
>>> >>>>> >>> On Wed, Oct 3, 2012 at 4:43 PM, Dave Johnson
>>> >>>>> >>> <dave.c.johnson@gmail.com
>>> >>>>> >
>>> >>>>> >>> wrote:
>>> >>>>> >>>>
>>> >>>>> >>>> I agree backing up to iCloud seems like a bad idea. Let alone
>>> >>>>> >>>> the
>>> >>>>> >>>> Apple policy issues.
>>> >>>>> >>>>
>>> >>>>> >>>> -d
>>> >>>>> >>>>
>>> >>>>> >>>> On Wed, Oct 3, 2012 at 10:31 PM, Michal Mocny
>>> >>>>> >>>> <mmocny@google.com>
>>> >>>>> wrote:
>>> >>>>> >>>> > === Background ===
>>> >>>>> >>>> >
>>> >>>>> >>>> > In IOS5.1 moved these files from the "documents" folder to a
>>> >>>>> >>>> > "cache"
>>> >>>>> >>>> > folder, which meant they may get purged when the system
>>> >>>>> >>>> > decided
>>> >>>>> memory
>>> >>>>> >>>> > was
>>> >>>>> >>>> > geting tight.  To get around this, we implemented a manual
>>> >>>>> >>>> > backup/restore
>>> >>>>> >>>> > plugin (CDVLocalStorage).  (I was not here for this work,
>>> >>>>> >>>> > piecing
>>> >>>>> >>>> > history
>>> >>>>> >>>> > together.)
>>> >>>>> >>>> >
>>> >>>>> >>>> > With IOS6, Apply added a new UserDefaults option
>>> >>>>> >>>> > (WebKitStoreWebDataForBackup) to backup these files onto
>>> >>>>> >>>> > iCloud,
>>> >>>>> with
>>> >>>>> >>>> > the
>>> >>>>> >>>> > side effect of having persistant local storage without the
>>> >>>>> >>>> > need for
>>> >>>>> our
>>> >>>>> >>>> > backup hacks/plugin.
>>> >>>>> >>>> >
>>> >>>>> >>>> > ========
>>> >>>>> >>>> >
>>> >>>>> >>>> > Initially I used this new IOS6 feature as a means to get
>>> >>>>> >>>> > persistant
>>> >>>>> >>>> > localstorage (there was a bug to add that when I started
>>> >>>>> contributing).
>>> >>>>> >>>> >
>>> >>>>> >>>> > However, its actually been against apple policy to store
>>> >>>>> >>>> > these
>>> >>>>> files in
>>> >>>>> >>>> > the
>>> >>>>> >>>> > documents folder, and user apps are being rejected from app
>>> >>>>> >>>> > store,
>>> >>>>> see:
>>> >>>>> >>>> > https://issues.apache.org/jira/browse/CB-1561.
>>> >>>>> >>>> >
>>> >>>>> >>>> > More importantly, I don't think we should want to backup
>>> >>>>> >>>> > these
>>> >>>>> files to
>>> >>>>> >>>> > a
>>> >>>>> >>>> > users' iCloud just to get persistant storage.
>>> >>>>> >>>> >
>>> >>>>> >>>> > I think we should re-enable the plugin used for ios5.1 on
>>> >>>>> >>>> > ios6 and
>>> >>>>> not
>>> >>>>> >>>> > backup to iCloud.  This may have perf implications but no
>>> >>>>> >>>> > more-so
>>> >>>>> than
>>> >>>>> >>>> > we
>>> >>>>> >>>> > have already been dealing with until now (and which I haven't
>>> >>>>> >>>> > benchmarked).
>>> >>>>> >>>> >
>>> >>>>> >>>> > What do others think?  There are other means to fix the
>>> >>>>> >>>> > current
>>> >>>>> issues
>>> >>>>> >>>> > and
>>> >>>>> >>>> > continue to use the next setting, so we do have options here.
>>> >>>>> >>>
>>> >>>>> >>>
>>> >>>>>
>>
>>