[aerogear-dev] Data Sync Thoughts

Summers Pittman supittma at redhat.com
Tue Jan 28 13:22:40 EST 2014 

On 01/28/2014 11:11 AM, Corinne Krych wrote:
> I think we still need the synchronisation mode in pull mode.
>
> How are we going to deal with this use case with simple push:
> UserA is offline update some data, then switch off his phone
> Some other users update data
> UserA open his app, he has missed some push notifications but still 
> want to sync his app.
That is the magic of Push systems.  He gets the messages when he comes 
online.

Device A and B and Server have data with a checksum of 42.
Device A goes offline.
Device A changes its data and has a checksum of 64.
Device B changes its data and has a checksum of 192.
Device B sends the expected server checksum of 42 and its new data to 
the server.
Server accepts B's Data, updates its checksum to 192, and sends a 
message to all Devices ( in this case just A)

Device B and Server go on a long date, but things don't work out and 
they end up splitting the check 50/50.  Device B is annoyed because she 
only got a salad but Server got the Surf and Turf.

Device A comes online and receives a message from the server.
Device A notices the server's checksum data is a change from 42 -> 192 
and not 42 -> 64.  Thus its copy is out of sync and fires a message to 
the User of Device A to resolve the data.
User A resolves the data and Device A sends the merged data to the server.
Device B gets a message of new data and updates to what the server has.

>
> ++
> Corinne
>
>
> On 28 January 2014 17:01, Summers Pittman <supittma at redhat.com 
> <mailto:supittma at redhat.com>> wrote:
>
>     On 01/28/2014 10:58 AM, Lucas Holmquist wrote:
>     > On Jan 28, 2014, at 10:54 AM, Summers Pittman
>     <supittma at redhat.com <mailto:supittma at redhat.com>> wrote:
>     >
>     >> On 01/28/2014 10:48 AM, Lucas Holmquist wrote:
>     >>> On Jan 28, 2014, at 10:30 AM, Summers Pittman
>     <supittma at redhat.com <mailto:supittma at redhat.com>> wrote:
>     >>>
>     >>>> On 01/28/2014 09:36 AM, Lucas Holmquist wrote:
>     >>>>> yup, this is another Data Sync thread,
>     >>>>>
>     >>>>>>  From a client side perspective, i have concerns that there
>     is still not a clear direction yet.
>     >>>>> I know there are multiple ideas floating around on what our
>     model should be,  i'm all for choice, but what about deciding on 1
>     model to get started with.  Then later once we have this nailed
>     down,  we can have other "adapters" with different models perhaps
>     >>>> All the data model is is an envelope of sync metadata around
>     an object
>     >>>> right?
>     >>> right
>     >>>
>     >>>> We also need to think about the API and server/client
>     protocol as well.
>     >>>>
>     >>>> I think that for sync 1.0 we could focus on the following
>     behavior (it
>     >>>> worked for my demos at least)
>     >>>>
>     >>>> 1.  We have a Sync factory similar to Pipeline, Authenticator,
>     >>>> Registrar, and KeyService.
>     >>>> 2.  The Sync factory consumes/manages Synchronizer instances.
>     >>>> 3.  AG Synchronizer listens for sync messages using
>     UnifiedPush endpoints.
>     >>> i thought for a 1.0 we weren't thinking about "realtime"
>     >> When I hear realtime I think sub 100 ms updates to all clients.
>     (think
>     >> gaming)
>     >>
>     >> What I thought we were going for was something closer to email.
>      The
>     >> data gets changed and at some point in the future the client
>     knows. More
>     >> specifically, the thing the ONE thing that makes sync special
>     is it is a
>     >> push instead of poll implementation.
>     > this makes sense,  but i guess it would be push when available.
>     thinking web and crappy web socket support( dang you carriers )
>     Right.  I'm not saying lets do something complicated.  I'm saying lets
>     use GCM, iOS CM, and simple push to send notifications to tell the
>     client something.  In simplePush case it is "this data changed,
>     get the
>     new stuff and update yourself".  In Android and iOS case it may be
>     that
>     or it may be "here is new data".
>
>     In general, I am fine for getting a message saying something like
>     Documents/Schedules/1/${revision}.  Then I can check my revisions,
>     fetch
>     data if necessary, update my local data, and send any updates.  That
>     SHOULD (I think) be doable with simplepush as well right?
>
>     >
>     >>>> 4.  AG Synchronizer sends sync messages using Pipes
>     >>>> 5.  AG Synchronizer holds local data in a store
>     >>>>
>     >>>> 6.  When AGSynchronizer gets a message it is responsible for
>     updating
>     >>>> the Store and then notifying code listing for updates OR for
>     notifying
>     >>>> the code that an error has occurred and needs to be addressed.
>     >>>>
>     >>>> 7.  When the developer updates data in the store, the
>     synchronizer
>     >>>> should package that data and send it to the server.  The
>     synchronizer is
>     >>>> responsible for error handling, retrying, back-off, etc.
>     >>>>
>     >>>> 8.  We should include multiple synchronizer implementations
>     to deal with
>     >>>> multiple very simple use cases which involve legacy systems. (For
>     >>>> instance polling to load static data on a schedule.)
>     >>>>
>     >>>> Thoughts? Tomatoes?
>     >>>>>
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