Synchronization Architecture for

Cloud powered Mobile Apps

Prithiviraj Damodaranwww.ByteContinnum.com

From the App User and Device Resource view point the following are some of the critical factors a cloud backed mobile engineering team should consider.

• Smart Disk space usage - A lot of apps including some

popular social media apps abuse device disk space. Every time the

apps sync with the cloud counter part they bring down fresh data.

Apps should be considerate of device user and should come up with

some clean-up mechanism.

Major Concerns Addressed 1 of 2

• Smart Network usage – Be it upstream or downstream sync

i.e. apps as well as the cloud counter parts should be designed to be

very frugal about the number of bytes sent over the wire as well as

the number of network calls as it directly impacts the data usage and

hence the device user.

• Smart Battery consumption - For instance

• Apps which broadcast real time user activities should smartly club

syncs to reduce multiple device pings

• Location and geo fence based apps should use the right strategy to

avoid draining device battery.

Major Concerns Addressed 2 of 2

Cloud-2-Device• On-AppStartup• On-AppBackground2Foreground Transition• On-AppSignin (if any)• On-Demand user action

Device-2-Cloud• On-AppUITransition

Event Driven Synchronization

Cloud-2-Device

On-Start-up - online

• First time fetch of current Location•  Instantiate N/W Connection receiver. (Wifi/Data)

•  “All” data if new device or “Newer” datadeals since last sync date, if used device.

•  Clean up older disk cache records. (Cache date <Current date and un synchronized)•  Any other Metadata sync or change in Business rules or disclaimers etc..

On-Start-up - offline

• If new device change to offline mode and provide an option to retry N/W connection•  Active fetch of current Location.•  If used device use last synced data•  Clean up older disk cache records. (Cache date < Current date and synched)

On-Sign in

•  User data later than last sync if already used device - Something like getting the newer emails from the server since last sync. Using the app in Multiple devices doesn’t affect this part of the sync. But it does affects the synch of user specific settings/ preferences.•  User specific notifications – offers or expiry notices etc.

Since there could be multiple devices in which user could login from, every device will have to maintain last sign in timestamp and Cloud will maintain last synchronization timestamp at levels desired. Every time during sign-in If these 2 time stamps vary then it calls for Synching all user specific settings data

•  User specific app settings and preferences

On-Sign in - offline

•  show the message and continue as guest in offline mode.

On-Demand Sync – 2 Way•  All data listing screens shall support on-Demand sync. Using a pull down or swipe down gesture user can initiate sync.

•  During swipe down n/w state will be first checked before making the Sync call. If offline appropriate message shall be shown.

Best real life example would be your Gmail app. Try to “star” an email and Swipe down. Your “star” should reflect in your server (try and open gmail in another device or PC) and if you had new emails that would be in your device too.So 2 way cloud sync.

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Rest APIs

On-Demand Sync – 2 Way

Device-2-Cloud

•  All user activities shall be stored at disk first and synced on the

next UI based action like a UI Transition. The approach is

disk first and asynchronous calls to cloud. The stored data shall look

something like below. Choice of storage could be disk caches like

SQLLite or something similar.

Data Cache Date Sync Status

{“test”:”data”} 2014-08-01:00:00:00 Sync Progress

{“test”:”data”} 2014-08-01:00:00:00 Sync Complete

{“test”:”data”} 2014-08-01:00:00:00 To be Synced

On-UITransition

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As a part of the strategy make sure all deal breaking features (whichever possible) are supported in offline mode for the success of the app. This might require some careful planning and some extra processing / storing required data in the device.

Offline mode