CODEWITHSUNDEEP
androidiosmobilesynchronization
thealeksandr
thealeksandr

Reputation: 1736

Sync data between client and server

I have mobile app. Something like to do list or calendar. Teoretically user can have a few devices with that application on a defferent platforms and so on. I would like to create a automatic synchronization between them through a own server. What is the best practice: update all the information or only the changes? On the one hand usually there is no a lot of data when it's about a to do list but who knows?

Upvotes: 1

Views: 2880

Answers (5)

Niren Kochhar
Niren Kochhar

Reputation: 1

Here is another approach.

Issue :I need to have the appointments of doctors syned to client (mobile device) from the server. Now the appointments can drop off or the data could possibly change on the server. Having the client to know what change and sending a request back to server could be an expensive service.

Possible approach : Have the server do the heavy lifting. Keep a table which stores values of time stamp and if a change happened with regard to an appointment - cancellation / reschedule etc. The client would then look at this table to see if anything changed. In reality we don't need to sync anything but only the delta which server can provide to the client based on what it has and what is at Client. There is one aspect which needs to be taken care of is updation of info from client to server and traditional conflict management can be done where client can update the server when a data connectivity between client and server exists.

Essentially the approach is to have only the deltas synced by maintaining a checksum or data change log to PUSH changes to the client.

Upvotes: 0

orandolabs
orandolabs

Reputation: 11

There is a new alternative to the syncing problem. It's called EnduroSync from Orando Labs. You can sync object data stores between devices on Android and iOS now, with others coming soon.

Full Disclosure: I work for Orando Labs.

The EnduroSync clients allow you to create object data stores on the local devices. The clients are fairly sophisticated - data is modeled as native objects for each client we support (iOS and Android now, more coming). The clients work offline and online. The data is saved to an sqlite database locally.

As you change objects in your model, the deltas are recorded on the device. At some point, you can 'sync' the object data store. Syncing uses a commit/push/pull process (like git), but this is invisible to you. The sync brings your local copy up to date with whatever is on the server, and sends up any changes you have made. Conflicts are resolved using a timestamp based merge, so newer data is not overwritten by older data.

EnduroSync is an online service, so there is no server setup on your end.

There is also a flexible permission system which lets you share the object data stores in a variety of ways. For instance, most applications will have one or more object data stores for each user, for preferences, notes, tags, etc. You can also share object data stores per app, per user type, and with wild cards, many other ways.

So basically you use our client SDK's to model your data on the device. Modeling is with simple objects in the native programming language of the device. If you sign up for the syncing service, you get the syncing also.

Upvotes: 0

Eugene Mayevski 'Callback
Eugene Mayevski 'Callback

Reputation: 46040

The correct approach is not date/time as others suggest, as time can go out of sync. The right algorithm is to keep the checksum of the data entries during last synchronization. On next synchronization you compare current checksums with stored ones, then you know whether the entry has been changed on the server, on the client or both.

Our open-source Rethync SDK lets you implement the above approach quite easily and is available for Android (not for iOS at the moment).

Upvotes: 2

Biraj Zalavadia
Biraj Zalavadia

Reputation: 28484

Best approach is use a time stamp to handle this.

  1. Initial request to server with time stamp value 0.
  2. Server will give the all the data first time with Time-stamp.
  3. Store the Time stamp to sharedpreferences.
  4. In All next request pass the time stamp back to the server
  5. Server will send only those data which are add/update/ after that given time stamp
  6. That is it.

Upvotes: 0

Raghu
Raghu

Reputation: 351

I am doing something similar in my application. I have a last modified date field with each entity that I need to sync. Then periodically, I post this data to the server (actual data + date and time). Now the server can do one of two things. It will check the corresponding data on server side and compare the last modified date. If what the server is latest, it will return the latest data in response. If not, it will update its data and send a response indicating what client has is latest.

Of course you can do several optimization. That is, mark the data as "dirty" so you know whether to even send your data to server. If the phone does not have modified data, your sync is basically getting the latest data from server.

Basically server does the heavy lifting and does all the logic necessary to maintain the latest data on its end and send responses to client appropriately.

Good Luck

Upvotes: 0

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