CODEWITHSUNDEEP
androidapisqliterestclient
Madoc
Madoc

Reputation: 33

Handle synchronisation of data between Android Service and Server via REST API

I am trying to design how to best handle synchronisation of data between an Android application and a remote server through a REST API.

Now it is still early stage but I have my rest server basically running (enough for testing purpose anyway).

I have 3 tables to synchronise (linked as below).

SHOW >----- SEASON >----- EPISODE

Both server and device have a similar version of these tables and I need to synchronise them FROM device to SERVER (for now and eventually 2 ways). The synchronisation will happen through an Android service making asynchronous calls to the REST API (insert/update and delete) in the background.

Now my main issue is coming up with a logic that will ensure both sides will get updated accordingly.

insert/update from device to server will be done through a POST request so I thought of having a state flag on all 3 tables that gets populated via ON INSERT/ON UPDATE TRIGGERS (SQlite) allowing the Synchronisation service to work out rows that need to go on the server. Is that the correct approach ?

It would look something like

CREATE TRIGGER sync_update_show AFTER UPDATE ON show
BEGIN
    UPDATE show SET sync_flag = 'TO_SYNC' WHERE _id = new._id
END

Now for deletion, the service being independent from the main app I though of using BEFORE DELETE SQlite TRIGGERS to populate a "TODELETE" table that the service can browse and trigger delete api calls to the server. Is that the correct approach ?

It would look something like

CREATE TRIGGER sync_delete_show BEFORE DELETE ON show
BEGIN
    INSERT INTO todelete_show
    SELECT * FROM show WHERE _id = old._id
END

Now when it comes to the server to app sync I would just get all records (APi call) and handle the insert/update/delete on the device (browsing through the returned records). But there may be a more efficient approach optimising the bandwidth (the returned JSON might be big).

I welcome any input on that as I do not want to start working on the Service implementation and realise I got it all wrong !

Upvotes: 3

Views: 3589

Answers (2)

openmobster
openmobster

Reputation: 1027

Your approach of managing the changelog using database triggers will definitely work. If you want a more object oriented approach you could expose a CRUD API for your business object and then within the API update a changelog table with update/insert/delete markers and not use database triggers.

In case you are interested in using a Sync Framework I would like to draw your attention to OpenMobster's Sync Service.

You can do the following sync operations

  • two-way
  • one-way client
  • one-way device
  • bootup

Besides that, all modifications are automatically tracked and synced with the Cloud. You can have your app offline when network connection is down. It will track any changes and automatically in the background synchronize it with the cloud when the connection returns.

It also supports sync across multiple devices like iCloud does.

On the Cloud, you just have to write a Java Channel which is a CRUD interface to your data and expose the channel to the Sync Engine. On the device side this data is then available through a CRUD based Sync API. All other Synchronization details like managing the changelog, conflict management, replication to multiple devices, etc are automatically handled by the Sync Engine.

In your case,

the ChangeLog is automatically managed and integrated with the Sync Engine. It uses the object oriented approach I mentioned and Synchronization is handled through a CRUD based Sync API.

Here is a link to the open source project: http://openmobster.googlecode.com

Here is a tutorial to understand some of its workings: http://code.google.com/p/openmobster/wiki/AndroidSyncApp

Upvotes: 1

Julian Suarez
Julian Suarez

Reputation: 4521

I think your approach using triggers could definitively work, I suggest you use a single "SYNC" table to record all the network operations that you need to make, so that even if you're offline all network operations are scheduled to be executed when possible, and after you have executed a task delete it from the "SYNC" table.

I strongly suggest you implement a ContentProvider to store your tables since you can more easily leverage a lot of Android APIs in your activities/fragments, especially the CursorLoaders and CursorAdapters.

Take a look at contentProviders : http://developer.android.com/guide/topics/providers/content-provider-creating.html

And also take a look at SyncAdapter: http://developer.android.com/reference/android/content/AbstractThreadedSyncAdapter.html

Also check out this talk about bulding restful apps on android, is a bit old but I think it is still very valid http://www.google.com/events/io/2010/sessions/developing-RESTful-android-apps.html

Upvotes: 0

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