Can I share same sqlite database from 2 different iOS devices or update one from another?
Not easily. You can sync the db over iCloud but there is a high chance that data will be overwritten.
I recommend writing some sort of syncing tool that can detect and merge changes originating on either device.
A Common method is to use a timestamp column and get all rows modified since the last sync, then update the other database.
You can take a look at OpenMobster's Sync Service. It supports multi-device sync operations with conflict management.
Besides this it supports the following sync modes:
two-way
one-way device
one-way server
bootup
You can run in complete offline mode and the changes will be auto-tracked and synchronized with the network returns. At this time sync happens with the Cloud and other devices that hold the same data that you are holding locally.
The project is located at: http://openmobster.googlecode.com
You can look at the following iOS sync tutorial to get an idea of how this thing works:
http://code.google.com/p/openmobster/wiki/iPhoneSyncApp
Related
I have a mininet (v2.2.2) network with openvswitch (v2.5.2), controlled by OpenDaylight Carbon. My application is an OpenDaylight karaf feature.
The application creates a flow (for multicasts) to a group table (type=all) and adds/removes buckets as needed.
To add/remove buckets, I first check if there is an existing group table:
InstanceIdentifier<Group> groupIid = InstanceIdentifier.builder(Nodes.class)
.child(Node.class, new NodeKey(NodId))
.augmentation(FlowCapableNode.class)
.child(Group.class, grpKey)
.build();
ReadOnlyTransaction roTx = dataBroker.newReadOnlyTransaction();
Future<Optional<Group>> futOptGrp = rwTx.read(LogicalDatastoreType.OPERATIONAL, groupIid);
If it doesn't find the group table, it is created (SalGroupService.addGroup()). If it does find the group table, it is updated (SalGroupService.updateGroup()).
The problem is that it takes some time after the RPC call add/updateGroup() to see the changes in the data model. Waiting for the Future<RPCResult<?>> doesn't guarantee that the data model has the same state as the device.
So, how do I read the group table and bucket list from the data model and make sure that I am indeed reading the same state as the current state of the device?
I know that
Add/UpdateGroupInputBuilder has setTransactionUri()
DataBroker gives transaction to read/write
you should use transaction chaining
But I cannot figure out how to combine these.
Thank you
EDIT: Or do I have to use write transactions in stead of RPC calls?
I dropped using RPC calls for writing flows and switched to using writes to the config datastore. It will still take some time to see the changes appear in the actual device and in the operational datastore but that is ok as long as I use the config datastore for both reads and writes.
However, I have to keep in mind that it is not guaranteed that changes to the config datastore will always make it to the actual device. My flows are not that complicated in the sense that conflicts are unlikely to happen. Still, I will probably check consistency between operational and configuration datastore.
Hye there im going to develop a web system for my final year project using html5 but i am a bit confusing on how am im going to synchronize from the mobile to the server... is there a way to synchronize from mobile (SQL lite) to Administrator(SQL server)... kindly help me regarding this matter
Synchronization can start of simple, but quickly can get rather complex. It all depends on your needs.
Ask yourself the following questions:
do I need to handle deletes? - tombstones/delete flag
is sync one-way or two-way? - backup/copy vs full sync
does anything take more than 100ms a second to save? - date/time issues, or need for overlap
can a record be edited on two devices (or a device and the server) at once? - conflicts
The simple solution is to just use a "lastModified" field and keep track of where you were up to. Remember to use the date/time of the system running the database, so on the device get the current UTC date/time of the server, then get all updates <= to that date/time. Just query for all records since that are newer than you saved date and copy them to the other server.
The more complex solution tracks deletes, handles transactions (started before sync, finishes after sync, missed by simple solution), has advanced conflict resolution, supports batching, etc.
To be even safer you want to stop using date/times and have a global counter for your revisions. This gets even trickier if you want to track updates that have started but not committed their transaction (look at SQL-Server Change Tracking, CHANGE_TRACKING_CURRENT_VERSION()).
More details can be found on Microsoft Sync Framework as one example of how it is done.
Just after some advice and recommendations here if I may.
I'm creating an iPad app (IOS6) that will write data to the local database on the device and then either straight away or later on replicate that record to a web service (so a Cloud service basically).
What is the best way to go about this you think?
I was thinking of just having a column in the local DB called "synced" and set the flag to '0' right away when the record is created, then sync records with a '0' either right away or during regular intervals. Then obviously set the flag to '1' when each record is replicated.
I want the app to work offline and then sync when the device has an available connection to my web service.
Ideally every record should be replicated right away or seconds later, but in the event of no network connectivity I want to be able to queue the replication to occur.
So what's the best way or achieving this you think? Thanks in advance :)
The solution is going to depend a lot on how complex your total solution is.
For example, if the records are only being created on the local device and then uploaded, without ever being modified, then your solution will be more than adequate.
However, if you allow update of the records on the local device or the records can be updated once they get into your web service, then you need to start managing conflict resolution. The way that we address this situation is to record a timestamp in the "master" database (the one updated by the web service) and synchronize that timestamp when a record is uploaded either as a new record or as an update. When the user updates a record, we send the timestamp and if the value in the database is different than the sent database, the update request is rejected. Of course there are different approaches to this conflict resolution, this is just one that works for our application and users.
I use Core Data to maintain a persistent store, and the database can grow quite large. My users with larger databases on iPad 1s don't complete the lightweight migration in time for the process to complete before the app is killed by the iOS for hanging.
What I want to do is every time the server starts up, check to see if the database needs to be migrated (I can't find a method for this on NSPersistentStoreCoordinator), if it does hold the server startup process until the database is upgraded and display a spinner on screen, then move forward with the server startup process once it is. The best way to do this seems to be to add a - (BOOL) upgradeStoreNeedsUpgrade method in the server startup method, but I can't find a way to check. I don't see methods on NSPersistentStoreCoordinator or NSPersistentStore to check the compatibility of a a database at a given URL with a given managed object model.
Is my solution the right way, and if so, how can I check if the managed object model is compatible with the SQLite file at a given URL?
You could try wrapping the core data lightweight migration code in a dispatch block. This should spin it off to a background thread so you can get past the Application Start Watchdog thats probably killing your app. Its either that or you are running the device out of memory.
I sync values from database to local collections as source values and perform operations on these docs subsequently I push updated docs back to the corresponding db table, at success of push I want to pull only those docs from updated database that are not present at local collection of my device.
I could have used sync time stamp but in some peculiar situation either some docs get duplicated or got missing at my device.
I must also bring to notice that the local database also gets augmented while I perform operations at the device.
JSON Store is what you need in this case. More details here -
JSONStore