In my latest app update I have a few users complaining about crashes and I managed to get my hands on a crash report. Here's the crash reason from the symbolicated crash log.
Exception Type: EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Termination Reason: Namespace SPRINGBOARD, Code 0x8badf00d
Triggered by Thread: 0
This happens when I call [NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:]
Here's the complete stacktrace:
Thread 0 name: Dispatch queue: SQLQueue 0x12fecca10 for .database.db.migrationdestination_41b5a6b5c6e848c462a8480cd24caef3
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x0000000180640164 __fcntl + 8
1 libsystem_kernel.dylib 0x0000000180625660 fcntl + 84
2 libsqlite3.dylib 0x0000000181ba3f90 0x181b3d000 + 421776
3 libsqlite3.dylib 0x0000000181bb9e50 0x181b3d000 + 511568
4 libsqlite3.dylib 0x0000000181bcdf34 0x181b3d000 + 593716
5 libsqlite3.dylib 0x0000000181bcdd98 sqlite3_wal_checkpoint_v2 + 492
6 libsqlite3.dylib 0x0000000181ba41b0 0x181b3d000 + 422320
7 libsqlite3.dylib 0x0000000181b7b288 sqlite3_step + 976
8 CoreData 0x000000018391b194 _execute + 164
9 CoreData 0x000000018394ffd8 -[NSSQLiteConnection commitTransaction] + 312
10 CoreData 0x0000000183a6ced8 __43-[_NSSQLiteStoreMigrator performMigration:]_block_invoke + 2784
11 CoreData 0x0000000183a36cbc __37-[NSSQLiteConnection performAndWait:]_block_invoke + 40
12 libdispatch.dylib 0x00000001804fe9a0 _dispatch_client_callout + 16
13 libdispatch.dylib 0x000000018050bee0 _dispatch_barrier_sync_f_invoke + 84
14 CoreData 0x0000000183a36c08 -[NSSQLiteConnection performAndWait:] + 144
15 CoreData 0x0000000183a6c35c -[_NSSQLiteStoreMigrator performMigration:] + 184
16 CoreData 0x0000000183a63db0 -[NSSQLiteInPlaceMigrationManager migrateStoreFromURL:type:options:withMappingModel:toDestinationURL:destinationType:destinationOptions:error:] + 1912
17 CoreData 0x00000001839ee814 -[NSMigrationManager migrateStoreFromURL:type:options:withMappingModel:toDestinationURL:destinationType:destinationOptions:error:] + 556
18 CoreData 0x0000000183a5f090 -[NSStoreMigrationPolicy(InternalMethods) migrateStoreAtURL:toURL:storeType:options:withManager:error:] + 324
19 CoreData 0x0000000183a5e3ec -[NSStoreMigrationPolicy migrateStoreAtURL:withManager:metadata:options:error:] + 120
20 CoreData 0x0000000183a5fb08 -[NSStoreMigrationPolicy(InternalMethods) _gatherDataAndPerformMigration:] + 2440
21 CoreData 0x00000001839fc188 __91-[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:]_block_invoke + 4160
22 CoreData 0x0000000183a08630 gutsOfBlockToNSPersistentStoreCoordinatorPerform + 168
23 libdispatch.dylib 0x00000001804fe9a0 _dispatch_client_callout + 16
24 libdispatch.dylib 0x000000018050bee0 _dispatch_barrier_sync_f_invoke + 84
25 CoreData 0x00000001839f7d70 _perform + 200
26 CoreData 0x000000018390d5e4 -[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:] + 388
I don't have more details on the crash. Only that it happens for a few users and not all. I have no idea how to reproduce it for a proper fix. The user reported that the app started, was "frozen" for some time and then it crashed. And it keeps doing so.
I had a look at the last version of the core-data model since I shipped the app and this file is still the exact same. During development I added 5 more versions in-between but that shouldn't be a problem right? The version shipped in the app before the update is untouched...
EDIT: The changes I made to the model were simply adding some new properties on existing entities. But if auto-migration would fail, it would fail for everybody, right? Not only for a few users?!?
So I was hoping somebody here already might had the same issue and a solution on how to fix it. Or at least a way on how to detect the problem without the app crashing. Then I could just recreate the DB for those users...
Core-data migrations can take time. If it takes too long for your first view to load then the watchdog will kick in a kill your app. This can happen when you user has much more data than you expect. Instead add a migration checker. And if you need to do a migration then show a loading UI with a loading animation while you load the store.
-(BOOL) storeNeedsMigrationAtURL:(NSString*) sourceStorePath{
if (![[NSFileManager defaultManager] fileExistsAtPath:sourceStorePath]) {
// Database doesn't yet exist. No need to test data compatibility"
return NO;
}
NSManagedObjectModel *model = [[NSManagedObjectModel alloc] initWithContentsOfURL:"<Your models directory name>" ];
NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
NSError *error = nil;
NSURL *sourceStoreURL = [NSURL fileURLWithPath:sourceStorePath];
NSDictionary *sourceStoreMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:sourceStoreURL options:nil error:&error];
// Do error checking... Removed from the code sample.
NSManagedObjectModel *destinationModel = [psc managedObjectModel];
BOOL isCompatible = [destinationModel isConfiguration:nil
compatibleWithStoreMetadata:sourceStoreMetadata];
return isCompatible;
}
see https://vimeo.com/89370886 around 55 minutes you can also read https://hamishrickerby.com/2012/06/04/core-data-migrations-and-large-data-sets/