Bad Realm file header (#3)

[AlexTip]

Hi there! We've got growing Realm exception (kinda about 17k crashes from about 800 users for the last 30 days) with the next stack trace:

Fatal Exception: io.realm.exceptions.RealmFileException: Unable to open a realm at path '/data/data/com.package.name/files/db.realm': Bad Realm file header (#3). (Bad Realm file header (#3)) (/data/data/com.package.name/files/db.realm) in /home/cc/repo/realm/release/realm/realm-library/src/main/cpp/io_realm_internal_SharedRealm.cpp line 217
       at io.realm.internal.SharedRealm.nativeGetSharedRealm(SharedRealm.java)
       at io.realm.internal.SharedRealm.(SharedRealm.java)
       at io.realm.internal.SharedRealm.getInstance(SharedRealm.java:237)
       at io.realm.internal.SharedRealm.getInstance(SharedRealm.java:206)
       at io.realm.RealmCache.createRealmOrGetFromCache(RealmCache.java:127)
       at io.realm.Realm.getDefaultInstance(Realm.java:266)

Device stats (fairly no pattern): https://prnt.sc/g3ryyh
The only thing to mention is that crashing scenario is happening from new thread invoked from the service.

[beeender]

1. What is your Realm version? Does the crash happen to a specific Realm version?
2. Do you use encryption?
3. Do you open Realm from multiple processes?

[AlexTip]

1. Realm version - 3.5.0, crash reproduced in latest version 3.2+
2. No
3. No

[beeender]

Does it happen when you update the Realm from the older version to 3.5.0? If yes, what is the old version?

[AlexTip]

As far as I can see this crash was persistent for all the time in minor volumes about 10 crashes a day, but when we updated 3.1.4 to 3.4.0 and further the number of crashes started to grow incredibly.

[beeender]

Do you use Realm.compactRealm()?

[AlexTip]

No, the configuration is trivial enough

RealmConfiguration.Builder()
                .name(DATABASE_NAME)
                .schemaVersion(DATABASE_VERSION)
                .migration(new Migration())
                .build()

No additional features are used

[beeender]

Should be the same issue with realm/realm-core#2258 let's discuss there.

[Zhuinden]

Technically "bad Realm file header" means corruption, but you currently don't seem to be doing anything that ought to cause corruption.

I guess the next question is:

• how many threads try to start transaction concurrently (shouldn't cause a problem but hey), for example are Realm writes on a dedicated Realm-write-thread, or in AsyncTask/other threadpools

• do you have two or more processes in your app,

• is there a chance that you have multiple process AND execute migration in multiple processes at once by accident? (for example first Realm is opened inside Application class, and you have two processes)

[cmelchior]

@AlexTip Are you compacting your Realm at any point. We are seeing other reports that if it fails it appears to corrupt the original file: #5011

EDIT: Ups, it appears that @beeender already asked that. Ignore me

[cmelchior]

Closing due to no response.

[ozv101]

@cmelchior @beeender im seeing a few of these similiar issues opened and it seems like no one can reproduce them. is this something we're going to have to live with?

[Zhuinden]

@ozv101 realm version, error / exception stack trace

[ozv101]

@Zhuinden #5629