Crash in Realm Sync, realm::SyncSession::handle_location_update_failed, realm_core_v_13_26_0 about realm-swift HOT 11 CLOSED

➤ PM Bot commented:

Jira ticket: RCOCOA-2302

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@michael-wb can you take a look at this one?

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➤ michael-wb commented:

This looks like it is related to RCORE-1982 that I am currently working on. The error reported by core is not fatal, but the sync session will not attempt to reconnect. Both of these will be addressed.

The current workaround is to is to ignore the error for now and the reconnect should occur (at least on Cocoa) once the device is connected to the network.

from realm-swift.

I think the problem is that we're hitting an assertion failure in handle_location_update_failed, so there's no obvious way to ignore the error here.

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Thanks all! We've received more information from users, and it seems to be occurring when a network connection appears to exist (local wifi), but that connection may be restricted to most outside sources. Unfortunately this is fairly common use case for our users, so it's quite impactful at the moment.

It looks like the assertion was introduced in realm-core 13.26.0 in this commit.

I was wondering if it would be safe for a production app to rollback from Realm Swift v10.47 to v10.45.3, reverting to the previous version of realm-core?

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➤ michael-wb commented:

Thanks for the update - the error happens any time the location update fails (e.g. no internet) when a realm is opened. One workaround is to capture the error and just ignore it, as described from a different ticket (copied below). A fix is in progress and I am currently adding tests to verify.

{quote}
If they keep using 10.45.3 (https://github.com/realm/realm-swift/releases/tag/v10.45.3)
A workaround on the meantime is to ignore connection errors while we work on a fix for this, there is already a Core ticket for it https://jira.mongodb.org/browse/RCORE-1982.
An example of the code
{quote}

app.syncManager.errorHandler = { syncError, syncSession in
   if let syncError = syncError as? SyncError {
      if syncError.code == .connectionFailed {
          return
      }
      self.error = syncError
   }
} 

{quote}
This will hide the error message while offline. The sync session will be resumed when the device goes online without the need of any extra code (Like previous behaviour).
{quote}

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That doesn't appear to be our experience. No sync error is reported, and the application is killed from the realm sync thread.

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➤ michael-wb commented:

Sorry for the inconvenience this has caused.
Are you able to tell if the crash is coming from this line? (fwiw - the handle_location_update_failed function this is part of is being removed as part of the fix):
https://github.com/realm/realm-core/blob/master/src/realm/object-store/sync/sync_session.cpp#L253
REALM_ASSERT(m_state == State::WaitingForAccessToken);

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It seems likely. The next call in the stack trace is to realm::util::terminate, which would track with that REALM_ASSERT macro. Is it possible to disable assertions from the Realm Swift SDK (installed via CocoaPods)?

I'm also happy to rollback to v10.45.3 for a while if there wouldn't be any compatibility issues with apps that had already been running v10.47

from realm-swift.

Hi @gyratorycircus,
This has been updated in the Swift SDK v10.49.1 (based on Realm v14.4.1) to no longer throw the fatal error if the location update fails while offline. However, there is still an outstanding issue (realm/realm-core#7527) regarding @AutoOpen, where it will not exit the .connecting state if the location needs to be updated and the client is offline. There is a fix for this issue in review and will be merged shortly.

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@gyratorycircus - Sorry for the delay, the Realm Swift v10.50.0 release includes a fix (in Realm Core PR #7528) that is part of Core v16.5.2 so the @AutoOpen class so it will fall through and open the local realm if the asynchronous sync/update is not able to successfully update the realm (e.g. currently offline).

Please reopen this ticket or file a new one if you find that it is still not working for you.

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