🐛 [firebase_database] The 'plugins.flutter.io/firebase_database' channel sent a message from native to Flutter on a non-platform thread. Platform channel messages must be sent on the platform thread. While using runTransaction

[MirceaX2Mobile]

Bug report

Describe the bug
While using firebase_database on iOS 17 (Xcode15) on runTransaction on real time database I'm getting this warning in console:

[VERBOSE-2:shell.cc(1004)] The 'plugins.flutter.io/firebase_database' channel sent a message from native to Flutter on a non-platform thread. Platform channel messages must be sent on the platform thread. Failure to do so may result in data loss or crashes, and must be fixed in the plugin or application code creating that channel.
See https://docs.flutter.dev/platform-integration/platform-channels#channels-and-platform-threading for more information.

Steps to reproduce

Steps to reproduce the behaviour:

1. Add the latest pub firebase_database
   firebase_database: ^10.2.6

2. Run a simple transaction request to the firebase database

  final dbRef = FirebaseDatabase.instance.ref();
  updateAnalytics() {
    dbRef
        .child("analytics")
        .child("number")
        .runTransaction((Object? oldValue) {
        if (oldValue == null) {
          return Transaction.success(1);
        }
        int _newValue = (oldValue as int? ?? 0) + 1;
        return Transaction.success(_newValue);
    });
  }

Expected behavior

Use the plugin without getting warnings in the console.

Additional context

Run using iPhone 15 Pro iOS 17
Xcode 15
Flutter 3.13.5 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 12fccda598 (4 days ago) • 2023-09-19 13:56:11 -0700
Engine • revision bd986c5ed2
Tools • Dart 3.1.2 • DevTools 2.25.0

Flutter doctor

Run flutter doctor and paste the output below:

Click To Expand

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.13.5, on macOS 13.5.2 22G91 darwin-arm64, locale
    en-GB)
[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 15.0)
[✓] Android Studio (version 2022.2)
[✓] Connected device (3 available)
[✓] Network resources

• No issues found!

Solution

I found a fix. The error is triggered because channel handlers are not executed on background threads. If you go the FLTFirebaseDatabasePlugin file inside the method - (void)databaseRunTransaction:(id)arguments withMethodCallResult:(FLTFirebaseMethodCallResult *)result {
the cannel handler is not running on the main thread.

        [strongSelf->_channel invokeMethod:@"FirebaseDatabase#callTransactionHandler"
                                 arguments:@{
                                   @"transactionKey" : @(transactionKey),
                                   @"snapshot" : @{
                                     @"key" : currentData.key ?: [NSNull null],
                                     @"value" : currentData.value ?: [NSNull null],
                                   }
                                 }
                                    result:methodCallResultHandler];

In order to fix this we need to add dispatch_async and the warning is not shown anymore.

      dispatch_async(dispatch_get_main_queue(), ^{
          [strongSelf->_channel invokeMethod:@"FirebaseDatabase#callTransactionHandler"
                                   arguments:@{
                                     @"transactionKey" : @(transactionKey),
                                     @"snapshot" : @{
                                       @"key" : currentData.key ?: [NSNull null],
                                       @"value" : currentData.value ?: [NSNull null],
                                     }
                                   }
                                      result:methodCallResultHandler];
      });

[danagbemava-nc]

Reproducible using the firebase_database sample app.

Launching lib/main.dart on iPhone 15 Pro in debug mode...
Warning: Missing build name (CFBundleShortVersionString).
Warning: Missing build number (CFBundleVersion).
Action Required: You must set a build name and number in the pubspec.yaml file version field before submitting to the App Store.
Xcode build done.                                           80.1s
[VERBOSE-2:FlutterDarwinContextMetalImpeller.mm(37)] Using the Impeller rendering backend.
Connecting to VM Service at ws://127.0.0.1:50261/excrZu0Jum8=/ws
flutter: [firebase_database/permission-denied] Client doesn't have permission to access the desired data.
[VERBOSE-2:shell.cc(1004)] The 'plugins.flutter.io/firebase_database' channel sent a message from native to Flutter on a non-platform thread. Platform channel messages must be sent on the platform thread. Failure to do so may result in data loss or crashes, and must be fixed in the plugin or application code creating that channel.
See https://docs.flutter.dev/platform-integration/platform-channels#channels-and-platform-threading for more information.

\cc @russellwheatley

[MirceaX2Mobile]

Any updates on this?

[russellwheatley]

I've created a PR: #11628

[MirceaX2Mobile]

@russellwheatley Oh great! So my assumptions were correct!

[Allansekyewa]

The 'plugins.flutter.io/firebase_storage' channel sent a message from native to Flutter on a non-platform thread. Platform channel messages must be sent on the platform thread. Failure to do so may result in data loss or crashes, and must be fixed in the plugin or application code creating that channel. help with this