[firebase_database]: When listening to '.info/connected' and display turns off, the connection state value flaps between true and false

justChris commented 1 month ago

Is there an existing issue for this?

[X] I have searched the existing issues.

Which plugins are affected?

Database

Which platforms are affected?

iOS

Description

When listening to '.info/connected' and display turns off while the app is still in foreground, the connection state value flaps between true and false and is eventually true even though the client has disconnected from the server.

I know the client has disconnected because I'm creating a database entry at the first startup of the app and registering an onDisconnect() callback, which removes this entry from the database when the app disconnects.

So when I turn off the display, the database entry gets removed but the value of the local listener is eventually true.

This way I cannot reliably handle the connection state. Is that a bug? Do you have any suggestions to deal with this behavior?

Reproducing the issue

Just use the sample from https://firebase.google.com/docs/firestore/solutions/presence

Stream<DatabaseEvent> deviceConnectionStatus() {
    try {
      return _firebaseDatabase.ref('.info/connected').onValue;
    } catch (e) {
      debugPrint(e.toString());
      return Stream.error(e);
    }
}

deviceConnectionStatus().listen((event) {
    final isConnected = event.snapshot.value as bool?;
    debugPrint('isConnected: $isConnected');

    if (isConnected == null) return;

    if (isConnected) {
      debugPrint('ONLINE');
      // Logic
    } else {
      debugPrint('OFFLINE');
      // Logic
    }
});

Firebase Core version

3.5.0

Flutter Version

3.24.3

Relevant Log Output

Log output from debugLogs from above code sample:

flutter: isConnected: false
flutter: OFFLINE
flutter: isConnected: true
flutter: ONLINE
flutter: isConnected: false
flutter: OFFLINE
flutter: isConnected: true
flutter: ONLINE

$ flutter doctor -v

[✓] Flutter (Channel stable, 3.24.3, on macOS 15.0 24A335 darwin-arm64, locale en-US)
    • Flutter version 3.24.3 on channel stable at /Users/chris/development/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 2663184aa7 (2 weeks ago), 2024-09-11 16:27:48 -0500
    • Engine revision 36335019a8
    • Dart version 3.5.3
    • DevTools version 2.37.3

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/chris/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.0)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16A242d
    • CocoaPods version 1.15.2

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2024.1)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.11+0-17.0.11b1207.24-11852314)

[✓] VS Code (version 1.93.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.96.0

[✓] Connected device (4 available)
    • Chris’s iPhone (mobile)         • 00008130-000970383EE0001C • ios            • iOS 18.0 22A3354
    • macOS (desktop)                 • macos                     • darwin-arm64   • macOS 15.0 24A335 darwin-arm64
    • Mac Designed for iPad (desktop) • mac-designed-for-ipad     • darwin         • macOS 15.0 24A335 darwin-arm64
    • Chrome (web)                    • chrome                    • web-javascript • Google Chrome 129.0.6668.60

[✓] Network resources
    • All expected network resources are available.

• No issues found!

Flutter dependencies

Expand Flutter dependencies snippet

```yaml Dart SDK 3.5.3 Flutter SDK 3.24.3 cirqles 0.4.0+20 dependencies: - async 2.11.0 [collection meta] - badges 3.1.2 [flutter] - cached_network_image 3.4.1 [cached_network_image_platform_interface cached_network_image_web flutter flutter_cache_manager octo_image] - cloud_firestore 5.4.2 [cloud_firestore_platform_interface cloud_firestore_web collection firebase_core firebase_core_platform_interface flutter meta] - cloud_functions 5.1.2 [cloud_functions_platform_interface cloud_functions_web firebase_core firebase_core_platform_interface flutter] - cupertino_icons 1.0.8 - firebase_analytics 11.3.2 [firebase_analytics_platform_interface firebase_analytics_web firebase_core firebase_core_platform_interface flutter] - firebase_auth 5.3.0 [firebase_auth_platform_interface firebase_auth_web firebase_core firebase_core_platform_interface flutter meta] - firebase_core 3.5.0 [firebase_core_platform_interface firebase_core_web flutter meta] - firebase_crashlytics 4.1.2 [firebase_core firebase_core_platform_interface firebase_crashlytics_platform_interface flutter stack_trace] - firebase_database 11.1.3 [firebase_core firebase_core_platform_interface firebase_database_platform_interface firebase_database_web flutter] - firebase_messaging 15.1.2 [firebase_core firebase_core_platform_interface firebase_messaging_platform_interface firebase_messaging_web flutter meta] - firebase_storage 12.3.1 [firebase_core firebase_core_platform_interface firebase_storage_platform_interface firebase_storage_web flutter] - flutter 0.0.0 [characters collection material_color_utilities meta vector_math sky_engine] - flutter_app_badge_control 0.0.1 [flutter plugin_platform_interface] - flutter_cache_manager 3.4.1 [clock collection file flutter http path path_provider rxdart sqflite uuid] - flutter_linkify 6.0.0 [flutter linkify] - flutter_local_notifications 17.2.3 [clock flutter flutter_local_notifications_linux flutter_local_notifications_platform_interface timezone] - flutter_map 7.0.2 [async collection dart_earcut flutter http latlong2 logger meta polylabel proj4dart vector_math] - flutter_native_splash 2.4.1 [args flutter flutter_web_plugins html image meta path universal_io xml yaml ansicolor] - font_awesome_flutter 10.7.0 [flutter] - geocoding 3.0.0 [flutter geocoding_platform_interface geocoding_android geocoding_ios] - geolocator 13.0.1 [flutter geolocator_platform_interface geolocator_android geolocator_apple geolocator_web geolocator_windows] - hive 2.2.3 [meta crypto] - hive_flutter 1.1.0 [flutter hive path_provider path] - html 0.15.4 [csslib source_span] - http 1.2.2 [async http_parser meta web] - image 4.2.0 [archive meta xml] - image_cropper 8.0.2 [flutter image_cropper_platform_interface image_cropper_for_web] - image_picker 1.1.2 [flutter image_picker_android image_picker_for_web image_picker_ios image_picker_linux image_picker_macos image_picker_platform_interface image_picker_windows] - intl 0.19.0 [clock meta path] - latlong2 0.9.1 [intl] - provider 6.1.2 [collection flutter nested] - rxdart 0.28.0 - shimmer 3.0.0 [flutter] - smooth_page_indicator 1.2.0+3 [flutter] - timeago 3.7.0 [intl] - transparent_image 2.0.1 - url_launcher 6.3.0 [flutter url_launcher_android url_launcher_ios url_launcher_linux url_launcher_macos url_launcher_platform_interface url_launcher_web url_launcher_windows] - uuid 4.5.0 [crypto sprintf meta fixnum] dev dependencies: - build_runner 2.4.12 [analyzer args async build build_config build_daemon build_resolvers build_runner_core code_builder collection crypto dart_style frontend_server_client glob graphs http_multi_server io js logging meta mime package_config path pool pub_semver pubspec_parse shelf shelf_web_socket stack_trace stream_transform timing watcher web_socket_channel yaml] - flutter_lints 5.0.0 [lints] - flutter_test 0.0.0 [flutter test_api matcher path fake_async clock stack_trace vector_math leak_tracker_flutter_testing async boolean_selector characters collection leak_tracker leak_tracker_testing material_color_utilities meta source_span stream_channel string_scanner term_glyph vm_service] - hive_generator 2.0.1 [build source_gen hive analyzer source_helper] dependency overrides: - build_runner 2.4.12 [analyzer args async build build_config build_daemon build_resolvers build_runner_core code_builder collection crypto dart_style frontend_server_client glob graphs http_multi_server io js logging meta mime package_config path pool pub_semver pubspec_parse shelf shelf_web_socket stack_trace stream_transform timing watcher web_socket_channel yaml] - flutter_app_badge_control 0.0.1 [flutter plugin_platform_interface] - font_awesome_flutter 10.7.0 [flutter] - hive_generator 2.0.1 [build source_gen hive analyzer source_helper] transitive dependencies: - _fe_analyzer_shared 72.0.0 [meta] - _flutterfire_internals 1.3.43 [collection firebase_core firebase_core_platform_interface flutter meta] - _macros 0.3.2 - analyzer 6.7.0 [_fe_analyzer_shared collection convert crypto glob macros meta package_config path pub_semver source_span watcher yaml] - ansicolor 2.0.3 - archive 3.6.1 [crypto path] - args 2.5.0 - boolean_selector 2.1.1 [source_span string_scanner] - build 2.4.1 [analyzer async convert crypto glob logging meta package_config path] - build_config 1.1.1 [checked_yaml json_annotation path pubspec_parse yaml] - build_daemon 4.0.2 [built_collection built_value crypto http_multi_server logging path pool shelf shelf_web_socket stream_transform watcher web_socket_channel] - build_resolvers 2.4.2 [analyzer async build collection convert crypto graphs logging package_config path pool pub_semver stream_transform yaml] - build_runner_core 7.3.2 [async build build_config build_resolvers collection convert crypto glob graphs json_annotation logging meta package_config path pool timing watcher yaml] - built_collection 5.1.1 - built_value 8.9.2 [built_collection collection fixnum meta] - cached_network_image_platform_interface 4.1.1 [flutter flutter_cache_manager] - cached_network_image_web 1.3.1 [cached_network_image_platform_interface flutter flutter_cache_manager web] - characters 1.3.0 - checked_yaml 2.0.3 [json_annotation source_span yaml] - clock 1.1.1 - cloud_firestore_platform_interface 6.4.2 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface] - cloud_firestore_web 4.3.1 [_flutterfire_internals cloud_firestore_platform_interface collection firebase_core firebase_core_web flutter flutter_web_plugins] - cloud_functions_platform_interface 5.5.36 [firebase_core flutter meta plugin_platform_interface] - cloud_functions_web 4.10.1 [cloud_functions_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins] - code_builder 4.10.0 [built_collection built_value collection matcher meta] - collection 1.18.0 - convert 3.1.1 [typed_data] - cross_file 0.3.4+2 [meta web] - crypto 3.0.5 [typed_data] - csslib 1.0.0 [source_span] - dart_earcut 1.1.0 - dart_style 2.3.7 [analyzer args collection package_config path pub_semver source_span] - dbus 0.7.10 [args ffi meta xml] - fake_async 1.3.1 [clock collection] - ffi 2.1.3 - file 7.0.0 [meta path] - file_selector_linux 0.9.2+1 [cross_file file_selector_platform_interface flutter] - file_selector_macos 0.9.4+1 [cross_file file_selector_platform_interface flutter] - file_selector_platform_interface 2.6.2 [cross_file flutter http plugin_platform_interface] - file_selector_windows 0.9.3+2 [cross_file file_selector_platform_interface flutter] - firebase_analytics_platform_interface 4.2.4 [_flutterfire_internals firebase_core flutter meta plugin_platform_interface] - firebase_analytics_web 0.5.10+1 [_flutterfire_internals firebase_analytics_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins] - firebase_auth_platform_interface 7.4.6 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface] - firebase_auth_web 5.13.1 [firebase_auth_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins http_parser meta web] - firebase_core_platform_interface 5.3.0 [collection flutter flutter_test meta plugin_platform_interface] - firebase_core_web 2.18.1 [firebase_core_platform_interface flutter flutter_web_plugins meta web] - firebase_crashlytics_platform_interface 3.6.43 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface] - firebase_database_platform_interface 0.2.5+43 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface] - firebase_database_web 0.2.6+1 [collection firebase_core firebase_core_web firebase_database_platform_interface flutter flutter_web_plugins] - firebase_messaging_platform_interface 4.5.45 [_flutterfire_internals firebase_core flutter meta plugin_platform_interface] - firebase_messaging_web 3.9.1 [_flutterfire_internals firebase_core firebase_core_web firebase_messaging_platform_interface flutter flutter_web_plugins meta web] - firebase_storage_platform_interface 5.1.30 [_flutterfire_internals collection firebase_core flutter meta plugin_platform_interface] - firebase_storage_web 3.10.1 [_flutterfire_internals async firebase_core firebase_core_web firebase_storage_platform_interface flutter flutter_web_plugins http meta web] - fixnum 1.1.0 - flutter_local_notifications_linux 4.0.1 [dbus ffi flutter flutter_local_notifications_platform_interface path xdg_directories] - flutter_local_notifications_platform_interface 7.2.0 [flutter plugin_platform_interface] - flutter_plugin_android_lifecycle 2.0.22 [flutter] - flutter_web_plugins 0.0.0 [flutter characters collection material_color_utilities meta vector_math] - frontend_server_client 4.0.0 [async path] - geocoding_android 3.3.1 [flutter geocoding_platform_interface] - geocoding_ios 3.0.1 [flutter geocoding_platform_interface] - geocoding_platform_interface 3.2.0 [flutter meta plugin_platform_interface] - geolocator_android 4.6.1 [flutter geolocator_platform_interface meta uuid] - geolocator_apple 2.3.7 [flutter geolocator_platform_interface] - geolocator_platform_interface 4.2.4 [flutter plugin_platform_interface vector_math meta] - geolocator_web 4.1.1 [flutter flutter_web_plugins geolocator_platform_interface web] - geolocator_windows 0.2.3 [flutter geolocator_platform_interface] - glob 2.1.2 [async collection file path string_scanner] - graphs 2.3.2 [collection] - http_multi_server 3.2.1 [async] - http_parser 4.0.2 [collection source_span string_scanner typed_data] - image_cropper_for_web 6.0.2 [flutter flutter_web_plugins image_cropper_platform_interface web] - image_cropper_platform_interface 7.0.0 [flutter plugin_platform_interface http] - image_picker_android 0.8.12+13 [flutter flutter_plugin_android_lifecycle image_picker_platform_interface] - image_picker_for_web 3.0.5 [flutter flutter_web_plugins image_picker_platform_interface mime web] - image_picker_ios 0.8.12 [flutter image_picker_platform_interface] - image_picker_linux 0.2.1+1 [file_selector_linux file_selector_platform_interface flutter image_picker_platform_interface] - image_picker_macos 0.2.1+1 [file_selector_macos file_selector_platform_interface flutter image_picker_platform_interface] - image_picker_platform_interface 2.10.0 [cross_file flutter http plugin_platform_interface] - image_picker_windows 0.2.1+1 [file_selector_platform_interface file_selector_windows flutter image_picker_platform_interface] - io 1.0.4 [meta path string_scanner] - js 0.7.1 - json_annotation 4.9.0 [meta] - leak_tracker 10.0.5 [clock collection meta path vm_service] - leak_tracker_flutter_testing 3.0.5 [flutter leak_tracker leak_tracker_testing matcher meta] - leak_tracker_testing 3.0.1 [leak_tracker matcher meta] - linkify 5.0.0 - lints 5.0.0 - lists 1.0.1 [meta] - logger 2.4.0 - logging 1.2.0 - macros 0.1.2-main.4 [_macros] - matcher 0.12.16+1 [async meta stack_trace term_glyph test_api] - material_color_utilities 0.11.1 [collection] - meta 1.15.0 - mgrs_dart 2.0.0 [unicode] - mime 1.0.6 - nested 1.0.0 [flutter] - octo_image 2.1.0 [flutter] - package_config 2.1.0 [path] - path 1.9.0 - path_provider 2.1.4 [flutter path_provider_android path_provider_foundation path_provider_linux path_provider_platform_interface path_provider_windows] - path_provider_android 2.2.10 [flutter path_provider_platform_interface] - path_provider_foundation 2.4.0 [flutter path_provider_platform_interface] - path_provider_linux 2.2.1 [ffi flutter path path_provider_platform_interface xdg_directories] - path_provider_platform_interface 2.1.2 [flutter platform plugin_platform_interface] - path_provider_windows 2.3.0 [ffi flutter path path_provider_platform_interface] - petitparser 6.0.2 [meta] - platform 3.1.5 - plugin_platform_interface 2.1.8 [meta] - polylabel 1.0.1 [collection] - pool 1.5.1 [async stack_trace] - proj4dart 2.1.0 [mgrs_dart wkt_parser meta] - pub_semver 2.1.4 [collection meta] - pubspec_parse 1.3.0 [checked_yaml collection json_annotation pub_semver yaml] - shelf 1.4.1 [async collection http_parser path stack_trace stream_channel] - shelf_web_socket 2.0.0 [shelf stream_channel web_socket_channel] - sky_engine 0.0.99 - source_gen 1.5.0 [analyzer async build dart_style glob path source_span yaml] - source_helper 1.3.4 [analyzer collection source_gen] - source_span 1.10.0 [collection path term_glyph] - sprintf 7.0.0 - sqflite 2.3.3+1 [flutter sqflite_common path] - sqflite_common 2.5.4+3 [synchronized path meta] - stack_trace 1.11.1 [path] - stream_channel 2.1.2 [async] - stream_transform 2.1.0 - string_scanner 1.2.0 [source_span] - synchronized 3.3.0+2 - term_glyph 1.2.1 - test_api 0.7.2 [async boolean_selector collection meta source_span stack_trace stream_channel string_scanner term_glyph] - timezone 0.9.4 [path] - timing 1.0.1 [json_annotation] - typed_data 1.3.2 [collection] - unicode 0.3.1 [lists] - universal_io 2.2.2 [collection meta typed_data] - url_launcher_android 6.3.10 [flutter url_launcher_platform_interface] - url_launcher_ios 6.3.1 [flutter url_launcher_platform_interface] - url_launcher_linux 3.2.0 [flutter url_launcher_platform_interface] - url_launcher_macos 3.2.1 [flutter url_launcher_platform_interface] - url_launcher_platform_interface 2.3.2 [flutter plugin_platform_interface] - url_launcher_web 2.3.3 [flutter flutter_web_plugins url_launcher_platform_interface web] - url_launcher_windows 3.1.2 [flutter url_launcher_platform_interface] - vector_math 2.1.4 - vm_service 14.2.5 - watcher 1.1.0 [async path] - web 1.1.0 - web_socket 0.1.6 [web] - web_socket_channel 3.0.1 [async crypto stream_channel web web_socket] - wkt_parser 2.0.0 - xdg_directories 1.0.4 [meta path] - xml 6.5.0 [collection meta petitparser] - yaml 3.1.2 [collection source_span string_scanner] ```

Additional context and comments

No response

SelaseKay commented 1 month ago

Hi @justChris , thanks for submitting this report. I am able to reproduce this issue. We will investigate further and provide feedback. Thanks!

justChris commented 1 month ago

I forgot to mention, that when the display turns back on, the isConnected value is not being updated at all.

In my opinion, the expected behavior would be:

display turns off isConnected -> false
display turns on isConnected -> true

SelaseKay commented 1 month ago

Hi @justChris , I’ve tested this issue with the latest version of firebase_database but wasn’t able to reproduce it. Could you update to the latest version and give it another try?

justChris commented 1 month ago

Hi @justChris , thanks for submitting this report. I am able to reproduce this issue. We will investigate further and provide feedback. Thanks!

@SelaseKay here you said you could reproduce the issue. Did you then update the package which fixed the issue?

SelaseKay commented 1 month ago

Correct. I could reproduce this issue initially on an older version. Updating the packages seems to resolve the issue on my end.

justChris commented 1 month ago

@SelaseKay I have tested it and the flapping as well as the wrong eventual connection state is gone.

Now the listener does not fire at all when the display turns off. Also the Database entry does not get removed immediately when display turns off. It seems iOS does not immediately cut the connection anymore when display turns off.

I have the feeling it works more like android does now.

I still have to test how it is behaving now when display turns off and then the internet connection is lost on the device.

I assume the database entry gets removed like expected, but I have to check how the local listener behaves.

I will give feedback.

justChris commented 1 month ago

@SelaseKay I have tested it now and it seems to be working as expected finally.

When I turn off the display, the listener does not fire at all and the Database Entry does not get removed as I described before. When I set my device to airplane mode then, the listener fires immediately as expected (log output below) and the Database entry gets removed after a while, when the onDisconnect callback fires.

Log Output:

flutter: isConnected: false
flutter: OFFLINE

Now everything seems to be working as expected and this issue can be closed. Thank you @SelaseKay for your professional and kind support.

justChris commented 1 month ago

After a little more testing, I noticed that the listener's behavior differs from debug to release mode. I added a small debug box in my app to demonstrate that.

In debug mode on initial app start the listeners fires false and again true. When I turn off the display, the listener does not fire again neither it does when the display turns back on.

In release mode on initial app start the listeners fires false and again true as well as in debug mode. When I turn off the display, the listener does not fire as well as in debug mode.

But when I turn the display back on, the listener fires false and then true.

Anyways this seems to be correct and I can work with this behavior. I just wanted to share this information with you.

justChris commented 1 month ago

I let this debug box in place for a while and used and tested my app. I noticed that sometimes there is still a flapping when I turn the display back on. This seems to happen randomly. When the flapping happens it fires false, true, false, true.

Since I create a database entry and register a onDisconnect callback every time the isConnected value is true this flapping left me a zombie entry, which will never be deleted.

So this is unfortunately still not reliable. Somehow I have to debounce this flapping myself.

Just wanted to let you know in case you want to reproduce this behavior @SelaseKay

SelaseKay commented 1 month ago

I suspect this behaviour could be coming from the native sdk which I believe is intended. For more clarification, it would be best to raise this on firebase-ios-sdk.

justChris commented 1 month ago

I will do that, thank you.

justChris commented 1 month ago

This issue will be further investigated in https://github.com/firebase/firebase-ios-sdk/issues/13877

firebase / flutterfire