Crash in fetchAuthValue when App is Resumed from Background

[hschk]

Description

Our Flutter app sometimes crashes when resuming after being in the background for a while. The issue seems to originate from the fetchAuthValue method in the Pusher library. The crash is related to a dynamic cast failure, as seen in the Crashlytics logs (provided below).

I suspect the issue might be caused by an invalid state or incorrect handling of the authorizer object during app lifecycle changes.

Environment Details

• Pusher Library Version: 2.4.0
• Flutter Version: 3.27.1
• Platform: iOS

Crash Logs

Here is the relevant portion of the Crashlytics log:

Crashed: com.apple.main-thread
0  libsystem_kernel.dylib         0xc1d4 __pthread_kill + 8
1  libsystem_pthread.dylib        0x7ef8 pthread_kill + 268
2  libsystem_c.dylib              0x77ad8 abort + 128
3  libswiftCore.dylib             0x3cc1a4 swift::fatalError(unsigned int, char const*, ...) + 134
4  libswiftCore.dylib             0x3bfb44 swift::swift_dynamicCastFailure(swift::TargetMetadata<swift::InProcess> const*, swift::TargetMetadata<swift::InProcess> const*, char const*) + 78
5  pusher_channels_flutter        0x9d88 partial apply for closure #1 in SwiftPusherChannelsFlutterPlugin.fetchAuthValue(socketID:channelName:completionHandler:) + 107 (SwiftPusherChannelsFlutterPlugin.swift:107)

If any additional information is needed, please let us know.
Would appreciate any guidance or fixes from the team. Thanks!

Full Crashlytics Log:

 Crashed: com.apple.main-thread
0  libsystem_kernel.dylib         0xc1d4 __pthread_kill + 8
1  libsystem_pthread.dylib        0x7ef8 pthread_kill + 268
2  libsystem_c.dylib              0x77ad8 abort + 128
3  libswiftCore.dylib             0x3cc1a4 swift::fatalError(unsigned int, char const*, ...) + 134
4  libswiftCore.dylib             0x3cc1c4 swift::warningv(unsigned int, char const*, char*) + 30
5  libswiftCore.dylib             0x3bfb44 swift::swift_dynamicCastFailure(swift::TargetMetadata<swift::InProcess> const*, swift::TargetMetadata<swift::InProcess> const*, char const*) + 78
6  libswiftCore.dylib             0x3bfbc0 swift::_conformsToProtocol(swift::OpaqueValue const*, swift::TargetMetadata<swift::InProcess> const*, swift::TargetProtocolDescriptorRef<swift::InProcess>, swift::TargetWitnessTable<swift::InProcess> const**) + 122
7  libswiftCore.dylib             0x3c4f68 swift_dynamicCastImpl(swift::OpaqueValue*, swift::OpaqueValue*, swift::TargetMetadata<swift::InProcess> const*, swift::TargetMetadata<swift::InProcess> const*, swift::DynamicCastFlags) + 342
8  pusher_channels_flutter        0x9d88 partial apply for closure #1 in SwiftPusherChannelsFlutterPlugin.fetchAuthValue(socketID:channelName:completionHandler:) + 107 (SwiftPusherChannelsFlutterPlugin.swift:107)
9  pusher_channels_flutter        0x5bec thunk for @escaping @callee_guaranteed (@in_guaranteed Any?) -> () + 84 (<compiler-generated>:84)
10 Flutter                        0x5e2468 __54-[FlutterMethodChannel invokeMethod:arguments:result:]_block_invoke + 291 (FlutterChannels.mm:291)
11 Flutter                        0x5a178 std::_fl::__function::__func<fml::internal::CopyableLambda<flutter::PlatformMessageResponseDarwin::Complete(std::_fl::unique_ptr<fml::Mapping, std::_fl::default_delete<fml::Mapping>>)::$_0>, std::_fl::allocator<fml::internal::CopyableLambda<flutter::PlatformMessageResponseDarwin::Complete(std::_fl::unique_ptr<fml::Mapping, std::_fl::default_delete<fml::Mapping>>)::$_0>>, void ()>::operator()() + 24 (platform_message_response_darwin.mm:24)
12 Flutter                        0x85c9c fml::MessageLoopImpl::FlushTasks(fml::FlushType) + 128 (message_loop_impl.cc:128)
13 Flutter                        0x89314 fml::MessageLoopDarwin::OnTimerFire(__CFRunLoopTimer*, fml::MessageLoopDarwin*) + 86 (message_loop_darwin.mm:86)
14 CoreFoundation                 0xb4894 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 32
15 CoreFoundation                 0xb4538 __CFRunLoopDoTimer + 1012
16 CoreFoundation                 0xb408c __CFRunLoopDoTimers + 288
17 CoreFoundation                 0x533b4 __CFRunLoopRun + 1856
18 CoreFoundation                 0x52830 CFRunLoopRunSpecific + 588
19 GraphicsServices               0x11c4 GSEventRunModal + 164
20 UIKitCore                      0x3d2eb0 -[UIApplication _run] + 816
21 UIKitCore                      0x4815b4 UIApplicationMain + 340
22 UIKitCore                      0x7bbfa8 block_destroy_helper.23 + 10212
23 Runner                         0x88cc main + 4343269580 (AppDelegate.swift:4343269580)

[hschk]

I’m not sure if this is related, but when I reopen the app after it has been in the background, I see a series of connection state change logs like this:

flutter: Connection state changed: DISCONNECTED
flutter: Connection state changed: RECONNECTING
flutter: Connection state changed: CONNECTING
flutter: Connection state changed: DISCONNECTED
flutter: Connection state changed: RECONNECTING
flutter: Connection state changed: DISCONNECTED
flutter: Connection state changed: RECONNECTING
flutter: Connection state changed: DISCONNECTED
flutter: Connection state changed: RECONNECTING
flutter: Connection state changed: CONNECTING
flutter: Connection state changed: CONNECTED

Is this expected behavior? As I mentioned, this might not be an issue or even related to the crashes, but I thought it was worth noting while troubleshooting.

[kadersaka]

which version of the pusher channel flutter library r u using?

[hschk]

When I reported this issue, I was using version 2.4.0. However, the same behavior occurs with version 2.5.0.

[kadersaka]

please paste here ur pusher init code and functions. u can also directly message me on kadersaka[at]gmail.com so we can go for a live working session

am suspecting the issue is related to your onAuthorizer code.

[hschk]

Thank you for your response and for offering to help!

I also suspected that the issue might lie within my onAuthorizer code. However, after reviewing our server logs, it appears that our Pusher auth endpoint was returning the expected response with a 200 status code and the correct authentication object at the time of the last crash.

To provide more context, here is my PusherService class implementation:

import 'dart:async';
import 'dart:convert';

import 'package:bridge/business_logic/utilities/locator.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_crashlytics/firebase_crashlytics.dart';
import 'package:flutter_dotenv/flutter_dotenv.dart';
import 'package:logger/logger.dart';
import 'package:pusher_channels_flutter/pusher_channels_flutter.dart';
import 'package:synchronized/synchronized.dart';
import 'package:http/http.dart' as http;

class PusherService {
  // Singleton pattern
  static final PusherService _instance = PusherService._internal();

  factory PusherService() => _instance;

  PusherService._internal();

  final Lock _lock = Lock();
  PusherChannelsFlutter? _pusher;
  bool _isConnected = false;

  final String apiKey = dotenv.env['PUSHER_KEY'] ?? '';
  final String cluster = dotenv.env['PUSHER_CLUSTER'] ?? '';
  final String authEndpoint = dotenv.env['PUSHER_AUTH_ENDPOINT'] ?? '';

  final Logger _logger = getIt<Logger>();

  /// Initializes the Pusher service.
  Future<void> initPusher() async {
    await _lock.synchronized(() async {
      if (_isConnected) return;

      _pusher = PusherChannelsFlutter.getInstance();
      try {
        await _pusher!.init(
          apiKey: apiKey,
          cluster: cluster,
          onAuthorizer: _onAuthorizer,
          onConnectionStateChange: _onConnectionStateChange,
          onError: _onError,
          onSubscriptionSucceeded: _onSubscriptionSucceeded,
          onEvent: _onEvent,
          onSubscriptionError: _onSubscriptionError,
        );
        await _pusher!.connect();
        _isConnected = true;
        _logger.i('Pusher connected successfully.');
      } catch (e, stackTrace) {
        _logger.e('Failed to initialize Pusher',
            error: e, stackTrace: stackTrace);
        FirebaseCrashlytics.instance.recordError(e, stackTrace);
      }
    });
  }

  /// Disconnects from the Pusher service.
  Future<void> disconnect() async {
    if (_isConnected) {
      try {
        await _pusher?.disconnect();
        _isConnected = false;
        _logger.i('Pusher disconnected.');
      } catch (e, stackTrace) {
        _logger.e('Failed to disconnect Pusher',
            error: e, stackTrace: stackTrace);
      }
    }
  }

  /// Subscribes to a Pusher channel.
  Future<PusherChannel> subscribeToChannel(
    String channelName, {
    bool isPrivate = true,
    void Function(PusherEvent event)? onEvent,
  }) async {
    await initPusher();

    final fullChannelName = isPrivate ? 'private-$channelName' : channelName;

    try {
      return await _pusher!.subscribe(
        channelName: fullChannelName,
        onEvent: onEvent != null
            ? (dynamic event) =>
                onEvent(event as PusherEvent) // Typecast auf PusherEvent
            : null,
      );
    } catch (e, stackTrace) {
      _logger.e('Failed to subscribe to channel $fullChannelName',
          error: e, stackTrace: stackTrace);
      rethrow;
    }
  }

  /// Handles authorization for private channels.
  Future<Map<String, String>?> _onAuthorizer(
    String channelName,
    String socketId,
    dynamic options,
  ) async {
    final token = await FirebaseAuth.instance.currentUser?.getIdToken();
    if (token == null) {
      _logger.w('Authorization failed: No token available.');
      return null;
    }

    try {
      final response = await http.post(
        Uri.parse(authEndpoint),
        headers: {
          'Authorization': 'Bearer $token',
        },
        body: {
          'socket_id': socketId,
          'channel_name': channelName,
        },
      );

      if (response.statusCode == 200) {
        return Map<String, String>.from(jsonDecode(response.body));
      } else {
        _logger.w(
          'Authorization failed with status code ${response.statusCode}: ${response.body}',
        );
      }
    } catch (e, stackTrace) {
      _logger.e('Authorization error', error: e, stackTrace: stackTrace);
    }
    return null;
  }

  // Callbacks for Pusher events
  void _onConnectionStateChange(String currentState, String? previousState) {
    _logger.i('Connection state changed: $currentState (from $previousState)');
  }

  void _onError(String message, int? code, dynamic e) {
    _logger.e('Pusher error: $message (Code: $code)', error: e);
  }

  void _onSubscriptionSucceeded(String channelName, dynamic data) {
    _logger.i('Subscription succeeded: $channelName');
  }

  void _onEvent(PusherEvent event) {
    _logger.d('Event received: ${event.data}');
  }

  void _onSubscriptionError(String message, dynamic e) {
    _logger.e('Subscription error: $message', error: e);
  }
}