fix: isolate freeze app on older ios device

mobile/lib/domain/services/background_worker.service.dart

@@ -30,9 +30,9 @@ import 'package:immich_mobile/services/upload.service.dart';
 import 'package:immich_mobile/utils/bootstrap.dart';
 import 'package:immich_mobile/utils/debug_print.dart';
 import 'package:immich_mobile/utils/http_ssl_options.dart';
+import 'package:immich_mobile/wm_executor.dart';
 import 'package:isar/isar.dart';
 import 'package:logging/logging.dart';
-import 'package:worker_manager/worker_manager.dart';
 
 class BackgroundWorkerFgService {
   final BackgroundWorkerFgHostApi _foregroundHostApi;
@@ -94,7 +94,7 @@ class BackgroundWorkerBgService extends BackgroundWorkerFlutterApi {
       await Future.wait(
         [
           loadTranslations(),
-          workerManager.init(dynamicSpawning: true),
+          workerManagerPatch.init(dynamicSpawning: true),
           _ref?.read(authServiceProvider).setOpenApiServiceEndpoint(),
           // Initialize the file downloader
           FileDownloader().configure(
@@ -193,7 +193,7 @@ class BackgroundWorkerBgService extends BackgroundWorkerFlutterApi {
       _logger.info("Cleaning up background worker");
       final cleanupFutures = [
         nativeSyncApi?.cancelHashing(),
-        workerManager.dispose().catchError((_) async {
+        workerManagerPatch.dispose().catchError((_) async {
           // Discard any errors on the dispose call
           return;
         }),

mobile/lib/main.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 import 'dart:io';
+import 'dart:math';
 
 import 'package:auto_route/auto_route.dart';
 import 'package:background_downloader/background_downloader.dart';
@@ -40,10 +41,10 @@ import 'package:immich_mobile/utils/debug_print.dart';
 import 'package:immich_mobile/utils/http_ssl_options.dart';
 import 'package:immich_mobile/utils/licenses.dart';
 import 'package:immich_mobile/utils/migration.dart';
+import 'package:immich_mobile/wm_executor.dart';
 import 'package:intl/date_symbol_data_local.dart';
 import 'package:logging/logging.dart';
 import 'package:timezone/data/latest.dart';
-import 'package:worker_manager/worker_manager.dart';
 
 void main() async {
   ImmichWidgetsBinding();
@@ -52,7 +53,7 @@ void main() async {
   await Bootstrap.initDomain(isar, drift, logDb);
   await initApp();
   // Warm-up isolate pool for worker manager
-  await workerManager.init(dynamicSpawning: true);
+  await workerManagerPatch.init(dynamicSpawning: true, isolatesCount: max(Platform.numberOfProcessors - 1, 5));
   await migrateDatabaseIfNeeded(isar, drift);
   HttpSSLOptions.apply();
 

mobile/lib/utils/isolate.dart

@@ -11,6 +11,7 @@ import 'package:immich_mobile/providers/infrastructure/db.provider.dart';
 import 'package:immich_mobile/utils/bootstrap.dart';
 import 'package:immich_mobile/utils/debug_print.dart';
 import 'package:immich_mobile/utils/http_ssl_options.dart';
+import 'package:immich_mobile/wm_executor.dart';
 import 'package:logging/logging.dart';
 import 'package:worker_manager/worker_manager.dart';
 
@@ -31,7 +32,7 @@ Cancelable<T?> runInIsolateGentle<T>({
     throw const InvalidIsolateUsageException();
   }
 
-  return workerManager.executeGentle((cancelledChecker) async {
+  return workerManagerPatch.executeGentle((cancelledChecker) async {
     T? result;
     await runZonedGuarded(
       () async {

mobile/lib/wm_executor.dart

@@ -0,0 +1,251 @@
+// part of 'package:worker_manager/worker_manager.dart';
+// ignore_for_file: implementation_imports, avoid_print
+
+import 'dart:async';
+import 'dart:math';
+
+import 'package:collection/collection.dart';
+import 'package:flutter/foundation.dart';
+import 'package:worker_manager/src/number_of_processors/processors_io.dart';
+import 'package:worker_manager/src/worker/worker.dart';
+import 'package:worker_manager/worker_manager.dart';
+
+final workerManagerPatch = _Executor();
+
+// [-2^54; 2^53] is compatible with dart2js, see core.int doc
+const _minId = -9007199254740992;
+const _maxId = 9007199254740992;
+
+class Mixinable<T> {
+  late final itSelf = this as T;
+}
+
+mixin _ExecutorLogger on Mixinable<_Executor> {
+  var log = false;
+
+  @mustCallSuper
+  void init() {
+    logMessage("${itSelf._isolatesCount} workers have been spawned and initialized");
+  }
+
+  void logTaskAdded<R>(String uid) {
+    logMessage("added task with number $uid");
+  }
+
+  @mustCallSuper
+  void dispose() {
+    logMessage("worker_manager have been disposed");
+  }
+
+  @mustCallSuper
+  void _cancel(Task task) {
+    logMessage("Task ${task.id} have been canceled");
+  }
+
+  void logMessage(String message) {
+    if (log) print(message);
+  }
+}
+
+class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
+  final _queue = PriorityQueue<Task>();
+  final _pool = <Worker>[];
+  var _nextTaskId = _minId;
+  var _dynamicSpawning = false;
+  var _isolatesCount = numberOfProcessors;
+
+  @override
+  Future<void> init({int? isolatesCount, bool? dynamicSpawning}) async {
+    if (_pool.isNotEmpty) {
+      print("worker_manager already warmed up, init is ignored. Dispose before init");
+      return;
+    }
+    if (isolatesCount != null) {
+      if (isolatesCount < 0) {
+        throw Exception("isolatesCount must be greater than 0");
+      }
+
+      _isolatesCount = isolatesCount;
+    }
+    _dynamicSpawning = dynamicSpawning ?? false;
+    await _ensureWorkersInitialized();
+    super.init();
+  }
+
+  @override
+  Future<void> dispose() async {
+    _queue.clear();
+    for (final worker in _pool) {
+      worker.kill();
+    }
+    _pool.clear();
+    super.dispose();
+  }
+
+  Cancelable<R> execute<R>(Execute<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
+    return _createCancelable<R>(execution: execution, priority: priority);
+  }
+
+  Cancelable<R> executeNow<R>(ExecuteGentle<R> execution) {
+    final task = TaskGentle<R>(
+      id: "",
+      workPriority: WorkPriority.immediately,
+      execution: execution,
+      completer: Completer<R>(),
+    );
+
+    Future<void> run() async {
+      try {
+        final result = await execution(() => task.canceled);
+        task.complete(result, null, null);
+      } catch (error, st) {
+        task.complete(null, error, st);
+      }
+    }
+
+    run();
+    return Cancelable(completer: task.completer, onCancel: () => _cancel(task));
+  }
+
+  Cancelable<R> executeWithPort<R, T>(
+    ExecuteWithPort<R> execution, {
+    WorkPriority priority = WorkPriority.immediately,
+    required void Function(T value) onMessage,
+  }) {
+    return _createCancelable<R>(
+      execution: execution,
+      priority: priority,
+      onMessage: (message) => onMessage(message as T),
+    );
+  }
+
+  Cancelable<R> executeGentle<R>(ExecuteGentle<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
+    return _createCancelable<R>(execution: execution, priority: priority);
+  }
+
+  Cancelable<R> executeGentleWithPort<R, T>(
+    ExecuteGentleWithPort<R> execution, {
+    WorkPriority priority = WorkPriority.immediately,
+    required void Function(T value) onMessage,
+  }) {
+    return _createCancelable<R>(
+      execution: execution,
+      priority: priority,
+      onMessage: (message) => onMessage(message as T),
+    );
+  }
+
+  void _createWorkers() {
+    for (var i = 0; i < _isolatesCount; i++) {
+      _pool.add(Worker());
+    }
+  }
+
+  Future<void> _initializeWorkers() async {
+    await Future.wait(_pool.map((e) => e.initialize()));
+  }
+
+  Cancelable<R> _createCancelable<R>({
+    required Function execution,
+    WorkPriority priority = WorkPriority.immediately,
+    void Function(Object value)? onMessage,
+  }) {
+    if (_nextTaskId + 1 == _maxId) {
+      _nextTaskId = _minId;
+    }
+    final id = _nextTaskId.toString();
+    _nextTaskId++;
+    late final Task<R> task;
+    final completer = Completer<R>();
+    if (execution is Execute<R>) {
+      task = TaskRegular<R>(id: id, workPriority: priority, execution: execution, completer: completer);
+    } else if (execution is ExecuteWithPort<R>) {
+      task = TaskWithPort<R>(
+        id: id,
+        workPriority: priority,
+        execution: execution,
+        completer: completer,
+        onMessage: onMessage!,
+      );
+    } else if (execution is ExecuteGentle<R>) {
+      task = TaskGentle<R>(id: id, workPriority: priority, execution: execution, completer: completer);
+    } else if (execution is ExecuteGentleWithPort<R>) {
+      task = TaskGentleWithPort<R>(
+        id: id,
+        workPriority: priority,
+        execution: execution,
+        completer: completer,
+        onMessage: onMessage!,
+      );
+    }
+    _queue.add(task);
+    _schedule();
+    logTaskAdded(task.id);
+    return Cancelable(completer: task.completer, onCancel: () => _cancel(task));
+  }
+
+  Future<void> _ensureWorkersInitialized() async {
+    if (_pool.isEmpty) {
+      _createWorkers();
+      if (!_dynamicSpawning) {
+        await _initializeWorkers();
+        final poolSize = _pool.length;
+        final queueSize = _queue.length;
+        for (int i = 0; i <= min(poolSize, queueSize); i++) {
+          _schedule();
+        }
+      }
+    }
+    if (_pool.every((worker) => worker.taskId != null)) {
+      return;
+    }
+    if (_dynamicSpawning) {
+      final freeWorker = _pool.firstWhereOrNull(
+        (worker) => worker.taskId == null && !worker.initialized && !worker.initializing,
+      );
+      await freeWorker?.initialize();
+      _schedule();
+    }
+  }
+
+  void _schedule() {
+    final availableWorker = _pool.firstWhereOrNull((worker) => worker.taskId == null && worker.initialized);
+    if (availableWorker == null) {
+      _ensureWorkersInitialized();
+      return;
+    }
+    if (_queue.isEmpty) return;
+    final task = _queue.removeFirst();
+
+    availableWorker
+        .work(task)
+        .then(
+          (value) {
+            //could be completed already by cancel and it is normal.
+            //Assuming that worker finished with error and cleaned gracefully
+            task.complete(value, null, null);
+          },
+          onError: (error, st) {
+            task.complete(null, error, st);
+          },
+        )
+        .whenComplete(() {
+          if (_dynamicSpawning && _queue.isEmpty) availableWorker.kill();
+          _schedule();
+        });
+  }
+
+  @override
+  void _cancel(Task task) {
+    task.cancel();
+    _queue.remove(task);
+    final targetWorker = _pool.firstWhereOrNull((worker) => worker.taskId == task.id);
+    if (task is Gentle) {
+      targetWorker?.cancelGentle();
+    } else {
+      targetWorker?.kill();
+      if (!_dynamicSpawning) targetWorker?.initialize();
+    }
+    super._cancel(task);
+  }
+}