feat(android) Check server is reachable before starting background backup

mobile/android/app/src/main/kotlin/com/example/mobile/BackgroundServicePlugin.kt

@@ -52,6 +52,7 @@ class BackgroundServicePlugin : FlutterPlugin, MethodChannel.MethodCallHandler {
                         .putBoolean(ContentObserverWorker.SHARED_PREF_SERVICE_ENABLED, true)
                         .putLong(BackupWorker.SHARED_PREF_CALLBACK_KEY, args.get(0) as Long)
                         .putString(BackupWorker.SHARED_PREF_NOTIFICATION_TITLE, args.get(1) as String)
+                        .putString(BackupWorker.SHARED_PREF_SERVER_URL, args.get(3) as String)
                         .apply()
                 ContentObserverWorker.enable(ctx, immediate = args.get(2) as Boolean)
                 result.success(true)

mobile/android/app/src/main/kotlin/com/example/mobile/BackupWorker.kt

@@ -11,8 +11,8 @@ import android.os.PowerManager
 import android.os.SystemClock
 import android.util.Log
 import androidx.annotation.RequiresApi
+import androidx.concurrent.futures.CallbackToFutureAdapter
 import androidx.core.app.NotificationCompat
-import androidx.concurrent.futures.ResolvableFuture
 import androidx.work.BackoffPolicy
 import androidx.work.Constraints
 import androidx.work.ForegroundInfo
@@ -30,6 +30,16 @@ import io.flutter.embedding.engine.loader.FlutterLoader
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
 import io.flutter.view.FlutterCallbackInformation
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import kotlinx.coroutines.withTimeoutOrNull
+import java.io.IOException
+import java.net.HttpURLConnection
+import java.net.InetAddress
+import java.net.URL
 import java.util.concurrent.TimeUnit
 
 /**
@@ -42,7 +52,6 @@ import java.util.concurrent.TimeUnit
  */
 class BackupWorker(ctx: Context, params: WorkerParameters) : ListenableWorker(ctx, params), MethodChannel.MethodCallHandler {
 
-    private val resolvableFuture = ResolvableFuture.create<Result>()
     private var engine: FlutterEngine? = null
     private lateinit var backgroundChannel: MethodChannel
     private val notificationManager = ctx.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
@@ -52,35 +61,80 @@ class BackupWorker(ctx: Context, params: WorkerParameters) : ListenableWorker(ct
     private var notificationDetailBuilder: NotificationCompat.Builder? = null
     private var fgFuture: ListenableFuture<Void>? = null
 
-    override fun startWork(): ListenableFuture<ListenableWorker.Result> {
+    private val job = Job()
+    private lateinit var completer: CallbackToFutureAdapter.Completer<Result>
+    private val resolvableFuture = CallbackToFutureAdapter.getFuture { completer ->
+        this.completer = completer
+        null
+    }
+
+    init {
+        resolvableFuture.addListener(
+            Runnable {
+                if (resolvableFuture.isCancelled) {
+                    job.cancel()
+                }
+            },
+            taskExecutor.serialTaskExecutor
+        )
+    }
 
+    override fun startWork(): ListenableFuture<ListenableWorker.Result> {
         Log.d(TAG, "startWork")
 
         val ctx = applicationContext
+        val prefs = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE)
 
-        if (!flutterLoader.initialized()) {
-            flutterLoader.startInitialization(ctx)
-        }
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-            // Create a Notification channel if necessary
-            createChannel()
-        }
-        if (isIgnoringBatteryOptimizations) {
-            // normal background services can only up to 10 minutes
-            // foreground services are allowed to run indefinitely
-            // requires battery optimizations to be disabled (either manually by the user
-            // or by the system learning that immich is important to the user)
-            val title = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE)
-                .getString(SHARED_PREF_NOTIFICATION_TITLE, NOTIFICATION_DEFAULT_TITLE)!!
-            showInfo(getInfoBuilder(title, indeterminate=true).build())
-        }
-        engine = FlutterEngine(ctx)
+        prefs.getString(SHARED_PREF_SERVER_URL, null)
+            ?.takeIf { it.isNotEmpty() }
+            ?.let { serverUrl -> doCoroutineWork(serverUrl) }
+            ?: doWork()
+        return resolvableFuture
+    }
 
-        flutterLoader.ensureInitializationCompleteAsync(ctx, null, Handler(Looper.getMainLooper())) {
-            runDart()
+    /**
+     * This function is used to check if server URL is reachable before starting the backup work.
+     * Check must be done in a background to avoid blocking the main thread.
+     */
+    private fun doCoroutineWork(serverUrl : String) {
+        CoroutineScope(Dispatchers.Default + job).launch {
+            val isReachable = isUrlReachableHttp(serverUrl)
+            withContext(Dispatchers.Main) {
+                if (isReachable) {
+                    doWork()
+                } else {
+                    // Fail when the URL is not reachable
+                    completer.set(Result.failure())
+                }
+            }
         }
+    }
 
-        return resolvableFuture
+    private fun doWork() {
+      Log.d(TAG, "doWork")
+      val ctx = applicationContext
+
+      if (!flutterLoader.initialized()) {
+        flutterLoader.startInitialization(ctx)
+      }
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+        // Create a Notification channel if necessary
+        createChannel()
+      }
+      if (isIgnoringBatteryOptimizations) {
+        // normal background services can only up to 10 minutes
+        // foreground services are allowed to run indefinitely
+        // requires battery optimizations to be disabled (either manually by the user
+        // or by the system learning that immich is important to the user)
+        val title = ctx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE)
+          .getString(SHARED_PREF_NOTIFICATION_TITLE, NOTIFICATION_DEFAULT_TITLE)!!
+        showInfo(getInfoBuilder(title, indeterminate=true).build())
+      }
+      engine = FlutterEngine(ctx)
+
+      flutterLoader.ensureInitializationCompleteAsync(ctx, null, Handler(Looper.getMainLooper())) {
+        runDart()
+      }
     }
 
     /**
@@ -139,7 +193,7 @@ class BackupWorker(ctx: Context, params: WorkerParameters) : ListenableWorker(ct
         engine = null
         if (result != null) {
             Log.d(TAG, "stopEngine result=${result}")
-            resolvableFuture.set(result)
+            this.completer.set(result)
         }
         waitOnSetForegroundAsync()
     }
@@ -270,6 +324,7 @@ class BackupWorker(ctx: Context, params: WorkerParameters) : ListenableWorker(ct
         const val SHARED_PREF_CALLBACK_KEY = "callbackDispatcherHandle"
         const val SHARED_PREF_NOTIFICATION_TITLE = "notificationTitle"
         const val SHARED_PREF_LAST_CHANGE = "lastChange"
+        const val SHARED_PREF_SERVER_URL = "serverUrl"
 
         private const val TASK_NAME_BACKUP = "immich/BackupWorker"
         private const val NOTIFICATION_CHANNEL_ID = "immich/backgroundService"
@@ -360,3 +415,26 @@ class BackupWorker(ctx: Context, params: WorkerParameters) : ListenableWorker(ct
 }
 
 private const val TAG = "BackupWorker"
+
+/**
+ * Check if the given URL is reachable via HTTP
+ */
+suspend fun isUrlReachableHttp(url: String, timeoutMillis: Long = 5000L): Boolean {
+    return withTimeoutOrNull(timeoutMillis) {
+        var httpURLConnection: HttpURLConnection? = null
+        try {
+            httpURLConnection = (URL(url).openConnection() as HttpURLConnection).apply {
+                requestMethod = "HEAD"
+                connectTimeout = timeoutMillis.toInt()
+                readTimeout = timeoutMillis.toInt()
+            }
+            httpURLConnection.connect()
+            httpURLConnection.responseCode == HttpURLConnection.HTTP_OK
+        } catch (e: Exception) {
+            Log.e(TAG, "Failed to reach server URL: $e")
+            false
+        } finally {
+            httpURLConnection?.disconnect()
+        }
+    } == true
+}

mobile/ios/Runner/BackgroundSync/BackgroundServicePlugin.swift

@@ -171,9 +171,9 @@ class BackgroundServicePlugin: NSObject, FlutterPlugin {
             return
         }
 
-        // Requires 3 arguments in the array
-        guard args.count == 3 else {
-            print("Requires 3 arguments and received \(args.count)")
+        // Requires 3 or more arguments in the array
+        guard args.count >= 3 else {
+            print("Requires 3 or more arguments and received \(args.count)")
             result(FlutterMethodNotImplemented)
             return
         }

mobile/lib/modules/backup/background_service/background.service.dart

@@ -20,6 +20,7 @@ import 'package:immich_mobile/shared/models/store.dart';
 import 'package:immich_mobile/shared/services/api.service.dart';
 import 'package:immich_mobile/utils/backup_progress.dart';
 import 'package:immich_mobile/utils/diff.dart';
+import 'package:immich_mobile/utils/url_helper.dart';
 import 'package:isar/isar.dart';
 import 'package:path_provider_ios/path_provider_ios.dart';
 import 'package:photo_manager/photo_manager.dart';
@@ -68,8 +69,10 @@ class BackgroundService {
       final callback = PluginUtilities.getCallbackHandle(_nativeEntry)!;
       final String title =
           "backup_background_service_default_notification".tr();
-      final bool ok = await _foregroundChannel
-          .invokeMethod('enable', [callback.toRawHandle(), title, immediate]);
+      final bool ok = await _foregroundChannel.invokeMethod(
+        'enable',
+        [callback.toRawHandle(), title, immediate, getServerUrl()],
+      );
       return ok;
     } catch (error) {
       return false;