Fix: Retry when inserting records offline

Author: mugikhan

android/app/build.gradle

@@ -49,7 +49,7 @@ android {
         applicationId "co.powersync.demotodolist"
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
-        minSdkVersion 19
+        minSdkVersion 23
         targetSdkVersion flutter.targetSdkVersion
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName

android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.7.10'
+    ext.kotlin_version = '2.0.0'
     repositories {
         google()
         mavenCentral()

android/gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.5-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.1-bin.zip

lib/powersync.dart

@@ -37,10 +37,9 @@ class BackendConnector extends PowerSyncBackendConnector {
   /// Get a token to authenticate against the PowerSync instance.
   @override
   Future<PowerSyncCredentials?> fetchCredentials() async {
-
     final user = FirebaseAuth.instance.currentUser;
-    if(user == null) {
-    // Not logged in
+    if (user == null) {
+      // Not logged in
       return null;
     }
     final idToken = await user.getIdToken();
@@ -64,14 +63,16 @@ class BackendConnector extends PowerSyncBackendConnector {
       // userId and expiresAt are for debugging purposes only
       final expiresAt = parsedBody['expiresAt'] == null
           ? null
-          : DateTime.fromMillisecondsSinceEpoch(parsedBody['expiresAt']! * 1000);
+          : DateTime.fromMillisecondsSinceEpoch(
+              parsedBody['expiresAt']! * 1000);
       return PowerSyncCredentials(
           endpoint: parsedBody['powerSyncUrl'],
           token: parsedBody['token'],
           userId: parsedBody['userId'],
           expiresAt: expiresAt);
     } else {
       print('Request failed with status: ${response.statusCode}');
+      return null;
     }
   }
 
@@ -109,33 +110,44 @@ class BackendConnector extends PowerSyncBackendConnector {
 
         var row = Map<String, dynamic>.of(op.opData!);
         row['id'] = op.id;
-        Map<String, dynamic> data = {
-          "table": op.table,
-          "data": row
-        };
-
+        Map<String, dynamic> data = {"table": op.table, "data": row};
         if (op.op == UpdateType.put) {
           await upsert(data);
         } else if (op.op == UpdateType.patch) {
           await update(data);
         } else if (op.op == UpdateType.delete) {
+          data = {
+            "table": op.table,
+            "data": {"id": op.id}
+          };
           await delete(data);
         }
       }
 
       // All operations successful.
       await transaction.complete();
+    } on http.ClientException catch (e) {
+      // Error may be retryable - e.g. network error or temporary server error.
+      // Throwing an error here causes this call to be retried after a delay.
+      log.warning('Client exception', e);
+      rethrow;
     } catch (e) {
-      log.severe('Failed to update object $e');
-      transaction.complete();
+      /// Instead of blocking the queue with these errors,
+      /// discard the (rest of the) transaction.
+      ///
+      /// Note that these errors typically indicate a bug in the application.
+      /// If protecting against data loss is important, save the failing records
+      /// elsewhere instead of discarding, and/or notify the user.
+      log.severe('Data upload error - discarding $lastOp', e);
+      await transaction.complete();
     }
   }
 }
 
 /// Global reference to the database
 late final PowerSyncDatabase db;
 
-upsert (data) async {
+upsert(data) async {
   var url = Uri.parse("${AppConfig.backendUrl}/api/data");
 
   try {
@@ -154,10 +166,11 @@ upsert (data) async {
     }
   } catch (e) {
     log.severe('Exception occurred: $e');
+    rethrow;
   }
 }
 
-update (data) async {
+update(data) async {
   var url = Uri.parse("${AppConfig.backendUrl}/api/data");
 
   try {
@@ -176,10 +189,11 @@ update (data) async {
     }
   } catch (e) {
     log.severe('Exception occurred: $e');
+    rethrow;
   }
 }
 
-delete (data) async {
+delete(data) async {
   var url = Uri.parse("${AppConfig.backendUrl}/api/data");
 
   try {
@@ -198,6 +212,7 @@ delete (data) async {
     }
   } catch (e) {
     log.severe('Exception occurred: $e');
+    rethrow;
   }
 }
 
@@ -219,7 +234,11 @@ Future<String> getDatabasePath() async {
 
 Future<void> openDatabase() async {
   // Open the local database
-  db = PowerSyncDatabase(schema: schema, path: await getDatabasePath());
+  db = PowerSyncDatabase(
+    schema: schema,
+    path: await getDatabasePath(),
+    logger: attachedLogger,
+  );
   await db.initialize();
   BackendConnector? currentConnector;
 
@@ -235,9 +254,7 @@ Future<void> openDatabase() async {
     log.info('User not logged in, setting connection');
   }
 
-  FirebaseAuth.instance
-      .authStateChanges()
-      .listen((User? user) async {
+  FirebaseAuth.instance.authStateChanges().listen((User? user) async {
     if (user != null) {
       // Connect to PowerSync when the user is signed in
       currentConnector = BackendConnector(db);
@@ -252,5 +269,5 @@ Future<void> openDatabase() async {
 /// Explicit sign out - clear database and log out.
 Future<void> logout() async {
   await FirebaseAuth.instance.signOut();
-  await db.disconnectedAndClear();
+  await db.disconnectAndClear();
 }

lib/widgets/list_item.dart

@@ -17,13 +17,6 @@ class ListItemWidget extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    viewList() {
-      var navigator = Navigator.of(context);
-
-      navigator.push(
-          MaterialPageRoute(builder: (context) => TodoListPage(list: list)));
-    }
-
     final subtext =
         '${list.pendingCount} pending, ${list.completedCount} completed';
 
@@ -32,7 +25,10 @@ class ListItemWidget extends StatelessWidget {
         mainAxisSize: MainAxisSize.min,
         children: <Widget>[
           ListTile(
-              onTap: viewList,
+              onTap: () {
+                Navigator.of(context).push(MaterialPageRoute(
+                    builder: (context) => TodoListPage(list: list)));
+              },
               leading: const Icon(Icons.list),
               title: Text(list.name),
               subtitle: Text(subtext)),

lib/widgets/status_app_bar.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:powersync/powersync.dart';
 import '../powersync.dart';
@@ -39,22 +40,56 @@ class _StatusAppBarState extends State<StatusAppBar> {
 
   @override
   Widget build(BuildContext context) {
-    const connectedIcon = IconButton(
-      icon: Icon(Icons.wifi),
-      tooltip: 'Connected',
-      onPressed: null,
-    );
-    const disconnectedIcon = IconButton(
-      icon: Icon(Icons.wifi_off),
-      tooltip: 'Not connected',
-      onPressed: null,
-    );
+    final statusIcon = _getStatusIcon(_connectionState, context);
 
     return AppBar(
       title: Text(widget.title),
       actions: <Widget>[
-        _connectionState.connected ? connectedIcon : disconnectedIcon
+        statusIcon,
+        // Make some space for the "Debug" banner, so that the status
+        // icon isn't hidden
+        if (kDebugMode) _makeIcon('Debug mode', Icons.developer_mode, context),
       ],
     );
   }
 }
+
+Widget _makeIcon(String text, IconData icon, BuildContext context) {
+  return Tooltip(
+      message: text,
+      child: InkWell(
+          onTap: () {
+            ScaffoldMessenger.of(context)
+                .showSnackBar(SnackBar(content: Text('Status: $text')));
+          },
+          child:
+              SizedBox(width: 40, height: null, child: Icon(icon, size: 24))));
+}
+
+Widget _getStatusIcon(SyncStatus status, BuildContext context) {
+  if (status.anyError != null) {
+    // The error message is verbose, could be replaced with something
+    // more user-friendly
+    if (!status.connected) {
+      return _makeIcon(status.anyError!.toString(), Icons.cloud_off, context);
+    } else {
+      return _makeIcon(
+          status.anyError!.toString(), Icons.sync_problem, context);
+    }
+  } else if (status.connecting) {
+    return _makeIcon('Connecting', Icons.cloud_sync_outlined, context);
+  } else if (!status.connected) {
+    return _makeIcon('Not connected', Icons.cloud_off, context);
+  } else if (status.uploading && status.downloading) {
+    // The status changes often between downloading, uploading and both,
+    // so we use the same icon for all three
+    return _makeIcon(
+        'Uploading and downloading', Icons.cloud_sync_outlined, context);
+  } else if (status.uploading) {
+    return _makeIcon('Uploading', Icons.cloud_sync_outlined, context);
+  } else if (status.downloading) {
+    return _makeIcon('Downloading', Icons.cloud_sync_outlined, context);
+  } else {
+    return _makeIcon('Connected', Icons.cloud_queue, context);
+  }
+}

linux/flutter/generated_plugin_registrant.cc

@@ -6,10 +6,18 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <gtk/gtk_plugin.h>
+#include <powersync_flutter_libs/powersync_flutter_libs_plugin.h>
 #include <sqlite3_flutter_libs/sqlite3_flutter_libs_plugin.h>
 #include <url_launcher_linux/url_launcher_plugin.h>
 
 void fl_register_plugins(FlPluginRegistry* registry) {
+  g_autoptr(FlPluginRegistrar) gtk_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "GtkPlugin");
+  gtk_plugin_register_with_registrar(gtk_registrar);
+  g_autoptr(FlPluginRegistrar) powersync_flutter_libs_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "PowersyncFlutterLibsPlugin");
+  powersync_flutter_libs_plugin_register_with_registrar(powersync_flutter_libs_registrar);
   g_autoptr(FlPluginRegistrar) sqlite3_flutter_libs_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "Sqlite3FlutterLibsPlugin");
   sqlite3_flutter_libs_plugin_register_with_registrar(sqlite3_flutter_libs_registrar);

linux/flutter/generated_plugins.cmake

@@ -3,6 +3,8 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  gtk
+  powersync_flutter_libs
   sqlite3_flutter_libs
   url_launcher_linux
 )

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -9,8 +9,8 @@ import app_links
 import firebase_auth
 import firebase_core
 import path_provider_foundation
+import powersync_flutter_libs
 import shared_preferences_foundation
-import sign_in_with_apple
 import sqlite3_flutter_libs
 import url_launcher_macos
 
@@ -19,8 +19,8 @@ func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
   FLTFirebaseAuthPlugin.register(with: registry.registrar(forPlugin: "FLTFirebaseAuthPlugin"))
   FLTFirebaseCorePlugin.register(with: registry.registrar(forPlugin: "FLTFirebaseCorePlugin"))
   PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
+  PowersyncFlutterLibsPlugin.register(with: registry.registrar(forPlugin: "PowersyncFlutterLibsPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
-  SignInWithApplePlugin.register(with: registry.registrar(forPlugin: "SignInWithApplePlugin"))
   Sqlite3FlutterLibsPlugin.register(with: registry.registrar(forPlugin: "Sqlite3FlutterLibsPlugin"))
   UrlLauncherPlugin.register(with: registry.registrar(forPlugin: "UrlLauncherPlugin"))
 }