[Feature] Implement web sync locks (#119)

* implement sync locks

Author: stevensJourney

CHANGELOG.md

@@ -3,6 +3,34 @@
 All notable changes to this project will be documented in this file.
 See [Conventional Commits](https://conventionalcommits.org) for commit guidelines.
 
+## 2024-07-10
+
+### Changes
+
+---
+
+Packages with breaking changes:
+
+ - There are no breaking changes in this release.
+
+Packages with other changes:
+
+ - [`powersync` - `v1.3.0-alpha.9`](#powersync---v130-alpha9)
+ - [`powersync_attachments_helper` - `v0.3.0-alpha.4`](#powersync_attachments_helper---v030-alpha4)
+
+Packages with dependency updates only:
+
+> Packages listed below depend on other packages in this workspace that have had changes. Their versions have been incremented to bump the minimum dependency versions of the packages they depend upon in this project.
+
+ - `powersync_attachments_helper` - `v0.3.0-alpha.4`
+
+---
+
+#### `powersync` - `v1.3.0-alpha.9`
+
+ - Updated sqlite_async to use Navigator locks for limiting sync stream implementions in multiple tabs
+
+
 ## 2024-07-04
 
 ### Changes

demos/supabase-anonymous-auth/pubspec.lock

@@ -350,7 +350,7 @@ packages:
       path: "../../packages/powersync"
       relative: true
     source: path
-    version: "1.3.0-alpha.7"
+    version: "1.3.0-alpha.8"
   realtime_client:
     dependency: transitive
     description:
@@ -480,10 +480,10 @@ packages:
     dependency: "direct main"
     description:
       name: sqlite_async
-      sha256: "7c5a9bec86b6f5b7511b9ba30974fa7ea470aee2dc0d5b7021f6321a439a8d63"
+      sha256: "79e636c857ed43f6cd5e5be72b36967a29f785daa63ff5b078bd34f74f44cb54"
       url: "https://pub.dev"
     source: hosted
-    version: "0.8.0"
+    version: "0.8.1"
   stack_trace:
     dependency: transitive
     description:

demos/supabase-anonymous-auth/pubspec.yaml

@@ -11,12 +11,12 @@ dependencies:
   flutter:
     sdk: flutter
 
-  powersync: 1.3.0-alpha.8
+  powersync: 1.3.0-alpha.9
   path_provider: ^2.1.1
   supabase_flutter: ^2.0.2
   path: ^1.8.3
   logging: ^1.2.0
-  sqlite_async: ^0.8.0
+  sqlite_async: ^0.8.1
   universal_io: ^2.2.2
 
 dev_dependencies:

demos/supabase-edge-function-auth/pubspec.lock

@@ -350,7 +350,7 @@ packages:
       path: "../../packages/powersync"
       relative: true
     source: path
-    version: "1.3.0-alpha.7"
+    version: "1.3.0-alpha.8"
   realtime_client:
     dependency: transitive
     description:
@@ -480,10 +480,10 @@ packages:
     dependency: "direct main"
     description:
       name: sqlite_async
-      sha256: "7c5a9bec86b6f5b7511b9ba30974fa7ea470aee2dc0d5b7021f6321a439a8d63"
+      sha256: "79e636c857ed43f6cd5e5be72b36967a29f785daa63ff5b078bd34f74f44cb54"
       url: "https://pub.dev"
     source: hosted
-    version: "0.8.0"
+    version: "0.8.1"
   stack_trace:
     dependency: transitive
     description:

demos/supabase-edge-function-auth/pubspec.yaml

@@ -11,12 +11,12 @@ dependencies:
   flutter:
     sdk: flutter
 
-  powersync: 1.3.0-alpha.8
+  powersync: 1.3.0-alpha.9
   path_provider: ^2.1.1
   supabase_flutter: ^2.0.2
   path: ^1.8.3
   logging: ^1.2.0
-  sqlite_async: ^0.8.0
+  sqlite_async: ^0.8.1
   universal_io: ^2.2.2
 
 dev_dependencies:

demos/supabase-simple-chat/pubspec.lock

@@ -382,7 +382,7 @@ packages:
       path: "../../packages/powersync"
       relative: true
     source: path
-    version: "1.3.0-alpha.7"
+    version: "1.3.0-alpha.8"
   realtime_client:
     dependency: transitive
     description:
@@ -536,10 +536,10 @@ packages:
     dependency: transitive
     description:
       name: sqlite_async
-      sha256: "7c5a9bec86b6f5b7511b9ba30974fa7ea470aee2dc0d5b7021f6321a439a8d63"
+      sha256: "79e636c857ed43f6cd5e5be72b36967a29f785daa63ff5b078bd34f74f44cb54"
       url: "https://pub.dev"
     source: hosted
-    version: "0.8.0"
+    version: "0.8.1"
   stack_trace:
     dependency: transitive
     description:

demos/supabase-simple-chat/pubspec.yaml

@@ -37,7 +37,7 @@ dependencies:
 
   supabase_flutter: ^1.10.25
   timeago: ^3.6.0
-  powersync: 1.3.0-alpha.8
+  powersync: 1.3.0-alpha.9
   path_provider: ^2.1.1
   path: ^1.8.3
   logging: ^1.2.0

demos/supabase-todolist/pubspec.lock

@@ -454,14 +454,14 @@ packages:
       path: "../../packages/powersync"
       relative: true
     source: path
-    version: "1.3.0-alpha.7"
+    version: "1.3.0-alpha.8"
   powersync_attachments_helper:
     dependency: "direct main"
     description:
       path: "../../packages/powersync_attachments_helper"
       relative: true
     source: path
-    version: "0.3.0-alpha.2"
+    version: "0.3.0-alpha.3"
   realtime_client:
     dependency: transitive
     description:
@@ -591,10 +591,10 @@ packages:
     dependency: "direct main"
     description:
       name: sqlite_async
-      sha256: "7c5a9bec86b6f5b7511b9ba30974fa7ea470aee2dc0d5b7021f6321a439a8d63"
+      sha256: "79e636c857ed43f6cd5e5be72b36967a29f785daa63ff5b078bd34f74f44cb54"
       url: "https://pub.dev"
     source: hosted
-    version: "0.8.0"
+    version: "0.8.1"
   stack_trace:
     dependency: transitive
     description:

demos/supabase-todolist/pubspec.yaml

@@ -10,17 +10,17 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
-  powersync_attachments_helper: ^0.3.0-alpha.3
+  powersync_attachments_helper: ^0.3.0-alpha.4
 
-  powersync: 1.3.0-alpha.8
+  powersync: 1.3.0-alpha.9
   path_provider: ^2.1.1
   supabase_flutter: ^2.0.1
   path: ^1.8.3
   logging: ^1.2.0
   camera: ^0.10.5+7
   image: ^4.1.3
   universal_io: ^2.2.2
-  sqlite_async: ^0.8.0
+  sqlite_async: ^0.8.1
 
 dev_dependencies:
   flutter_test:

packages/powersync/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.3.0-alpha.9
+
+- Updated sqlite_async to use Navigator locks for limiting sync stream implementations in multiple tabs
+
 ## 1.3.0-alpha.8
 
 - **FIX**(powersync-attachements-helper): pubspec file (#29).

packages/powersync/lib/src/database/web/web_powersync_database.dart

@@ -134,17 +134,19 @@ class PowerSyncDatabaseImpl
 
     await isInitialized;
 
-    // TODO multitab support
+    // TODO better multitab support
     final storage = BucketStorage(database);
-
     final sync = StreamingSyncImplementation(
         adapter: storage,
         credentialsCallback: connector.getCredentialsCached,
         invalidCredentialsCallback: connector.fetchCredentials,
         uploadCrud: () => connector.uploadData(this),
         updateStream: updates,
         retryDelay: Duration(seconds: 3),
-        client: FetchClient(mode: RequestMode.cors));
+        client: FetchClient(mode: RequestMode.cors),
+        // Only allows 1 sync implementation to run at a time per database
+        // This should be global (across tabs) when using Navigator locks.
+        identifier: database.openFactory.path);
     sync.statusStream.listen((event) {
       setStatus(event);
     });

packages/powersync/lib/src/streaming_sync.dart

@@ -4,6 +4,7 @@ import 'package:http/http.dart' as http;
 import 'package:powersync/src/abort_controller.dart';
 import 'package:powersync/src/exceptions.dart';
 import 'package:powersync/src/log_internal.dart';
+import 'package:sqlite_async/mutex.dart';
 
 import 'bucket_storage.dart';
 import 'connector.dart';
@@ -37,14 +38,22 @@ class StreamingSyncImplementation {
 
   SyncStatus lastStatus = const SyncStatus();
 
+  final Mutex syncMutex, crudMutex;
+
   StreamingSyncImplementation(
       {required this.adapter,
       required this.credentialsCallback,
       this.invalidCredentialsCallback,
       required this.uploadCrud,
       required this.updateStream,
       required this.retryDelay,
-      required http.Client client}) {
+      required http.Client client,
+
+      /// A unique identifier for this streaming sync implementation
+      /// A good value is typically the DB file path which it will mutate when syncing.
+      String? identifier = "unknown"})
+      : syncMutex = Mutex(identifier: "sync-$identifier"),
+        crudMutex = Mutex(identifier: "crud-$identifier") {
     _client = client;
     statusStream = _statusStreamController.stream;
   }
@@ -65,8 +74,10 @@ class StreamingSyncImplementation {
           await invalidCredentialsCallback!();
           invalidCredentials = false;
         }
-        await streamingSyncIteration(abortController: abortController);
-        // Continue immediately
+        // Protect sync iterations with exclusivity (if a valid Mutex is provided)
+        await syncMutex.lock(
+            () => streamingSyncIteration(abortController: abortController),
+            timeout: retryDelay);
       } catch (e, stacktrace) {
         final message = _syncErrorMessage(e);
         isolateLogger.warning('Sync error: $message', e, stacktrace);
@@ -110,21 +121,23 @@ class StreamingSyncImplementation {
   }
 
   Future<bool> uploadCrudBatch() async {
-    if ((await adapter.hasCrud())) {
-      _updateStatus(uploading: true);
-      await uploadCrud();
-      return false;
-    } else {
-      // This isolate is the only one triggering
-      final updated = await adapter.updateLocalTarget(() async {
-        return getWriteCheckpoint();
-      });
-      if (updated) {
-        _localPingController.add(null);
-      }
+    return crudMutex.lock(() async {
+      if ((await adapter.hasCrud())) {
+        _updateStatus(uploading: true);
+        await uploadCrud();
+        return false;
+      } else {
+        // This isolate is the only one triggering
+        final updated = await adapter.updateLocalTarget(() async {
+          return getWriteCheckpoint();
+        });
+        if (updated) {
+          _localPingController.add(null);
+        }
 
-      return true;
-    }
+        return true;
+      }
+    }, timeout: retryDelay);
   }
 
   Future<String> getWriteCheckpoint() async {

packages/powersync/pubspec.yaml

@@ -1,5 +1,5 @@
 name: powersync
-version: 1.3.0-alpha.8
+version: 1.3.0-alpha.9
 homepage: https://powersync.com
 repository: https://github.com/powersync-ja/powersync.dart
 description: PowerSync Flutter SDK - keep PostgreSQL databases in sync with on-device SQLite databases.
@@ -10,7 +10,8 @@ dependencies:
   flutter:
     sdk: flutter
 
-  sqlite_async: ^0.8.0
+  sqlite_async: ^0.8.1
+
   universal_io: ^2.0.0
   sqlite3_flutter_libs: ^0.5.15
   meta: ^1.0.0

packages/powersync_attachments_helper/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.3.0-alpha.4
+
+ - Update a dependency to the latest release.
+
 ## 0.3.0-alpha.3
 
  - Update a dependency to the latest release.

packages/powersync_attachments_helper/pubspec.yaml

@@ -1,6 +1,6 @@
 name: powersync_attachments_helper
 description: A helper library for handling attachments when using PowerSync.
-version: 0.3.0-alpha.3
+version: 0.3.0-alpha.4
 repository: https://github.com/powersync-ja/powersync.dart
 homepage: https://www.powersync.com/
 environment:
@@ -10,7 +10,7 @@ dependencies:
   flutter:
     sdk: flutter
 
-  powersync: 1.3.0-alpha.8
+  powersync: 1.3.0-alpha.9
   logging: ^1.2.0
   sqlite3: "^2.4.4"
   path_provider: ^2.0.13