Measure latency.

Author: rkistner

demos/benchmarks/lib/app_config_template.dart

@@ -2,5 +2,6 @@
 // Edit lib/app_config.dart and enter your PowerSync project details.
 class AppConfig {
   static const String powersyncUrl = 'http://localhost:8080';
+  static const String backendUrl = 'http://localhost:6060';
   static const String token = '';
 }

demos/benchmarks/lib/models/benchmark_item.dart

@@ -9,21 +9,24 @@ class BenchmarkItem {
   final String description;
 
   final DateTime clientCreatedAt;
+  final DateTime? clientReceivedAt;
 
   final DateTime? serverCreatedAt;
 
   BenchmarkItem(
       {required this.id,
       required this.description,
       required this.clientCreatedAt,
+      this.clientReceivedAt,
       this.serverCreatedAt});
 
   factory BenchmarkItem.fromRow(sqlite.Row row) {
     return BenchmarkItem(
         id: row['id'],
         description: row['description'] ?? '',
         clientCreatedAt: DateTime.parse(row['client_created_at']),
-        serverCreatedAt: DateTime.tryParse(row['client_created_at'] ?? ''));
+        clientReceivedAt: DateTime.tryParse(row['client_received_at'] ?? ''),
+        serverCreatedAt: DateTime.tryParse(row['server_created_at'] ?? ''));
   }
 
   static Stream<List<BenchmarkItem>> watchItems() {
@@ -35,26 +38,50 @@ class BenchmarkItem {
     });
   }
 
+  static updateItemBenchmarks() async {
+    await for (var _ in db.onChange(['benchmark_items'],
+        throttle: const Duration(milliseconds: 1))) {
+      await db.execute(
+          '''UPDATE benchmark_items SET client_received_at = datetime('now', 'subsecond') || 'Z' WHERE client_received_at IS NULL AND server_created_at IS NOT NULL''');
+    }
+  }
+
   /// Create a new list
   static Future<BenchmarkItem> create(String description) async {
     final results = await db.execute('''
       INSERT INTO
         benchmark_items(id, description, client_created_at)
-        VALUES(uuid(), ?, datetime())
+        VALUES(uuid(), ?, datetime('now', 'subsecond') || 'Z')
       RETURNING *
       ''', [description]);
     return BenchmarkItem.fromRow(results.first);
   }
 
-  /// Delete this item.
-  Future<void> delete() async {
-    await db.execute('DELETE FROM benchmark_items WHERE id = ?', [id]);
-  }
-
   /// Find list item.
   static Future<BenchmarkItem> find(id) async {
     final results =
         await db.get('SELECT * FROM benchmark_items WHERE id = ?', [id]);
     return BenchmarkItem.fromRow(results);
   }
+
+  /// Delete this item.
+  Future<void> delete() async {
+    await db.execute('DELETE FROM benchmark_items WHERE id = ?', [id]);
+  }
+
+  Duration? get latency {
+    if (clientReceivedAt == null) {
+      return null;
+    } else {
+      return clientReceivedAt!.difference(clientCreatedAt);
+    }
+  }
+
+  Duration? get uploadLatency {
+    if (serverCreatedAt == null) {
+      return null;
+    } else {
+      return serverCreatedAt!.difference(clientCreatedAt);
+    }
+  }
 }

demos/benchmarks/lib/models/schema.dart

@@ -4,6 +4,7 @@ Schema schema = const Schema(([
   Table('benchmark_items', [
     Column.text('description'),
     Column.text('client_created_at'),
+    Column.text('client_received_at'),
     Column.text('server_created_at'),
   ]),
 ]));

demos/benchmarks/lib/powersync.dart

@@ -1,9 +1,15 @@
 // This file performs setup of the PowerSync database
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:http/http.dart' as http;
+
 import 'package:flutter/foundation.dart';
 import 'package:logging/logging.dart';
 import 'package:path/path.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:powersync/powersync.dart';
+import 'package:powersync_benchmarks/models/benchmark_item.dart';
 
 import './app_config.dart';
 import './models/schema.dart';
@@ -12,7 +18,9 @@ final log = Logger('powersync-supabase');
 
 /// Use Supabase for authentication and data upload.
 class BackendConnector extends PowerSyncBackendConnector {
-  BackendConnector();
+  http.Client client;
+
+  BackendConnector() : client = http.Client();
 
   @override
   Future<PowerSyncCredentials?> fetchCredentials() async {
@@ -31,7 +39,36 @@ class BackendConnector extends PowerSyncBackendConnector {
       return;
     }
 
-    // TODO: Implement
+    var uri = Uri.parse('${AppConfig.backendUrl}/api/data');
+
+    var body = jsonEncode({
+      'batch': transaction.crud.map((op) {
+        if (op.op == UpdateType.put) {
+          return {
+            'op': 'PUT',
+            'table': op.table,
+            'id': op.id,
+            'data': op.opData
+          };
+        } else if (op.op == UpdateType.patch) {
+          return {
+            'op': 'PATCH',
+            'table': op.table,
+            'id': op.id,
+            'data': op.opData
+          };
+        } else if (op.op == UpdateType.delete) {
+          return {'op': 'DELETE', 'table': op.table, 'id': op.id};
+        }
+      }).toList()
+    });
+    var response = await client.post(uri,
+        headers: {'Content-Type': 'application/json'}, body: body);
+    if (response.statusCode < 200 || response.statusCode >= 300) {
+      throw http.ClientException(
+          'Data upload failed with ${response.statusCode} ${response.body}');
+    }
+
     await transaction.complete();
   }
 }
@@ -55,7 +92,11 @@ Future<void> openDatabase() async {
       schema: schema, path: await getDatabasePath(), logger: attachedLogger);
   await db.initialize();
 
+  BenchmarkItem.updateItemBenchmarks();
+
   var currentConnector = BackendConnector();
 
-  db.connect(connector: currentConnector);
+  db.connect(
+      connector: currentConnector,
+      crudThrottleTime: const Duration(milliseconds: 1));
 }

demos/benchmarks/lib/widgets/benchmark_item_widget.dart

@@ -15,12 +15,24 @@ class ListItemWidget extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    String latency =
+        item.latency != null ? '${item.latency!.inMilliseconds}ms' : '';
+
+    String uploadLatency = item.uploadLatency != null
+        ? '${item.uploadLatency!.inMilliseconds}ms'
+        : '';
+
+    String subtitle =
+        '$latency / $uploadLatency / ${item.serverCreatedAt?.toIso8601String() ?? ''}';
     return Card(
       child: Column(
         mainAxisSize: MainAxisSize.min,
         children: <Widget>[
           ListTile(
-              leading: const Icon(Icons.list), title: Text(item.description)),
+            leading: const Icon(Icons.list),
+            title: Text(item.description),
+            subtitle: Text(subtitle),
+          ),
           Row(
             mainAxisAlignment: MainAxisAlignment.end,
             children: <Widget>[

demos/benchmarks/pubspec.lock

@@ -124,7 +124,7 @@ packages:
     source: sdk
     version: "0.0.0"
   http:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: http
       sha256: b9c29a161230ee03d3ccf545097fccd9b87a5264228c5d348202e0f0c28f9010

demos/benchmarks/pubspec.yaml

@@ -16,6 +16,7 @@ dependencies:
   logging: ^1.2.0
   universal_io: ^2.2.2
   sqlite_async: ^0.9.0
+  http: ^1.2.2
 
 dev_dependencies:
   flutter_test: