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Merged
merged 2 commits into from
Jun 3, 2025
Merged

Shared worker: Release mutex when tab closes #98

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9486ae1
Shared worker: Release mutex when tab closes
simolus3 Jun 3, 2025
cfdb89c
Actually we want to compile tests too
simolus3 Jun 3, 2025
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7 changes: 7 additions & 0 deletions packages/sqlite_async/build.yaml
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@@ -0,0 +1,7 @@
targets:
$default:
builders:
build_web_compilers:entrypoint:
options:
# Workers can't be compiled with dartdevc, so use dart2js for the example
compiler: dart2js
29 changes: 29 additions & 0 deletions packages/sqlite_async/example/web/index.html
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<!DOCTYPE html>

<html>
<head>
<meta charset="utf-8">
<title>sqlite_async web demo</title>
<script defer src="main.dart.js"></script>
</head>

<body>

<h1>sqlite_async demo</h1>

<main>
This page is used to test the sqlite_async package on the web.
Use the console to open and interact with databases.

<pre>
<code>
const db = await open('test.db');
const lock = await write_lock(db);
release_lock(lock);
</code>
</pre>
</main>


</body>
</html>
41 changes: 41 additions & 0 deletions packages/sqlite_async/example/web/main.dart
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import 'dart:async';
import 'dart:js_interop';
import 'dart:js_interop_unsafe';

import 'package:sqlite_async/sqlite_async.dart';

void main() {
globalContext['open'] = (String path) {
return Future(() async {
final db = SqliteDatabase(
path: path,
options: SqliteOptions(
webSqliteOptions: WebSqliteOptions(
wasmUri:
'https://cdn.jsdelivr.net/npm/@powersync/dart-wasm-bundles@latest/dist/sqlite3.wasm',
workerUri: 'worker.dart.js',
),
),
);
await db.initialize();
return db.toJSBox;
}).toJS;
}.toJS;

globalContext['write_lock'] = (JSBoxedDartObject db) {
final hasLock = Completer<void>();
final completer = Completer<void>();

(db.toDart as SqliteDatabase).writeLock((_) async {
print('has write lock!');
hasLock.complete();
await completer.future;
});

return hasLock.future.then((_) => completer.toJSBox).toJS;
}.toJS;

globalContext['release_lock'] = (JSBoxedDartObject db) {
(db.toDart as Completer<void>).complete();
}.toJS;
}
6 changes: 6 additions & 0 deletions packages/sqlite_async/example/web/worker.dart
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import 'package:sqlite_async/sqlite3_web.dart';
import 'package:sqlite_async/sqlite3_web_worker.dart';

void main() {
WebSqlite.workerEntrypoint(controller: AsyncSqliteController());
}
26 changes: 26 additions & 0 deletions packages/sqlite_async/lib/src/web/worker/worker_utils.dart
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Expand Up @@ -56,9 +56,27 @@ class AsyncSqliteDatabase extends WorkerDatabase {
// these requests for shared workers, so we can assume each database is only
// opened once and we don't need web locks here.
final mutex = ReadWriteMutex();
final Map<ClientConnection, _ConnectionState> _state = {};

AsyncSqliteDatabase({required this.database});

_ConnectionState _findState(ClientConnection connection) {
return _state.putIfAbsent(connection, _ConnectionState.new);
}

void _markHoldsMutex(ClientConnection connection) {
final state = _findState(connection);
state.holdsMutex = true;
if (!state.hasOnCloseListener) {
state.hasOnCloseListener = true;
connection.closed.then((_) {
if (state.holdsMutex) {
mutex.release();
}
});
}
}

@override
Future<JSAny?> handleCustomRequest(
ClientConnection connection, JSAny? request) async {
Expand All @@ -67,9 +85,12 @@ class AsyncSqliteDatabase extends WorkerDatabase {
switch (message.kind) {
case CustomDatabaseMessageKind.requestSharedLock:
await mutex.acquireRead();
_markHoldsMutex(connection);
case CustomDatabaseMessageKind.requestExclusiveLock:
await mutex.acquireWrite();
_markHoldsMutex(connection);
case CustomDatabaseMessageKind.releaseLock:
_findState(connection).holdsMutex = false;
mutex.release();
case CustomDatabaseMessageKind.lockObtained:
throw UnsupportedError('This is a response, not a request');
Expand Down Expand Up @@ -123,3 +144,8 @@ class AsyncSqliteDatabase extends WorkerDatabase {
return resultSetMap;
}
}

final class _ConnectionState {
bool hasOnCloseListener = false;
bool holdsMutex = false;
}