69 lines
1.9 KiB
Dart
69 lines
1.9 KiB
Dart
import 'dart:async';
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import 'package:pool/pool.dart';
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import 'package:postgres/postgres.dart';
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/// Connects to a PostgreSQL database, whether synchronously or asynchronously.
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typedef FutureOr<PostgreSQLConnection> PostgreSQLConnector();
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/// Pools connections to a PostgreSQL database.
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class PostgreSQLConnectionPool {
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final List<PostgreSQLConnection> _connections = [];
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final List<int> _opened = [];
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int _index = 0;
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Pool _pool;
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/// The maximum number of concurrent connections to the database.
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///
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/// Default: `5`
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final int concurrency;
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/// An optional timeout for pooled connections to execute.
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final Duration timeout;
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/// A function that connects this pool to the database, on-demand.
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final PostgreSQLConnector connector;
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PostgreSQLConnectionPool(this.connector,
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{this.concurrency: 5, this.timeout}) {
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_pool = new Pool(concurrency, timeout: timeout);
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}
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Future<PostgreSQLConnection> _connect() async {
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if (_connections.isEmpty) {
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for (int i = 0; i < concurrency; i++) {
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_connections.add(await connector());
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}
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}
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var connection = _connections[_index++];
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if (_index >= _connections.length) _index = 0;
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if (!_opened.contains(connection.hashCode)) {
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await connection.open();
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_opened.add(connection.hashCode);
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}
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return connection;
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}
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Future close() => Future.wait(_connections.map((c) => c.close()));
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/// Connects to the database, and then executes the [callback].
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///
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/// Returns the result of [callback].
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Future<T> run<T>(FutureOr<T> callback(PostgreSQLConnection connection)) {
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return _pool.request().then((resx) {
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return _connect().then((connection) {
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return new Future<T>.sync(() => callback(connection))
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.whenComplete(() async {
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if (connection.isClosed) {
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_connections
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..remove(connection)
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..add(await connector());
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}
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resx.release();
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});
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});
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});
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}
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}
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