Use WAL and durable connection defaults for SQLite

.env

@@ -28,6 +28,8 @@ DATABASE_DRIVER=mysql # or postgresql, or sqlite
 # For a PostgreSQL database, use: "postgresql://db_user:db_password@127.0.0.1:5432/db_name?serverVersion=11&charset=UTF-8"
 # For an SQLite database, use: "sqlite:///%kernel.project_dir%/var/data.db" (without the quotes so Symfony can resolve it if it's an absolute path)
 DATABASE_URL="mysql://davis:davis@127.0.0.1:3306/davis?serverVersion=10.9.3-MariaDB&charset=utf8mb4"
+# SQLite only. Use DELETE when the database cannot reside on a local filesystem.
+SQLITE_JOURNAL_MODE=WAL
 ###< doctrine/doctrine-bundle ###
 
 ###> symfony/mailer ###

README.md

@@ -118,6 +118,10 @@ DATABASE_DRIVER=mysql # or postgresql, or sqlite
 DATABASE_URL=mysql://db_user:db_pass@host:3306/db_name?serverVersion=10.9.3-MariaDB&charset=utf8mb4
 ```
 
+SQLite databases use WAL journaling, full synchronous writes, and a 60-second busy timeout by default. WAL requires the database and its auxiliary files to reside on a local filesystem. Set `SQLITE_JOURNAL_MODE=DELETE` when WAL is unavailable.
+
+Keep SQLite patched: SQLite reports a rare multi-connection [WAL-reset bug](https://www.sqlite.org/wal.html#the_wal_reset_bug) as likely present from 3.7.0 through 3.51.2, with fixes in 3.51.3 and the documented backports. The `-wal` file is part of a live database's state, so use SQLite's backup API or stop Davis and checkpoint before copying the database file.
+
 **b. The admin password for the backend**
 
 ```shell

config/services.yaml

@@ -5,6 +5,7 @@
 # https://symfony.com/doc/current/best_practices/configuration.html#application-related-configuration
 parameters:
     default_database_driver: "mysql"
+    default_sqlite_journal_mode: "WAL"
     default_admin_auth_bypass: "false"
     timezone: '%env(APP_TIMEZONE)%'
     public_calendars_enabled: '%env(default:default_public_calendars_enabled:bool:PUBLIC_CALENDARS_ENABLED)%'
@@ -30,6 +31,13 @@ services:
         arguments:
             $authRealm: "%env(AUTH_REALM)%"
 
+    App\Doctrine\SQLiteConnectionMiddleware:
+        autoconfigure: false
+        arguments:
+            $journalMode: "%env(default:default_sqlite_journal_mode:SQLITE_JOURNAL_MODE)%"
+        tags:
+            - { name: doctrine.middleware, priority: 100 }
+
     App\Services\IMAPAuth:
         arguments:
             $IMAPAuthUrl: "%env(IMAP_AUTH_URL)%"

src/Doctrine/SQLiteConnectionMiddleware.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Doctrine;
+
+use Doctrine\DBAL\Driver;
+use Doctrine\DBAL\Driver\Connection;
+use Doctrine\DBAL\Driver\Middleware;
+use Doctrine\DBAL\Driver\Middleware\AbstractDriverMiddleware;
+use Doctrine\DBAL\Platforms\SqlitePlatform;
+
+final class SQLiteConnectionMiddleware implements Middleware
+{
+    private string $journalMode;
+
+    public function __construct(string $journalMode)
+    {
+        $journalMode = strtoupper($journalMode);
+        if (!in_array($journalMode, ['WAL', 'DELETE'], true)) {
+            throw new \InvalidArgumentException('SQLITE_JOURNAL_MODE must be WAL or DELETE.');
+        }
+
+        $this->journalMode = $journalMode;
+    }
+
+    public function wrap(Driver $driver): Driver
+    {
+        if (!$driver->getDatabasePlatform() instanceof SqlitePlatform) {
+            return $driver;
+        }
+
+        return new class($driver, $this->journalMode) extends AbstractDriverMiddleware {
+            public function __construct(Driver $driver, private readonly string $journalMode)
+            {
+                parent::__construct($driver);
+            }
+
+            public function connect(
+                #[\SensitiveParameter]
+                array $params,
+            ): Connection {
+                $connection = parent::connect($params);
+
+                $connection->exec('PRAGMA busy_timeout=60000');
+
+                if (!($params['memory'] ?? false)) {
+                    $journalMode = $connection->query('PRAGMA journal_mode='.$this->journalMode)->fetchOne();
+                    if (strtoupper((string) $journalMode) !== $this->journalMode) {
+                        throw new \RuntimeException(sprintf('SQLite could not enable %s journal mode; check filesystem support and database permissions.', $this->journalMode));
+                    }
+                }
+
+                $connection->exec('PRAGMA synchronous=FULL');
+
+                return $connection;
+            }
+        };
+    }
+}

tests/Functional/SQLiteConnectionTest.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace App\Tests\Functional;
+
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+
+class SQLiteConnectionTest extends KernelTestCase
+{
+    public function testServerDefaults(): void
+    {
+        self::bootKernel();
+
+        $connection = self::getContainer()->get(EntityManagerInterface::class)->getConnection();
+        if ('sqlite' !== $connection->getDatabasePlatform()->getName()) {
+            self::markTestSkipped('SQLite-specific connection defaults.');
+        }
+
+        self::assertSame('wal', $connection->fetchOne('PRAGMA journal_mode'));
+        self::assertSame(2, (int) $connection->fetchOne('PRAGMA synchronous'));
+        self::assertSame(60000, (int) $connection->fetchOne('PRAGMA busy_timeout'));
+    }
+}