fix: Add reconnect check in case of timeouts on the db side

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/private/DB/Connection.php

@@ -41,6 +41,7 @@
 use Doctrine\DBAL\Connections\PrimaryReadReplicaConnection;
 use Doctrine\DBAL\Driver;
 use Doctrine\DBAL\Exception;
+use Doctrine\DBAL\Exception\ConnectionLost;
 use Doctrine\DBAL\Platforms\MySQLPlatform;
 use Doctrine\DBAL\Platforms\OraclePlatform;
 use Doctrine\DBAL\Platforms\SqlitePlatform;
@@ -78,6 +79,7 @@ class Connection extends PrimaryReadReplicaConnection {
 
 	/** @var DbDataCollector|null */
 	protected $dbDataCollector = null;
+	private array $lastConnectionCheck = [];
 
 	protected ?float $transactionActiveSince = null;
 
@@ -127,10 +129,13 @@ public function __construct(
 	public function connect($connectionName = null) {
 		try {
 			if ($this->_conn) {
+				$this->reconnectIfNeeded($connectionName);
 				/** @psalm-suppress InternalMethod */
 				return parent::connect();
 			}
 
+			$this->lastConnectionCheck[$connectionName] = time();
+
 			// Only trigger the event logger for the initial connect call
 			$eventLogger = \OC::$server->get(IEventLogger::class);
 			$eventLogger->start('connect:db', 'db connection opened');
@@ -679,4 +684,18 @@ public function rollBack() {
 		}
 		return $result;
 	}
+
+	private function reconnectIfNeeded(string $connectionName): void {
+		if ($this->lastConnectionCheck[$connectionName] + 30 >= time() || $this->isTransactionActive()) {
+			return;
+		}
+
+		try {
+			$this->_conn->query($this->getDriver()->getDatabasePlatform()->getDummySelectSQL());
+			$this->lastConnectionCheck[$connectionName] = time();
+		} catch (ConnectionLost|\Exception $e) {
+			$this->logger->warning('Exception during connectivity check, closing and reconnecting', ['exception' => $e]);
+			$this->close();
+		}
+	}
 }