feat: Add logging for transaction time

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

lib/private/DB/Connection.php

@@ -81,6 +81,8 @@ class Connection extends PrimaryReadReplicaConnection {
 
 	protected $tableDirtyWrites = [];
 
+	protected ?float $transactionActiveSince = null;
+
 	/**
 	 * Initializes a new instance of the Connection class.
 	 *
@@ -333,6 +335,7 @@ protected function logQueryToFile(string $sql): void {
 			// FIXME:  Improve to log the actual target db host
 			$isPrimary = $this->connections['primary'] === $this->_conn;
 			$prefix .= ' ' . ($isPrimary === true ? 'primary' : 'replica') . ' ';
+			$prefix .= ' ' . $this->getTransactionNestingLevel() . ' ';
 
 			file_put_contents(
 				$this->systemConfig->getValue('query_log_file', ''),
@@ -645,4 +648,30 @@ protected function performConnect(?string $connectionName = null): bool {
 		}
 		return $result;
 	}
+
+	public function beginTransaction() {
+		if (!$this->inTransaction()) {
+			$this->transactionActiveSince = microtime(true);
+		}
+		return parent::beginTransaction();
+	}
+
+	public function commit() {
+		$result = parent::commit();
+		if ($this->getTransactionNestingLevel() === 0) {
+			$timeTook = microtime(true) - $this->transactionActiveSince;
+			$this->transactionActiveSince = null;
+			if ($timeTook > 1) {
+				$this->logger->warning('Transaction took longer then 1s: ' . $timeTook, ['exception' => new \Exception('Long running transaction')]);
+			}
+		}
+		return $result;
+	}
+
+	public function rollBack() {
+		$result = parent::rollBack();
+		if ($this->getTransactionNestingLevel() === 0) {
+			$this->transactionActiveSince = null;
+		}
+	}
 }