1 files changed, 78 insertions, 0 deletions
diff --git a/apps/dav/lib/Connector/Sabre/PropFindMonitorPlugin.php b/apps/dav/lib/Connector/Sabre/PropFindMonitorPlugin.php
new file mode 100644
index 00000000000..130d4562146
--- /dev/null
+++ b/apps/dav/lib/Connector/Sabre/PropFindMonitorPlugin.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types = 1);
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCA\DAV\Connector\Sabre;
+
+use Sabre\DAV\Server as SabreServer;
+use Sabre\DAV\ServerPlugin;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+
+/**
+ * This plugin runs after requests and logs an error if a plugin is detected
+ * to be doing too many SQL requests.
+ */
+class PropFindMonitorPlugin extends ServerPlugin {
+
+	/**
+	 * A Plugin can scan up to this amount of nodes without an error being
+	 * reported.
+	 */
+	public const THRESHOLD_NODES = 50;
+
+	/**
+	 * A plugin can use up to this amount of queries per node.
+	 */
+	public const THRESHOLD_QUERY_FACTOR = 1;
+
+	private SabreServer $server;
+
+	public function initialize(SabreServer $server): void {
+		$this->server = $server;
+		$this->server->on('afterResponse', [$this, 'afterResponse']);
+	}
+
+	public function afterResponse(
+		RequestInterface $request,
+		ResponseInterface $response): void {
+		if (!$this->server instanceof Server) {
+			return;
+		}
+
+		$pluginQueries = $this->server->getPluginQueries();
+		if (empty($pluginQueries)) {
+			return;
+		}
+		$maxDepth = max(0, ...array_keys($pluginQueries));
+		// entries at the top are usually not interesting
+		unset($pluginQueries[$maxDepth]);
+
+		$logger = $this->server->getLogger();
+		foreach ($pluginQueries as $depth => $propFinds) {
+			foreach ($propFinds as $pluginName => $propFind) {
+				[
+					'queries' => $queries,
+					'nodes' => $nodes
+				] = $propFind;
+				if ($queries === 0 || $nodes > $queries || $nodes < self::THRESHOLD_NODES
+					|| $queries < $nodes * self::THRESHOLD_QUERY_FACTOR) {
+					continue;
+				}
+				$logger->error(
+					'{name} scanned {scans} nodes with {count} queries in depth {depth}/{maxDepth}. This is bad for performance, please report to the plugin developer!', [
+						'name' => $pluginName,
+						'scans' => $nodes,
+						'count' => $queries,
+						'depth' => $depth,
+						'maxDepth' => $maxDepth,
+					]
+				);
+			}
+		}
+	}
+}