From 5f9fa15a6ad4fac206b814fdf2537eee78a818db Mon Sep 17 00:00:00 2001
From: dgtlmoon <dgtlmoon@gmail.com>
Date: Thu, 19 Mar 2026 18:02:07 +0100
Subject: [PATCH] Realtime - Suppress socket.io errors in logs (#3991)

---
 changedetectionio/realtime/socket_server.py | 23 +++++++++++++++++++++
 changedetectionio/static/js/realtime.js     |  8 +++++++
 2 files changed, 31 insertions(+)

diff --git a/changedetectionio/realtime/socket_server.py b/changedetectionio/realtime/socket_server.py
index c9b48c5e9..3c20c285a 100644
--- a/changedetectionio/realtime/socket_server.py
+++ b/changedetectionio/realtime/socket_server.py
@@ -199,8 +199,31 @@ def handle_watch_update(socketio, **kwargs):
         logger.error(f"Socket.IO error in handle_watch_update: {str(e)}")
 
 
+def _suppress_werkzeug_ws_abrupt_disconnect_noise():
+    """Patch BaseWSGIServer.log to suppress the AssertionError traceback that fires when
+    a browser closes a WebSocket connection mid-handshake (e.g. closing a tab).
+    The exception is caught inside run_wsgi and routed to self.server.log() — it never
+    propagates out, so wrapping run_wsgi doesn't help. Patching the log method is the
+    only reliable intercept point. The error is cosmetic: Socket.IO already handles the
+    disconnect correctly via its own disconnect handler and timeout logic."""
+    try:
+        from werkzeug.serving import BaseWSGIServer
+        _original_log = BaseWSGIServer.log
+
+        def _filtered_log(self, type, message, *args):
+            if type == 'error' and 'write() before start_response' in message:
+                return
+            _original_log(self, type, message, *args)
+
+        BaseWSGIServer.log = _filtered_log
+    except Exception:
+        pass
+
+
 def init_socketio(app, datastore):
     """Initialize SocketIO with the main Flask app"""
+    _suppress_werkzeug_ws_abrupt_disconnect_noise()
+
     import platform
     import sys
 
diff --git a/changedetectionio/static/js/realtime.js b/changedetectionio/static/js/realtime.js
index 474b2df0b..9d52546ce 100644
--- a/changedetectionio/static/js/realtime.js
+++ b/changedetectionio/static/js/realtime.js
@@ -116,6 +116,14 @@ $(document).ready(function () {
                 $('#realtime-conn-error').show();
             });
 
+            // Tell the server we're leaving cleanly so it can release the connection
+            // immediately rather than waiting for a timeout.
+            // Note: this only fires for voluntary closes (tab/window close, navigation away).
+            // Hard kills, crashes and network drops will still timeout normally on the server.
+            window.addEventListener('beforeunload', function () {
+                socket.disconnect();
+            });
+
             socket.on('queue_size', function (data) {
                 console.log(`${data.event_timestamp} - Queue size update: ${data.q_length}`);
                 if(queueSizePagerInfoText) {