Update app.py

app.py

@@ -19,26 +19,27 @@ HISTORY_DURATION_SECONDS = 60 * 60
 # Structure: { "id": "uuid", "url": "string", "status": "pending/ok/error/checking",
 #              "ip": "string", "responseTime": float_ms, "lastChecked": "iso_string_utc",
 #              "history": [{"timestamp": float_unix_ts_seconds, "status": "ok/error"}],
-#              "userId": "string_user_uuid", # ADDED: To associate URL with a user
+#              "userId": "string_user_uuid",
 #              "_thread": threading.Thread_object, "_stop_event": threading.Event_object }
 monitored_urls_store = {}
-lock = threading.Lock()
+lock = threading.Lock() # Non-reentrant lock
 
 # --- Helper Functions ---
 def save_data_to_json():
-    with lock: # Ensure lock is acquired before calling if called externally
-        serializable_data = {}
-        for url_id, data in monitored_urls_store.items():
-            s_data = data.copy()
-            s_data.pop("_thread", None)
-            s_data.pop("_stop_event", None)
-            serializable_data[url_id] = s_data
-        try:
-            with open(DATA_FILE, 'w') as f:
-                json.dump(serializable_data, f, indent=2)
-            print(f"Data saved to {DATA_FILE}")
-        except IOError as e:
-            print(f"Error saving data to {DATA_FILE}: {e}")
+    # This function must be called with 'lock' acquired
+    # REMOVED 'with lock:' from here as callers already acquire it.
+    serializable_data = {}
+    for url_id, data in monitored_urls_store.items():
+        s_data = data.copy()
+        s_data.pop("_thread", None)
+        s_data.pop("_stop_event", None)
+        serializable_data[url_id] = s_data
+    try:
+        with open(DATA_FILE, 'w') as f:
+            json.dump(serializable_data, f, indent=2)
+        print(f"Data saved to {DATA_FILE}")
+    except IOError as e:
+        print(f"Error saving data to {DATA_FILE}: {e}")
 
 def load_data_from_json():
     global monitored_urls_store
@@ -57,7 +58,7 @@ def load_data_from_json():
                 data_item.setdefault('responseTime', None)
                 data_item.setdefault('lastChecked', None)
                 data_item.setdefault('history', data_item.get('history', []))
-                data_item.setdefault('userId', None) # ADDED: Handle old data without userId
+                data_item.setdefault('userId', None)
                 temp_store[current_id] = data_item
             
             with lock:
@@ -75,8 +76,6 @@ def load_data_from_json():
     
     url_ids_to_start_monitoring = []
     with lock:
-        # We don't know the user context here, so all threads for loaded URLs are started.
-        # The GET endpoint will filter by user.
         url_ids_to_start_monitoring = list(monitored_urls_store.keys())
 
     for url_id in url_ids_to_start_monitoring:
@@ -170,7 +169,7 @@ def execute_url_check(url_id_to_check):
         live_url_data['history'] = current_history_list
         prune_url_history(live_url_data)
         
-        save_data_to_json()
+        save_data_to_json() # Called while lock is held
         print(f"Finished check for {live_url_data['url']}: {final_check_status}, {http_response_time_ms} ms")
 
 def pinger_thread_function(url_id_param, stop_event_param):
@@ -224,13 +223,12 @@ def serve_index():
 def get_all_urls_for_user():
     user_id = request.headers.get('X-User-ID')
     if not user_id:
-        # Return empty list if no user ID is provided, or could be 400 error
         return jsonify([]), 200
 
     with lock:
         response_list = []
         for data_item in monitored_urls_store.values():
-            if data_item.get('userId') == user_id: # Filter by userId
+            if data_item.get('userId') == user_id:
                 display_item = data_item.copy()
                 display_item.pop("_thread", None)
                 display_item.pop("_stop_event", None)
@@ -263,7 +261,6 @@ def add_new_url_for_user():
     with lock:
         normalized_new_url = input_url.rstrip('/').lower()
         for existing_url_data in monitored_urls_store.values():
-            # Check for duplicates only for the current user
             if existing_url_data.get('userId') == user_id and \
                existing_url_data['url'].rstrip('/').lower() == normalized_new_url:
                 return jsonify({"error": "URL already monitored by you"}), 409
@@ -274,12 +271,12 @@ def add_new_url_for_user():
         url_entry_to_add = {
             "id": new_url_id, "url": input_url, "status": 'pending', 
             "ip": resolved_ip, "responseTime": None, "lastChecked": None, "history": [],
-            "userId": user_id # Associate with the user
+            "userId": user_id
         }
         
         response_payload = url_entry_to_add.copy()
         monitored_urls_store[new_url_id] = url_entry_to_add
-        save_data_to_json() 
+        save_data_to_json() # Called while lock is held
     
     start_url_monitoring_thread(new_url_id)
     return jsonify(response_payload), 201
@@ -295,14 +292,12 @@ def delete_existing_url_for_user(target_url_id):
         if target_url_id in monitored_urls_store:
             url_entry_to_check = monitored_urls_store[target_url_id]
             
-            # Check if the URL belongs to the requesting user
             if url_entry_to_check.get('userId') != user_id:
-                # Do not reveal existence of URL; treat as if not found for this user
                 return jsonify({"error": "URL not found or permission denied"}), 404
 
-            stop_url_monitoring_thread(target_url_id) 
+            stop_url_monitoring_thread(target_url_id) # Must be called with lock held
             removed_url_entry = monitored_urls_store.pop(target_url_id)
-            save_data_to_json()
+            save_data_to_json() # Called while lock is held
             
             response_data = removed_url_entry.copy()
             response_data.pop("_thread", None)