fix: improve graceful shutdown and null safety

  - Add dynamic wait times for event queue shutdown (5s if events
  pending, 1s if empty)
  - Fix signal handler to prevent recursive calls and ensure clean exit
  - Add null check for request parameters in MCP server
  - Update mcpcat-api dependency to 0.1.4

Author: naji247

pyproject.toml

@@ -19,7 +19,7 @@ classifiers = [
 ]
 dependencies = [
     "mcp>=1.2.0",
-    "mcpcat-api==0.1.3",
+    "mcpcat-api==0.1.4",
     "pydantic>=2.0.0",
 ]
 

src/mcpcat/modules/event_queue.py

@@ -3,6 +3,7 @@
 import atexit
 import queue
 import signal
+import os
 import threading
 import time
 from datetime import datetime, timezone
@@ -141,28 +142,46 @@ def destroy(self) -> None:
         self._shutdown = True
         self._shutdown_event.set()
 
-        # Wait for queue to drain (with timeout)
-        timeout = 5.0  # 5 seconds
-        start = time.time()
+        # Determine wait time based on queue state
+        if self.queue.qsize() > 0:
+            # If there are events in queue, wait 5 seconds
+            wait_time = 5.0
+            write_to_log(f"Shutting down with {self.queue.qsize()} events in queue, waiting up to {wait_time}s")
+        else:
+            # If queue is empty, just wait 1 second for in-flight requests
+            wait_time = 1.0
+            write_to_log(f"Queue empty, waiting {wait_time}s for in-flight requests")
 
-        while self.queue.qsize() > 0 and time.time() - start < timeout:
-            time.sleep(0.1)
+        # Wait for the specified time
+        time.sleep(wait_time)
 
-        # Shutdown executor
-        # Note: timeout parameter was added in Python 3.9 but removed in later versions
+        # Shutdown executor (this will wait for running tasks to complete)
         self.executor.shutdown()
 
-        if self.queue.qsize() > 0:
-            write_to_log(f"Shutting down with {self.queue.qsize()} events still in queue")
+        # Log final status
+        remaining = self.queue.qsize()
+        if remaining > 0:
+            write_to_log(f"Shutdown complete. {remaining} events were not processed.")
 
 
 # Global event queue instance
 event_queue = EventQueue()
 
 
-def _shutdown_handler(*_):
+def _shutdown_handler(signum, frame):
     """Handle shutdown signals."""
+    
+    write_to_log("Received shutdown signal, gracefully shutting down...")
+    
+    # Reset signal handlers to default behavior to avoid recursive calls
+    signal.signal(signal.SIGINT, signal.SIG_DFL)
+    signal.signal(signal.SIGTERM, signal.SIG_DFL)
+    
+    # Perform graceful shutdown
     event_queue.destroy()
+    
+    # Force exit after graceful shutdown
+    os._exit(0)
 
 
 def set_event_queue(new_queue: EventQueue) -> None:

src/mcpcat/modules/overrides/mcp_server.py

@@ -65,7 +65,7 @@ async def wrapped_list_tools_handler(request: ListToolsRequest) -> ServerResult:
         event = UnredactedEvent(
             session_id=session_id,
             timestamp=datetime.now(timezone.utc),
-            parameters=request.params.model_dump() if request.params else {},
+            parameters=request.params.model_dump() if request and request.params else {},
             event_type=EventType.MCP_TOOLS_LIST.value,
         )
 

tests/test_event_queue.py

@@ -602,16 +602,25 @@ def test_shutdown_handlers_registered(mock_atexit, mock_signal):
     assert mock_atexit.called
 
 
+@patch('os._exit')
+@patch('mcpcat.modules.event_queue.signal.signal')
 @patch('mcpcat.modules.event_queue.event_queue')
-def test_shutdown_handler_function(mock_event_queue):
+def test_shutdown_handler_function(mock_event_queue, mock_signal, mock_exit):
     """Test the _shutdown_handler function."""
     from mcpcat.modules.event_queue import _shutdown_handler
 
-    # Call the shutdown handler
-    _shutdown_handler()
+    # Call the shutdown handler with proper signal handler arguments
+    _shutdown_handler(signal.SIGINT, None)
+    
+    # Verify signal handlers are reset to default
+    mock_signal.assert_any_call(signal.SIGINT, signal.SIG_DFL)
+    mock_signal.assert_any_call(signal.SIGTERM, signal.SIG_DFL)
 
     # Verify it calls destroy on the event queue
     mock_event_queue.destroy.assert_called_once()
+    
+    # Verify it exits with code 0
+    mock_exit.assert_called_once_with(0)
 
 
 @patch('sys.version_info', (3, 8, 0))