Enhance GracefulShutdownHandler to prevent duplicate shutdown execution

- Added checks in `_handle_sigint` and `_handle_sigterm` methods to ignore signals if a shutdown is already in progress, improving robustness and logging clarity.

Author: William-W-Chen

py_spring_core/core/interfaces/graceful_shutdown_handler.py

@@ -39,6 +39,11 @@ def __init__(self, timeout_seconds: float, timeout_enabled: bool) -> None:
 
     def _handle_sigint(self, signum: int, frame: Optional[FrameType]) -> None:
         try:
+            # Check if shutdown is already in progress to prevent duplicate execution
+            if self._shutdown_event.is_set():
+                logger.debug("[Signal] SIGINT ignored - shutdown already in progress")
+                return
+            
             logger.info("[Signal] SIGINT received")
             self._shutdown_type = ShutdownType.MANUAL
             self._shutdown_event.set()
@@ -49,6 +54,11 @@ def _handle_sigint(self, signum: int, frame: Optional[FrameType]) -> None:
 
     def _handle_sigterm(self, signum: int, frame: Optional[FrameType]) -> None:
         try:
+            # Check if shutdown is already in progress to prevent duplicate execution
+            if self._shutdown_event.is_set():
+                logger.debug("[Signal] SIGTERM ignored - shutdown already in progress")
+                return
+            
             logger.info("[Signal] SIGTERM received")
             self._shutdown_type = ShutdownType.SIGTERM
             self._shutdown_event.set()
@@ -111,17 +121,6 @@ def get_shutdown_elapsed_time(self) -> Optional[float]:
             return None
         return time.time() - self._shutdown_start_time
 
-    def trigger_manual_shutdown(self, shutdown_type: ShutdownType = ShutdownType.MANUAL) -> None:
-        """Manually trigger shutdown without signal."""
-        try:
-            logger.info(f"[Manual Shutdown] Triggering manual shutdown: {shutdown_type.name}")
-            self._shutdown_type = shutdown_type
-            self._shutdown_event.set()
-            self._start_shutdown_timer()
-            self.on_shutdown(shutdown_type)
-        except Exception as error:
-            self.on_error(error)
-
     @abstractmethod
     def on_shutdown(self, shutdown_type: ShutdownType) -> None:
         """