Register existing signal handlers in simpervisor's atexit module

simpervisor/atexitasync.py

@@ -7,17 +7,39 @@
 import sys
 
 _handlers = []
+_existing_handlers = {}
 
 signal_handler_set = False
 
 
 def add_handler(handler):
     global signal_handler_set
     if not signal_handler_set:
+        # Add handler of SIGINT only if it is not default
+        _existing_sigint_handler = signal.getsignal(signal.SIGINT)
+        if _existing_sigint_handler.__qualname__ == "default_int_handler":
+            _existing_sigint_handler = None
+        _existing_handlers.update(
+            {
+                signal.SIGINT: _existing_sigint_handler,
+            }
+        )
+
+        # Add handler of SIGTERM only if it is not default
+        _existing_sigterm_handler = signal.getsignal(signal.SIGTERM)
+        if _existing_sigterm_handler == signal.Handlers.SIG_DFL:
+            _existing_sigterm_handler = None
+        _existing_handlers.update(
+            {
+                signal.SIGTERM: _existing_sigterm_handler,
+            }
+        )
+
         signal.signal(signal.SIGINT, _handle_signal)
         signal.signal(signal.SIGTERM, _handle_signal)
         signal_handler_set = True
     _handlers.append(handler)
+    # print(_existing_handlers)
 
 
 def remove_handler(handler):
@@ -31,4 +53,10 @@ def _handle_signal(signum, *args):
         signum = signal.CTRL_C_EVENT
     for handler in _handlers:
         handler(signum)
-    sys.exit(0)
+    # Finally execute any existing handler that were registered in Python
+    # Bail if existing handler is not a callable
+    existing_handler = _existing_handlers.get(signum, None)
+    if existing_handler is not None and callable(existing_handler):
+        existing_handler(signum, None)
+    else:
+        sys.exit(0)