Fix shutdown event on Windows in reloader (#1584)

Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>

setup.cfg

@@ -47,6 +47,7 @@ exclude_lines =
 [coverage:coverage_conditional_plugin]
 rules =
   "sys_platform == 'win32'": py-win32
+  "sys_platform != 'win32'": py-not-win32
   "sys_platform == 'linux'": py-linux
   "sys_platform == 'darwin'": py-darwin
   "sys_version_info >= (3, 8)": py-gte-38

tests/supervisors/test_reload.py

@@ -1,6 +1,7 @@
 import logging
 import signal
 import socket
+import sys
 from pathlib import Path
 from time import sleep
 from typing import Optional, Type
@@ -393,7 +394,10 @@ def test_base_reloader_should_exit(tmp_path):
     assert not reloader.should_exit.is_set()
     reloader.pause()
 
-    reloader.signal_handler(signal.SIGINT, None)
+    if sys.platform == "win32":
+        reloader.signal_handler(signal.CTRL_C_EVENT, None)  # pragma: py-not-win32
+    else:
+        reloader.signal_handler(signal.SIGINT, None)  # pragma: py-win32
 
     assert reloader.should_exit.is_set()
     with pytest.raises(StopIteration):

uvicorn/supervisors/basereload.py

@@ -1,6 +1,7 @@
 import logging
 import os
 import signal
+import sys
 import threading
 from pathlib import Path
 from socket import socket
@@ -32,13 +33,17 @@ def __init__(
         self.sockets = sockets
         self.should_exit = threading.Event()
         self.pid = os.getpid()
+        self.is_restarting = False
         self.reloader_name: Optional[str] = None
 
     def signal_handler(self, sig: int, frame: Optional[FrameType]) -> None:
         """
         A signal handler that is registered with the parent process.
         """
-        self.should_exit.set()
+        if sys.platform == "win32" and self.is_restarting:
+            self.is_restarting = False  # pragma: py-not-win32
+        else:
+            self.should_exit.set()  # pragma: py-win32
 
     def run(self) -> None:
         self.startup()
@@ -80,7 +85,12 @@ def startup(self) -> None:
         self.process.start()
 
     def restart(self) -> None:
-        self.process.terminate()
+        if sys.platform == "win32":  # pragma: py-not-win32
+            self.is_restarting = True
+            assert self.process.pid is not None
+            os.kill(self.process.pid, signal.CTRL_C_EVENT)
+        else:  # pragma: py-win32
+            self.process.terminate()
         self.process.join()
 
         self.process = get_subprocess(
@@ -89,7 +99,10 @@ def restart(self) -> None:
         self.process.start()
 
     def shutdown(self) -> None:
-        self.process.terminate()
+        if sys.platform == "win32":
+            self.should_exit.set()  # pragma: py-not-win32
+        else:
+            self.process.terminate()  # pragma: py-win32
         self.process.join()
 
         for sock in self.sockets: