Use a more thorough cleanup of parallel workers (#21981)

Ref #21905

Hopefully this will reduce parallel test flakiness on heavy load
machines.

Author: ilevkivskyi

mypy/build.py

@@ -315,10 +315,11 @@ def close(self) -> None:
         if self.connected:
             self.conn.close()
         # Technically we don't need to wait, but otherwise we will get ResourceWarnings.
+        # Also, it is generally good to not leave some running worker processes behind.
         try:
             self.proc.wait(timeout=WORKER_SHUTDOWN_TIMEOUT)
         except subprocess.TimeoutExpired:
-            pass
+            self.proc.terminate()
         if os.path.isfile(self.status_file):
             os.unlink(self.status_file)
 

mypy/defaults.py

@@ -51,7 +51,7 @@
 # with our generous timeouts, so we set them higher.
 WORKER_START_INTERVAL: Final = 0.01 if sys.platform != "win32" else 0.03
 WORKER_START_TIMEOUT: Final = 3 if sys.platform != "win32" else 10
-WORKER_SHUTDOWN_TIMEOUT: Final = 1 if sys.platform != "win32" else 3
+WORKER_SHUTDOWN_TIMEOUT: Final = 3 if sys.platform != "win32" else 10
 
 WORKER_CONNECTION_TIMEOUT: Final = 10
 WORKER_IDLE_TIMEOUT: Final = 600