fix: suppress closure errors in runnersupervisor and force spawn start method (#1547)

some errors could be thrown during shutdown - we can dismiss these safely

co-authored by me :)

src/exo/main.py

@@ -252,7 +252,7 @@ def main():
     target = min(max(soft, 65535), hard)
     resource.setrlimit(resource.RLIMIT_NOFILE, (target, hard))
 
-    mp.set_start_method("spawn")
+    mp.set_start_method("spawn", force=True)
     # TODO: Refactor the current verbosity system
     logger_setup(EXO_LOG, args.verbosity)
     logger.info("Starting EXO")

src/exo/worker/runner/runner_supervisor.py

@@ -106,13 +106,18 @@ class RunnerSupervisor:
     def shutdown(self):
         logger.info("Runner supervisor shutting down")
         self._tg.cancel_tasks()
-        self._ev_recv.close()
-        self._task_sender.close()
         if not self._cancel_watch_runner.cancel_called:
             self._cancel_watch_runner.cancel()
+        with contextlib.suppress(ClosedResourceError):
+            self._ev_recv.close()
+        with contextlib.suppress(ClosedResourceError):
+            self._task_sender.close()
+        with contextlib.suppress(ClosedResourceError):
+            self._event_sender.close()
         with contextlib.suppress(ClosedResourceError):
             self._cancel_sender.send(TaskId("CANCEL_CURRENT_TASK"))
-        self._cancel_sender.close()
+        with contextlib.suppress(ClosedResourceError):
+            self._cancel_sender.close()
         self.runner_process.join(5)
         if not self.runner_process.is_alive():
             logger.info("Runner process succesfully terminated")