def call_nowait(self, cmd: List[str]) -> None:
        """Run one `on_reload` callback at most.

        To achieve it we always kill already running command including child processes."""
        self.cancel(kill=True)
        self._kill_children()
        with self._lock:
            started = self._start_process(cmd, close_fds=True)
        if started and self._process is not None:
            Thread(target=self._process.wait).start()
Run one `on_reload` callback at most.

        To achieve it we always kill already running command including child processes.
patroni/postgresql/callback_executor.py