private function quit()
    {
        $this->output->writeln('Stopping the process manager.');

        // this method is also called during startup when something crashed, so
        // make sure we don't operate on nulls.
        if ($this->controller) {
            @$this->controller->close();
        }
        if ($this->web) {
            @$this->web->close();
        }

        if ($this->loop) {
            $this->loop->stop();
        }

        unlink($this->pidfile);
        exit;
    }