protected function installSignals()
    {
        $worker = $this;
        swoole_process::signal(SIGTERM, function() use($worker) {
            $worker->stop();
        });
        swoole_process::signal(SIGINT, function() use($worker) {
            $worker->stop();
        });
        swoole_process::signal(SIGQUIT, function() use($worker) {
            $worker->stop();
        });
        swoole_process::signal(SIGCHLD, function() use($worker) {
            $worker->handleWorkerExit();
        });
    }