protected function getRunningPid()
    {
        if (!file_exists($this->pidFilePath)) {
            return;
        }

        $pid = intval(trim(file_get_contents($this->pidFilePath)));

        if($this->processControl->isRunning($pid, true)) {
            return $pid;
        }

        // Not found, remove the stale PID file
        unlink($this->pidFilePath);
    }