Check phantomjs service before rewrite url

Hi!

I have web server based on IIS that serves SPA application. Also I installed phantomjs as Windows Service and configure it to prerender SPA appilcation when search bots crowling the site. If request is done by Google f.i. IIS rewrite url and request is handled by phantomjs.

What I need is to check if phantomjs is alive before rewrite url.

Is there any idea guys?

I think about CGI. For eaxmple cacth the request, check if it is from Google and check if phantomjs is alive. And so on. But not sure if it real solution.