actual request-received time?

There are a number of 'layers' a request must pass through before it actually 'hits' a Rails app (e.g., Apache receives a request, Apache starts a new thread, new thread processes the request and determines that it's for a dynamic resource so Apache thread passes it to Passenger, Passenger passes it to or starts a new Rails process, Rails app begins processing request. ...) Does anyone know if / how it's possible to get at the actual time a request hit the first software layer on the server ?

Thanks, Bill