Find total active user sessions / online users in Windows Azure with multiple instances scenario

Question

Is there any way using which we can find the total number of active users in a ASP.NET MVC web application which is deployed on windows azure with multiple web role instances.

Application uses Azure ACS and there is no session involved i.e. it is not using any distributed cache to store sessions across role instances.

I am aware about in general how this is achieved i.e. using the application object variable where you initialize it in the App_Start and then increment or decrement in Session_Start / Session_End methods but this wont work in multiple instance scenarios as session is not distributed across the web role instances.