>>> We only use java servlets.
In that case, I am presuming you have a "first point of contact" servlet, like a login action or something. Anyway, in this servlet, declare a class variable and initialize on the init() method. Then in your doPost() or doGet() methods, increment the counter each time the method is called. Then in the destroy() method, save the counter to a file/db, and read in again in init() when tomcat is restarted ...