More Servlets and JavaServer Pages™

10.8. Example: A Listener That Counts Sessions

Session tracking can significantly increase the server’s memory load. For example, if a site that uses session tracking has 1,000 unique visitors per hour and the server uses a two-hour session timeout, the system will have approximately 2,000 sessions in memory at any one time. Reducing the timeout to one hour would cut the session memory requirements in half but would risk having active sessions prematurely time out. You need to track typical usage before you can decide on the appropriate solution.

So, you need a listener that will keep track of how many sessions are created, how many are destroyed, and how many are in memory at any one time. Assuming that you have no explicit calls to invalidate ...