IMO, your requirements are too basic to need a serious system. Either log interaction to a file or a database, parse the output and query it with SQL to produce your basic metrics, or just write to Google Analytics.
When this starts creaking at the seams it'll mean that you either have bigger analysis and/or scalability requirements and it'll much clearer what you need to look for.
When this starts creaking at the seams it'll mean that you either have bigger analysis and/or scalability requirements and it'll much clearer what you need to look for.