I need to extend the log4j framework to provide stats on how many messages were emitted at each configured level. Does anybody know of any prior research done in this direction ? Any pointers on how to go about extending log4j to enable this functionality and/or links to advanced tutorials & other material will be much appreciated.

At present I am thinking of creating a custom filter that merely notes down the level of each message and returns true, in effect keeping a running count of the messages. And by creating a NullAppender and adding this filter to it I should probably be home. Any better ideas ?