We have only a very small number of customers (fewer than 50) and we would like each one to have its own separate log file into which all of its server side logging info goes. I know you could use NDC and filters to direct log statements to different files using the standard appenders in Log4j but that would require quite a bit more setup (to create loggers for all existing customers) and it wouldn't automatically accomodate the addition of a new customer into the system. Have you ever seen an appender which would split out log statements to separate files based on the Log4j NDC value? I figure I could build a new appender to do it but I can't say I want to if I can get something already built that works well.