TLevel was added to extends log4j's Level, so specific log information could be tracked in the logs. However, that's a less than ideal way of adding log information, and it forces us to use log4j, and could result in some confusion when trying to create a log4j configuration file to deal with these separately.
Loggers have names (typically a class name, but it could be anything). Instead of using a logger named after the class, it should use a name "TABLET_HIST" to replace what TLevel is currently doing. Alternatively, we can construct a simple slf4j logger which wraps the one from the LoggerFactory and adds "TABLET_HIST" as a prefix to logs written with this logger.