Since I'm D n00b I'll just post a couple of observations:
* I agree that it is a good idea just to use few log levels.
* I think is it is a misstake not to let formatting of the whole
log message be pluggable (i.e. not the free text message the
programmer writes). If I have created a special RFC5424 formatter
(with MSGID and STRUCTURED-DATA fields set according to the will
of my corporate masters) I want to resuse it in both the
FileLogger and a future TcpLogger without having to use
inheritance. Your "line format" formatter in FileLogger is a good
default formatter though.
///Kalle
