without removing all all setLevel calls to subloggers? Is this desirable?
I don't understand the problem. If you told hslogger that you didn't want to hear about stuff about "A", why do you not like that it is following your instructions?
Because taht >>don't want to hear abuot "A"<< could have been set without my knowledge. When trouble shooting a problem it could be handy to just get all messages. But when such a use case arrives I can still patch hslogger. mlog (attempt to create a minimal alternative) ==== I've tried writing another minimal logging system. The idea was driven by adding the possibility to add a handler logging everything not matter what levels are set to different loggers or handlers. The design is simple: keep a list of log handlers and a list of filters. you can add a filter telling that a log message of "A.B" should not be logged. The actual handler function then looks like this log shouldbeLogged logmessage loggername prio = .... So you can still ignore shouldbeLogged easily. However I couldn't even come close to the speed of hslogger even when caching the list of handlers which are supposed to log the message. [some code snippets see end of mail] without any attached handlers: hslogger*[1] : 4ms mlog[2]: 12ms with one default stderr logger (./test 2> /dev/null) hslogger*[1] : 109ms mlog[2]: 150ms [1]: my modified version of hslogger (git://mawercer.de/hslogger) [2]: (git://mawercer.de/mlog) I've tried doing some investigation figuring out why my lib is that much slower but I failed. I noticed that -O2 had an impact on how often the list of generated test cases is run. But that has been all. I don't even use existential types! So I'll shut up and keep using hslogger. Thanks to you John Goerzen for your support. I've learned that I'm very bad at troubleshooting performance. I really thought I could make mlog faster than hslogger*. Using profiling (-P) didn't reveal the source wasting CPU cycles to me. Sincerly Marc Weber [ some code snippets of mlog] the global logger data looks like this: data GlobalLoggerData = GlobalLoggerData { handlers :: M.Map Int LogHandler -- assign a key so that this logger can be removed easily again ,filters :: M.Map Int GlobalFilter -- allow to add global filters -- cache information about which logger accepts what logging data -- String = Priority : loggername , cached :: M.Map String (Bool, [ LogMessageAction ]) } {-# NOINLINE globalLoggerData #-} globalLoggerData :: MVar GlobalLoggerData globalLoggerData = unsafePerformIO $ newMVar $ GlobalLoggerData M.empty M.empty M.empty -- add default handler: addHandler $ LogHandler { accept = \ln p -> True -- which logging events does this log handler accept? ,logAction = \ln p msg doLog -> hPutStrLn stderr msg ,close = return () }