I build server applications and when something goes wrong, I need to be able to enable logging and have the application notice the change without a restart. My application have no gui, so manually "poking" the application is awkward and ugly.

Note that I disagree with the suggestion to check if the file has changed on each log statement. My application's performance goals are measured in microseconds (time to respond to a message by sending another message), any additional latency is a big problem for me. I'd like to be able to configure the frequency of checking the file, but it isn't super important.

Ideally, I'd like to be able to specify that the config file should be watched IN the config file, rather than programatically.