Redmine

How would this work in a multi process deployment where there are several processes writing to the log file at once?

Well, I just assumed that as Logger is part of stdlib it would take care of it, but I went digging in the ruby core_ext directory, and found logger.rb and monitor.rb. Short version: Logger uses a mutex through MonitorMixin. Long version: take a look at Logger#initialize (line 256) and LogDevice (line 473) in logger.rb and MonitorMixin (basically the whole file) in monitor.rb (lines apply for the OS X.6 version of 1.8.7, don't know how "vanilla" it is).