Log4r[1] is nice, but last I checked it isn't as well maintained or feature rich as the Logging[2] gem.
[1] https://rubygems.org/gems/log4r [2] https://rubygems.org/gems/logging
You get pretty much all of that and with less verbose configuration with the Logging gem + lograge, yet they are still relatively easy to tweak. The email notification of the Logging/Logging-rails gem in particular is really great, and you can even define message thresholds (not more than one email per minute, only if X number of errors etc)
Sadly the docs are even worse than the ones for Log4R. I will take a look into writing another blogpost as an introduction to Logger as well as the differences and advantages of Logger. Thanks for making me aware of this gem!