Question

It appears that we have access to Rails.logger and logger inside Rails applications. I understand that the two logger are different, but wouldnt it be ideal to create on TaggedBufferedLogger and have a single instance for logger. Why are there two instances and what is the proper time to use which?

Answer 1

BufferedLogger is the default Rails logger. Its purpose is to make logging thread-safe.
Optionally, you can wrap this logger into a TaggedBufferedLogger and use it, if you want to ‘tag’ your logging output.

Straight from the weblog.rails

Tagged logger

When you’re running a multi-user, multi-account application, it’s a great help to be able to filter the log by who did what. Enter the TaggedLogging wrapper. It works like this:  

Logger = ActiveSupport::TaggedLogging.new(Logger.new(STDOUT))
Logger.tagged("BCX") { Logger.info "Stuff" } # Logs "[BCX] Stuff"
Logger.tagged("BCX") do
  Logger.tagged("Jason") do
    Logger.info "Stuff" # Logs "\[BCX\] \[Jason\] Stuff"
  end
end