Beautiful logging for Ruby on Rails 4

In a previous post I showed you a simple way to get beautiful, easy-to-read logs in your Rails 3.2 application. Rails 4 changed the game again; for Rails 3.2 or earlier, refer to my earlier post; but for Rails 4 read on…

It’s really easy. Just make a new file in your ‘config/initializers’ directory called something like ‘log_formatting.rb’ and paste into it the following code. Restart your app, and voila: pretty logs again!

UPDATED. Konrad’s comment below was correct. I’ve altered this code to work with both the regular logger and the new tagged logger. Now you can configure your logger as

config.logger = ActiveSupport::Logger.new('your_app.log')

or

config.logger = ActiveSupport::TaggedLogging.new(Logger.new('your_app.log'))

… both will work. Here’s the updated monkey patch:

class ActiveSupport::Logger::SimpleFormatter
  SEVERITY_TO_TAG_MAP     = {'DEBUG'=>'meh', 'INFO'=>'fyi', 'WARN'=>'hmm', 'ERROR'=>'wtf', 'FATAL'=>'omg', 'UNKNOWN'=>'???'}
  SEVERITY_TO_COLOR_MAP   = {'DEBUG'=>'0;37', 'INFO'=>'32', 'WARN'=>'33', 'ERROR'=>'31', 'FATAL'=>'31', 'UNKNOWN'=>'37'}
  USE_HUMOROUS_SEVERITIES = true

  def call(severity, time, progname, msg)
    if USE_HUMOROUS_SEVERITIES
      formatted_severity = sprintf("%-3s",SEVERITY_TO_TAG_MAP[severity])
    else
      formatted_severity = sprintf("%-5s",severity)
    end

    formatted_time = time.strftime("%Y-%m-%d %H:%M:%S.") << time.usec.to_s[0..2].rjust(3)
    color = SEVERITY_TO_COLOR_MAP[severity]

    "\033[0;37m#{formatted_time}\033[0m [\033[#{color}m#{formatted_severity}\033[0m] #{msg.strip} (pid:#{$$})\n"
  end
end