Log Formatter

color_logger.rb

# Patterned after this LogFormatter:
#   https://github.com/QutBioacousticsResearchGroup/bioacoustic-workbench/blob/master/config/initializers/log_formatting.rb
# And some of this:
#   http://95.154.230.254/ip-1/encoded/Oi8vcGFzdGViaW4uY29tL1hxRU1keGRT
# Makes as much as possible constant values to not bog down GC and make it whip fast

class ColorLogger
  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 = begin
    if ENV['LOG_HUMOR']
      ENV['LOG_HUMOR'] != 'false' # Default to true
    else
      Rails.env.development?
    end
  end
  USE_COLOR = begin
    if ENV['LOG_COLOR']
      ENV['LOG_COLOR'] != 'false' # Default to true
    else
      Rails.env.development?
    end
  end

  THIS_FILE_PATH = File.expand_path(".")

  FORMATTED_SEVERITY = USE_HUMOROUS_SEVERITIES ?
      lambda { |severity| sprintf("%-3s", "#{SEVERITY_TO_TAG_MAP[severity]}") } :
      lambda { |severity| sprintf("%-5s", "#{severity}") }

  FORMATTED_MESSAGE = if USE_COLOR
                        lambda { |severity, formatted_time, msg|
                          color = SEVERITY_TO_COLOR_MAP[severity]
                          "[\033[#{color}m#{formatted_time}\033[0m] [\033[#{color}m#{FORMATTED_SEVERITY.call(severity)}\033[0m] #{msg.strip}\n"
                        }
                      else
                        lambda { |severity, formatted_time, msg|
                          "[#{formatted_time}] [#{FORMATTED_SEVERITY.call(severity)}] #{msg.strip}\n"
                        }
                      end

  def exception_values(e)
    trace = e.backtrace.select { |x| !line.starts_with?(THIS_FILE_PATH) }
    trace = trace.map { |l| colorize_exception(l) } if USE_COLOR
    first = "\n" + trace.first + ": " + e.message + " (#{e.class})"
    rest = "\t" + trace[1..-1].join("\n\t")
    return first + "\n" + rest
  end

  def colorize_exception(line)
    "\033[01;32m#{line}\033[0m"
  end

  def call(severity, time, progname, msg)
    formatted_time = time.strftime("%Y-%m-%d %H:%M:%S.") << time.usec.to_s[0..2].rjust(3)
    text = if msg.is_a? String
             msg
           elsif msg.is_a? Exception
             " --> Exception: " + exception_values(msg)
           else
             "!!!!! UNKNOWN TYPE: #{msg.class}" + msg.to_s
           end
    FORMATTED_MESSAGE.call(severity, formatted_time, text)
  end

end

This has been turned into a gem: https://github.com/pboling/humorous_log_formatter