AuditLogger & Helper functions for Rails applications

audit_logger.rb

=begin
  Usage:

    require 'audit_logger'

    class MyClass
      include AuditLogger::Helpers
      audit_logger_name 'my-class.log'

      # It works in instance methods
      def foo
        # Standard logging
        audit # => "#{self.class}[id:#{id}]##{method}:#{line}"
        
        # Log with a message
        audit 'this message' # => "#{self.class}[id:#{id}]##{method}:#{line}\nthis message"
        
        # If you want to log to a different logfile than the current class default:
        audit log:'mylogger.log'

        # There are several options you can pass in
        audit log:'mylogger.log', body:'this message', level:'error'
      end

      # It works in class or static methods
      def self.foo
        audit # => "#{self}::#{method}:#{line}"
      end

    end

=end
  
end

class AuditLogger < Logger
  cattr_accessor :audit_loggers
  self.audit_loggers = {}
  
  at_exit { AuditLogger.close_all }

  # AuditLogger.[] is the preferred creation method
  def initialize(name, *args)
    # make sure to track any creations
    super
    self.class.audit_loggers[name] = self
  end

  def audit(*args)

  end

  def puts(*args); info args.join "\n\t"; end

  def tabs(*args); info args.join "\t"; end

  def self.file_name(name)
    Rails.root.join('log', "#{name.to_s.downcase}.log").to_s
  end

  def self.[](name)
    name = file_name(name)
    audit_loggers[name] || begin
      # log rotation: keep 25 old log files with 20MB
      AuditLogger.new(name, 25, (2097152*10))
    end
  end

  def self.close_all
    audit_loggers.values.each do |name, logger|
      if logger
        logger.close rescue nil # Ignore
      end
    end

    audit_loggers.clear
  end
  
  def format_message(severity, timestamp, progname, msg)
    "#{timestamp.to_formatted_s(:db)} #{severity} #{msg}\n" 
  end

  module Helpers
    @audit_logger_name = 'default_audit'

    private

    def audit(*args)
      proc = 
      if self.respond_to?(:id)
        lambda{|line, method| "#{self.class}[id:#{id}]##{method}:#{line}" }
      else
        lambda{|line, method| "#{self.class}##{method}:#{line}" }
      end
      self.class._audit proc, args
    end

    def self.included(base)
      base.extend ClassMethods
    end

    module ClassMethods
      def audit(*args)
        _audit lambda{|line, method| "#{self}::#{method}:#{line}"}, args
      end

      def audit_logger_name name
        @audit_logger_name = name
      end

      def _audit header_proc, args
        # build header line
        line, method = _stack_data 2
        header = header_proc.call(line,method)
        # set options
        options = args.first.is_a?(Hash) ? args.first : {body:args}
        log = options[:log] ? AuditLogger[options[:log]] : AuditLogger[@audit_logger_name]
        # build logger output
        output =
        if options[:body]
          body = Array(options[:body]).join options.fetch(:delim, " ")
          [header,body].join options.fetch(:header_delim, "\n\t")
        else
          header
        end
        # write to log, using appropriate log level
        options[:level] ||= :info
        log.send options[:level], output
      end

      # Returns method and line number from backtrace
      def _stack_data caller_steps=0
        match_data = caller[caller_steps].match /:(\d+):in `(.+)'/
        return [match_data[1], match_data[2]]
      end
    end

  end

end 

doc.md

Usage:

    require 'audit_logger'

    class MyClass
      include AuditLogger::Helpers
      audit_logger_name 'my-class.log'

      # It works in instance methods
      def foo
        # Standard logging
        audit # => "#{self.class}[id:#{id}]##{method}:#{line}"
        
        # Log with a message
        audit 'this message' # => "#{self.class}[id:#{id}]##{method}:#{line}\nthis message"
        
        # If you want to log to a different logfile than the current class default:
        audit log:'mylogger.log'

        # There are several options you can pass in
        audit log:'mylogger.log', body:'this message', level:'error'
      end

      # It works in class or static methods
      def self.foo
        audit # => "#{self}::#{method}:#{line}"
      end

    end