How to log something in Rails in an independent log file?

Question

In rails I want to log some information in a different log file and not the standard development.log or production.log. I want to do this logging from a model class.

Answer 1

You can create a Logger object yourself from inside any model. Just pass the file name to the constructor and use the object like the usual Rails logger:

class User < ActiveRecord::Base
  def my_logger
    @@my_logger ||= Logger.new("#{RAILS_ROOT}/log/my.log")
  end

  def before_save
    my_logger.info("Creating user with name #{self.name}")
  end
end

Here I used a class attribute to memoize the logger. This way it won't be created for every single User object that gets created, but you aren't required to do that. Remember also that you can inject the my_logger method directly into the ActiveRecord::Base class (or into some superclass of your own if you don't like to monkey patch too much) to share the code between you app's models.

Answer 2

class Article < ActiveRecord::Base  

      LOGFILE = File.join(RAILS_ROOT, '/log/', "article_#{RAILS_ENV}.log")  

      def validate  
        log "was validated!"  
      end   

      def log(*args)  
       args.size == 1 ? (message = args; severity = :info) : (severity, message = args)  
       Article.logger severity, "Article##{self.id}: #{message}"  
     end  

     def self.logger(severity = nil, message = nil)  
       @article_logger ||= Article.open_log  
       if !severity.nil? && !message.nil? && @article_logger.respond_to?(severity)  
         @article_logger.send severity, "[#{Time.now.to_s(:db)}] [#{severity.to_s.capitalize}] #{message}\n"  
       end  
       message or @article_logger  
     end  

     def self.open_log  
       ActiveSupport::BufferedLogger.new(LOGFILE)  
     end  

   end