How to configure Log4r with Rails 3.0.x?

Hehe …The idea of Log4r comes from the famous “Log4j”, which is my favorite logger in my java programming life.
However log4r’s doc is really poor, and it’s really hard for newbies. Let me show my solution:

Step1. create the log4r config file: (file name: config/log4r.yml)

log4r_config:
  # define all loggers ...
  loggers:
    - name      : production
      level     : WARN
      trace     : 'false'
      outputters :
      - datefile
    - name      : development
      level     : DEBUG
      trace     : 'true'
      outputters :
      - datefile

  # define all outputters (incl. formatters)
  outputters:
  - type: DateFileOutputter
    name: datefile
    dirname: "log"
    # notice the file extension is needed! 
    # if you want the file is named by the process, just comment it,
    # then it will automatically get the same name with its process,
    # e.g.  rails_2017-05-03.log
    filename: "my_app.log" 
    formatter:
      date_pattern: '%H:%M:%S'
      pattern     : '%d %l: %m '
      type        : PatternFormatter

step2. modify config/application.rb

require 'rails/all'
# add these line for log4r
require 'log4r'
require 'log4r/yamlconfigurator'
require 'log4r/outputter/datefileoutputter'
include Log4r

Bundler.require(:default, Rails.env) if defined?(Bundler)
module Zurich
  class Application < Rails::Application
    #...
    # assign log4r's logger as rails' logger.
    log4r_config= YAML.load_file(File.join(File.dirname(__FILE__),"log4r.yml"))
    YamlConfigurator.decode_yaml( log4r_config['log4r_config'] )
    config.logger = Log4r::Logger[Rails.env]
  end
end

step3. add this line to your Gemfile.

# which is the latest version and support "datefileoutputter"
gem 'log4r', '1.1.9'  

(if you are using Rails 4+ (including Rails6), there still is step4: add this file to config/initializers folder

# config/initializers/log4r_patch_for_rails4.rb
class Log4r::Logger
  def formatter()       # for rails4+
    Proc.new{|severity, time, progname, msg|
      formatted_severity = sprintf("%-5s",severity.to_s)
      formatted_time = time.strftime("%Y-%m-%d %H:%M:%S")
      "[#{formatted_severity} #{formatted_time} #{$$}]\n #{msg}\n"
    }

  end
  def formatter= temp   # for rails6+
  end
end  

)

It’s done. Now “cd” into your Rails application folder, run “bundle” to install log4r, then “rails s”,
you will find the log files in “/log” folder like this:

May  9 17:05 rails_2011-05-09.log
May 10 13:42 rails_2011-05-10.log

and the log content is( my favorite format ) :

$ tail log/rails_2011-05-10.log
Started GET "/????_settings/19/edit" for 127.0.0.1 at ...
13:42:11 INFO:   Processing by ????SettingsController ...
13:42:11 INFO:   Parameters: {"id"=>"19"}
13:42:12 DEBUG:   ????Setting Load (0.0ms)  SELECT "d ...
13:42:12 INFO: Completed 200 OK in 750ms

My environment:

1. OS: cygwin running in XP
2. ruby 1.8.7 (2011-02-18 patchlevel 334) [i386-mingw32]
3. rails: 3.0.5
4. gem: 1.6.0

Any question please let me know~ 🙂

refer to: https://stackoverflow.com/a/20154414/445908
,and rails6 log4r tagged_logging.rb:22:in `call’: wrong number of arguments