How to configure Log4r with Rails 3.0.x?

Question

I tried configuring log4r with Rails 3.0.4 based on this article: http://www.dansketcher.com/2007/06/16/integrating-log4r-and-ruby-on-rails/

/Users/toto/.rvm/gems/ruby-1.9.2-p0/gems/log4r-1.1.9/lib/log4r/yamlconfigurator.rb:166:in `sub!': can't convert Pathname into String (TypeError)
    from /Users/toto/.rvm/gems/ruby-1.9.2-p0/gems/log4r-1.1.9/lib/log4r/yamlconfigurator.rb:166:in `block in paramsub'
    from /Users/toto/.rvm/gems/ruby-1.9.2-p0/gems/log4r-1.1.9/lib/log4r/yamlconfigurator.rb:165:in `each'
    from /Users/toto/.rvm/gems/ruby-1.9.2-p0/gems/log4r-1.1.9/lib/log4r/yamlconfigurator.rb:165:in `paramsub'
    from /Users/toto/.rvm/gems/ruby-1.9.2-p0/gems/log4r-1.1.9/lib/log4r/yamlconfigurator.rb:156:in `block in decode_hash_params'

I have Googled for a Rails 3 integration, but have not found a working solution. Can anyone point me to a working code snippet that will allow log configuration using a YAML file, and initialization at runtime?

Just as a reference, I placed the sample logger.rb in the config/initializers folder and the log4r.yml in the config directory.

Thanks

Answer 1

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

Answer 2

To mimic rails logging behavior (logging into environment dependend logfiles) I use the following log4r.yml:

log4r_config:
  # define all loggers ...
  loggers:
  - name      : production
    level     : WARN
    trace     : 'false'
    outputters :
    - datefile_production
  - name      : development
    level     : DEBUG
    trace     : 'true'
    outputters :
    - datefile_development
  - name      : test
    level     : DEBUG
    trace     : 'true'
    outputters :
    - datefile_test

  # define all outputters (incl. formatters)
  outputters:
  - type: DateFileOutputter
    name: datefile_production
    dirname: "log"
    filename: "production.log"
    formatter:
      date_pattern: '%H:%M:%S'
      pattern     : '%d %l: %m '
      type        : PatternFormatter
  - type: DateFileOutputter
    name: datefile_development
    dirname: "log"
    filename: "development.log"
    formatter:
      date_pattern: '%H:%M:%S'
      pattern     : '%d %l: %m '
      type        : PatternFormatter
  - type: DateFileOutputter
    name: datefile_test
    dirname: "log"
    filename: "test.log"
    formatter:
      date_pattern: '%H:%M:%S'
      pattern     : '%d %l: %m '
      type        : PatternFormatter

Answer 3

Can anyone point me to a working code snippet that will allow log configuration using a YAML file, and initialization at runtime?

I wrote a detailed blogpost about how to set up log4r in a way that it replaces the standard rails logger. Furthermore I went into detail about how to use multiple loggers, use log levels as well as how to log Mongoid, ActiveRecord and Exceptions(incluing Stack traces) using Log4r.

Another apparently more mature gem called "Logging" was suggested in comments on the HackerNews thread corresponding to the article, so people interested in Log4r might want to check on this gem as well.