log4r yaml configurator, see http://stackoverflow.com/questions/2856205/log4r-logger-inheritance-yaml-configuration-alternatives

log4r yaml configurator example.rb

require 'log4r'
require 'log4r/yamlconfigurator'

include Log4r

y = "log4r_config:

  # define all loggers ...
  loggers:
    - name      : production
      level     : INFO
      trace     : 'false'
      outputters:
        - stdout

  # define all outputters (incl. formatters)      
  outputters:
    - type     : StdoutOutputter
      name     : stdout
      formatter:
        date_pattern: '%Y-%m-%d %H:%M:%S'
        pattern     : '%d %l: #\{TEST\} %m '
        type        : PatternFormatter"

h = YAML.load y
log_cfg = YamlConfigurator
log_cfg['TEST'] = 'foobar'
log_cfg.decode_yaml h['log4r_config']
@log = Logger['production']
@log.info 'test'
#=>2010-05-20 14:36:32 INFO: foobar test