### 新建一个log4r的配置文件： 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"
    filename: "my_app.log" # notice the file extension is needed!
    formatter:
      date_pattern: '%H:%M:%S'
      pattern     : '%d %l: %m '
      type        : PatternFormatter