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Logging Settings

Levels​

  • trace, debug, info, warn, error, fatal

Formats​

  • json, text, console

Outputs​

  • console, file
  • remote: not implemented; configuring it makes logger construction fail with NotImplemented

Production sampling​

Configure sampling to limit log volume in production.

Configuration keys​

logging:
  level: info      # default level; also the level of outputs that set none
  format: json     # console selects the colored development encoder
  outputs:         # optional; without it, logs go to the console
    - type: console
      enabled: true
    - type: file
      enabled: true
      level: warn
      path: logs/app.log   # rotated at 100 MB, 30 days, 10 backups

config.LoadSettings reads these into settings.Logging, and log.NewLoggerFromSettings(settings.Logging) builds the logger. An invalid level, format or output type is an error when the logger is built. Without a logging section the level is info and the format json.

An outputs value that is not a list of outputs, such as outputs: file or an entry whose enabled is not a boolean, cannot be read. LoadSettings then leaves settings.Logging.Outputs empty, so logs go to the console, and the server logs a warning naming logging.outputs when it starts. config.Config.SettingsWarnings returns these warnings for code that does not start a server.Server.

Generated projects​

The main.go written by forge new builds its logger with log.NewLoggerFromSettings(settings.Logging), and its config/config.yaml starts with level: debug and format: console for local development. Use format: json in production.