Question

Which log level should be used, is it org.slf4j.logger.Logger.trace or debug for logging the low level developer logs?

Answer 1

This is a good list describing the log levels:

• Debug
  This is the most verbose logging level (maximum volume setting). I usually consider Debug to be out-of-bounds for a production system and used it only for development and testing. I prefer to aim to get my logging levels just right so I have just enough information and endeavour to log this at the Information level or above.

• Information
  The Information level is typically used to output information that is useful to the running and management of your system. Information would also be the level used to log Entry and Exit points in key areas of your application. However, you may choose to add more entry and exit points at Debug level for more granularity during development and testing.

• Warning
  Warning is often used for handled ‘exceptions’ or other important log events. For example, if your application requires a configuration setting but has a default in case the setting is missing, then the Warning level should be used to log the missing configuration setting.

• Error
  Error is used to log all unhandled exceptions. This is typically logged inside a catch block at the boundary of your application.

• Fatal
  Fatal is reserved for special exceptions/conditions where it is imperative that you can quickly pick out these events. I normally wouldn’t expect Fatal to be used early in an application’s development. It’s usually only with experience I can identify situations worthy of the FATAL moniker experience do specific events become worth of promotion to Fatal. After all, an error’s an error.

From http://thejoyofcode.com/Logging_Levels_and_how_to_use_them.aspx