For what it's worth, we're using the following log levels:
- DEBUG level messages give highly-detailed and/or specific information, only useful for tracking down problems.
- INFORMATION messages give general information about what the system is doing. (e.g. processing file X)
- WARNING messages warn the user about things which are not ideal, but should not affect the system. (e.g. configuration X missed out, using default value)
- ERROR messages inform the user that something has gone wrong, but the system should be able to cope. (e.g. connection lost, but will try again)
- CRITICAL messages inform the user when an un-recoverable error occurs. (i.e. I am about to abort the current task or crash)
I think the most important thing with log levels is to figure out a scheme, document it, and stick with it. Although making log level consistent between programs would be nice, as long as you've used common sense in defining your log levels, users will tolerate a certain amount of variance between programs.
