Practices for Logging in a desktop application

Question

Hi, We are developing a desktop application(visual basic 6.0).We have our own logging framework. What are good practices? When we have a web application, then we can control the level of logging. How to go about in a desktop app?

Answer 1

Any answer needs to be considered based on your environment:

• Do your business rules (or laws) require certain activities to be logged?
• Is security an issue?
• Do actions need to be traceable?
• Is the size of the log file (or the amount of disk space) an issue?
• Is your motivation to record activity, to debug, or both?

With those in mind:

• Consider allowing the user to select the verbosity, or "logging level."
• Log all program errors and significant user errors.
• Log any activities that affect system configuration or operation.
• Log the start and end of user sessions.
• Log the start and end of the application.
• Consider logging the first time a significant activity occurs.

Other suggestions:

• Include timestamps, either in each log or at the beginning of a "group" of logs, as best appropriate for your application.
• If you're logging to a file, consider rotating the log (i.e. closing one file and opening a new one) when it reaches a certain size or age.
• If the application contains several modules, include the name of the module in each log.
• If more than one person uses the application (shared computer?), log the user ID at the beginning of each session.
• Assign log "levels" based on the severity (Error, Warning, Info, Debug). The syslog specification defines 7 "standard" levels that serve as a good reference.
• Ask your customer what they expect to see in the log.

Answer 2

An important feature to consider is to allow for adjustment of the log level dynamically at run time without requiring stopping and restarting the application (I've implemented this on *nix with a custom signal handler). This is a great help when debugging in the field.

Many times, a misbehaving application will behave fine when restarted. Dynamically tweakable log levels let you see whats going on before you release all your resources back to the OS.