What logging is good logging for your app?

Question

So we\'ve discussed logging in passing at my place of work and I was wondering if some of you guys here could give me some ideas of your approaches?

Typically our scenar

Answer 1

Is it better to go all the way and log everything across multiple attempts/days, or log only what you need to (given hdd is cheap).

The fact harddrives are cheap really isn't a good reason to verbosely log everything possible, for a few reasons.. For one, with a very busy application, you really don't want to slow it down and tie up disc-writes writing logs (harddrives are pretty slow). The second point, and the more important one - there's really very little to gain from terabytes worth of logs.. For development, they can are useful, but you don't need to keep more than a few minutes of them..

Some logging is of course useful, having different levels is about the only way to go about it - for example debug() info() only get logged if requested (in a config, or command line flag), then maybe warning() and error() get sent to a log file

For most of the things I've written (smallish scripts) I generally just have a debug() function, that checks if --verbose is set, and prints the message.. That way I can shove debug("some value: %s" % (avar)) when needed, and not have to worry about going back and removing debugging print() statements everwhere.

For web applications, I generally just use the web-server logs for statistics, and the error log. I use things like mod_rewrite's log when needed, but it would be idiotic to leave this enabled beyond development (as it creates many many lines on each page request)

I suppose it depends on the application itself, but generally, for big applications use multiple levels of logs that can be activated when needed. For smaller things, a --verbose flag or equivalent, for web applications, log errors and (to a point) log hits.

Basically, in "production" log only the information you can use, in development log everything you could possible need to fix problems.