Purpose of levels

[Kinrany]

As far as I can tell, there is no consensus on the meaning of individual verbosity levels.

What is the purpose of tracing::Level? Is there a benefit over asking users to define their own levels?

[kriswuollett]

It seems like Level is useful from the Rust perspective in that that it is a coarse way of defining whether or not the parameters would be evaluated and/or passed on based on scoping settings similar to what is in env_logger. The benefit may be that developers can add DEBUG or TRACE events or spans during testing that won't get included when running in prod.

I don't think there is a universally accepted way to define levels, so I'm just expecting that I'll need add one or more fields like the one I'd set up if I use tracing-stackdriver for GCP's levels.

[davidbarsky]

What @kriswuollett said is generally correct. Most applications only care about INFO and ERROR—which are generally the defaults folks should use—but few applications stay as just applications. There are a few other reasons as why we provide levels (compatibility with the log crate, having a standard type people can refer to...), but those are the big ones.