How to transform a String into a Level to be used with tracing_subscriber?

Question

I want to set the tracing Level using a String (because I get the Level from an env var).

let env_log_level = std::env::var("LOG_LEVEL").unwrap();

tracing_subscriber::fmt()
    .with_max_level(tracing::Level::DEBUG) // somehow use env_log_level here
    .with_target(false)
    .init();

I guess it should be a way to parse a String into a Level object but I don't see how.

Don't be discouraged by the downvotes, it is most likely because people think it's a too basic question for stackoverflow and would fall under [too little research effort before asking](https://meta.stackoverflow.com/questions/261592/how-much-research-effort-is-expected-of-stack-overflow-users). — Finomnis, Apr 30 '23 at 15:29

kmdreko · Accepted Answer · 2023-04-30T15:29:12.830

Level implements FromStr which accepts "error", "warn", "info", "debug", or "trace" (case-insensitive). So you can use that like so:

use std::str::FromStr;

let env_log_level = std::env::var("LOG_LEVEL").unwrap();

tracing_subscriber::fmt()
    .with_max_level(Level::from_str(&env_log_level).unwrap())
    .with_target(false)
    .init();

^{Note: I used ::from_str() instead of .parse() since .with_max_level() is generic and would need type annotations.}

As suggested by @Finomnis, a more feature-rich solution would be to take advantage of EnvFilter since it allows configuring a global log level and much more (see docs).

tracing_subscriber::fmt()
    .with_env_filter(EnvFilter::from_env("LOG_LEVEL"))
    .with_target(false)
    .init();

How to transform a String into a Level to be used with tracing_subscriber?

1 Answers1