How to enable logging/tracing with Axum? - rust

Question

Learning Axum and I will like to add logging to a service I have put together, but unfortunately I cannot get it to work.
What I have done?
I added tower-http = { version = "0.3.5", features = ["trace"] } to Cargo.html and in the definition of the service I have this:
use tower_http::trace::TraceLayer;
let app = Router::new()
.route("/:name/path", axum::routing::get(handler))
.layer(TraceLayer::new_for_http())
But when I start the application and make requests to the endpoint, nothing gets logged.
Is there any configuration step I could have missed?
** Edit 1 **
As suggested in the comment, I added the tracing-subscriber crate:
tracing-subscriber = { version = "0.3"}
and updated the code as follows:
use tower_http::trace::TraceLayer;
use tower_http::trace::TraceLayer;
tracing_subscriber::fmt().init();
let app = Router::new()
.route("/:name/path", axum::routing::get(handler))
.layer(TraceLayer::new_for_http())
But yet, still no log output.
** Edit 2 **
Ok so what finally worked was
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
and then initilize as follows:
tracing_subscriber::registry()
.with(tracing_subscriber::fmt::layer())
.init();
Even though this get the log output, I cannot explain why. So perhaps someone who understands how these crates work can give an explanation which I can accept as the answer to the question

Answer 1

You can get up and running quickly with the tracing-subscriber crate:
tracing_subscriber::fmt()
.with_max_level(tracing::Level::DEBUG)
.init();
The difference in the above attempts is simply a case of defaults. By default, TraceLayer will log with a DEBUG level. Using fmt() is configured with a default INFO logging level while registry().with(..).init() does not configure a log level filter.
You can also change the behavior of TraceLayer by using the customizable on_* methods.
See also:
How to use the tracing library? for more introductory tracing configurations
How to log and filter requests with Axum/Tokio? to help reduce the noise