Is it possible to use the tracing crate within handlers?

[harrytucker]

First off thanks for all the work that everyone put into 0.5, I'm playing around with it and it looks fantastic 😄

In 0.5 I understand that Rocket's logging infrastructure has been migrated to the tracing crate. After skimming through the API docs for logging items I can't find any examples of logging. This minimal example results in no logging output from the info! call within the handler:

#[macro_use] extern crate rocket;
#[macro_use] extern crate tracing;

#[get("/<name>/<age>")]
fn hello(name: &str, age: u8) -> String {
    info!(
        ?name,
        ?age,
        "Processing request",
    );
    format!("Hello, {} year old named {}!", age, name)
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount("/hello", routes![hello])
}

I have an application built on actix that I'd like to port over to the new release which uses tracing throughout, am I missing something obvious in the docs? Or is it not currently possible to hook into Rocket's logging facilities?

[SergioBenitez]

In 0.5 I understand that Rocket's logging infrastructure has been migrated to the tracing crate.

This unfortunately isn't the case yet. #21 and #1579 are the latest on moving over to tracing. For now, Rocket still uses log. We don't document how to tap in in hopes of being able to migrate to tracing in a non-breaking release. But in a pinch, using log macros will work and should continue to work even when we do migrate to tracing.

[harrytucker]

Ah cool, thanks for the heads-up! 👍

[SergioBenitez]

See also this part of @jebrosen's response:

In the meantime, tracing can emit log events in addition to tracing events; these events would be seen by Rocket's default logger. Another possible option is to register your own tracing subscriber that captures log events (including those emitted by rocket) before rocket's logger can be initialized. Neither of these options are thoroughly supported and there are a few wrinkles; nonetheless, they might be a suitable choice in some situations.