How to use tokio tracing for async debugging

Enable tracing by adding the tracing and tracing-subscriber crates to your Cargo.toml and initializing the subscriber in main before running async tasks.

[dependencies]
tokio = { version = "1", features = ["rt-multi-thread", "macros"] }
tracing = "0.1"
tracing-subscriber = "0.3"

use tracing_subscriber;

#[tokio::main]
async fn main() {
    tracing_subscriber::fmt::init();
    // Your async code here
}

Add #[tracing::instrument] to async functions to automatically log entry, exit, and arguments.

Tracing acts like a dashboard for your async code, showing exactly when tasks start, finish, and what data they are processing. It matters because async code runs in parallel, making it hard to see where delays or errors happen without a timeline. Think of it as a flight recorder for your program that logs every step so you can replay the sequence of events.