# axum-trace-id

[Axum] middleware for adding trace ids to requests.

# Basic Usage

Adding the `SetTraceIdLayer<T>` layer will make `TraceId<T>` available via the request and 
response extensions. The crate also provides an extractor to access the trace id in a handler. 
For special use-cases (e.g. lazily generating trace ids only in case of http errors) you can implement `MakeTraceId` on your type.

```rust
use axum::{routing::get, Router};
use axum_trace_id::{SetTraceIdLayer, TraceId};

let app: Router = Router::new()
     .route(
         "/",
         get(|trace_id: TraceId<String>| async move { trace_id.to_string() }),
     )
     .layer(SetTraceIdLayer::<String>::new());
```

# Use with [tracing]
To use with [tracing], you can access the requests tracing id via the extensions.

```rust
use axum::{http::Request, routing::get, Router};
use axum_trace_id::{SetTraceIdLayer, TraceId};
use tower_http::trace::TraceLayer;
use tracing::info_span;

let app = Router::new()
    .route("/", get(|| async { "" }))
    .layer(TraceLayer::new_for_http().make_span_with(|request: &Request<_>| {
        let trace_id = request.extensions().get::<TraceId<String>>().unwrap();

        info_span!("http_request", trace_id = trace_id)
    }));
```

# License

This project is licensed under the [MIT license](LICENSE).

[axum]: https://crates.io/crates/axum
[tracing]: https://crates.io/crates/tracing