# axum-tracing-opentelemetry

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[![crate version](https://img.shields.io/crates/v/axum-tracing-opentelemetry.svg)](https://crates.io/crates/axum-tracing-opentelemetry)

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Middlewares to integrate axum + tracing + opentelemetry.

- Read OpenTelemetry header from incoming request
- Start a new trace if no trace found in the incoming request
- Trace is attached into tracing'span
- OpenTelemetry Span is created on close of the tracing's span (behavior from [tracing-opentelemetry])

For examples, you can look at the [examples](https://github.com/davidB/tracing-opentelemetry-instrumentation-sdk/tree/main/examples/) folder.

```txt
//...
use axum_tracing_opentelemetry::opentelemetry_tracing_layer;

#[tokio::main]
async fn main() -> Result<(), axum::BoxError> {
    // very opinionated init of tracing, look at the source to make your own
    let _guard = init_tracing_opentelemetry::tracing_subscriber_ext::init_subscribers()?;

    let app = app();
    // run it
    let addr = &"0.0.0.0:3000".parse::<SocketAddr>()?;
    tracing::warn!("listening on {}", addr);
    let listener = tokio::net::TcpListener::bind(addr).await?;
    axum::serve(listener, app.into_make_service()).await?;
    Ok(())
}

fn app() -> Router {
    Router::new()
        .route("/", get(index)) // request processed inside span
        // include trace context as header into the response
        .layer(OtelInResponseLayer::default())
        //start OpenTelemetry trace on incoming request
        .layer(OtelAxumLayer::default())
        .route("/health", get(health)) // request processed without span / trace
}
```

For more info about how to initialize, you can look at crate [`init-tracing-opentelemetry`] or [`tracing-opentelemetry`].

## Changelog - History

[CHANGELOG.md](https://github.com/davidB/tracing-opentelemetry-instrumentation-sdk/blob/main/CHANGELOG.md)

[`tracing-opentelemetry`]: https://crates.io/crates/tracing-opentelemetry
[`init-tracing-opentelemetry`]: https://crates.io/crates/init-tracing-opentelemetry