Add request id example (#2912)

examples/request-id/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "example-request-id"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+axum = { path = "../../axum" }
+tokio = { version = "1.0", features = ["full"] }
+tower = "0.5"
+tower-http = { version = "0.5", features = ["request-id", "trace"] }
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }

examples/request-id/src/main.rs

@@ -0,0 +1,81 @@
+//! Run with
+//!
+//! ```not_rust
+//! cargo run -p example-request-id
+//! ```
+
+use axum::{
+    http::{HeaderName, Request},
+    response::Html,
+    routing::get,
+    Router,
+};
+use tower::ServiceBuilder;
+use tower_http::{
+    request_id::{MakeRequestUuid, PropagateRequestIdLayer, SetRequestIdLayer},
+    trace::TraceLayer,
+};
+use tracing::{error, info, info_span};
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
+
+const REQUEST_ID_HEADER: &str = "x-request-id";
+
+#[tokio::main]
+async fn main() {
+    tracing_subscriber::registry()
+        .with(
+            tracing_subscriber::EnvFilter::try_from_default_env().unwrap_or_else(|_| {
+                // axum logs rejections from built-in extractors with the `axum::rejection`
+                // target, at `TRACE` level. `axum::rejection=trace` enables showing those events
+                format!(
+                    "{}=debug,tower_http=debug,axum::rejection=trace",
+                    env!("CARGO_CRATE_NAME")
+                )
+                .into()
+            }),
+        )
+        .with(tracing_subscriber::fmt::layer())
+        .init();
+
+    let x_request_id = HeaderName::from_static(REQUEST_ID_HEADER);
+
+    let middleware = ServiceBuilder::new()
+        .layer(SetRequestIdLayer::new(
+            x_request_id.clone(),
+            MakeRequestUuid,
+        ))
+        .layer(
+            TraceLayer::new_for_http().make_span_with(|request: &Request<_>| {
+                // Log the request id as generated.
+                let request_id = request.headers().get(REQUEST_ID_HEADER);
+
+                match request_id {
+                    Some(request_id) => info_span!(
+                        "http_request",
+                        request_id = ?request_id,
+                    ),
+                    None => {
+                        error!("could not extract request_id");
+                        info_span!("http_request")
+                    }
+                }
+            }),
+        )
+        // send headers from request to response headers
+        .layer(PropagateRequestIdLayer::new(x_request_id));
+
+    // build our application with a route
+    let app = Router::new().route("/", get(handler)).layer(middleware);
+
+    // run it
+    let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
+        .await
+        .unwrap();
+    println!("listening on {}", listener.local_addr().unwrap());
+    axum::serve(listener, app).await.unwrap();
+}
+
+async fn handler() -> Html<&'static str> {
+    info!("Hello world!");
+    Html("<h1>Hello, World!</h1>")
+}