Update README.md

README.md

@@ -1,6 +1,6 @@
 # axum-app-wrapper
 
-A small plugin layer for `axum` applications, inspired by [fastify](https://fastify.dev/) from the Node/JS ecossytem.
+A small plugin layer for `axum` applications, inspired by [fastify](https://fastify.dev/) from the Node/JS ecosystem.
 
 Plugins can:
 
@@ -27,12 +27,14 @@ use std::{net::SocketAddr, sync::Arc};
 use axum::{
     extract::State,
     routing::get,
+    Extension,
 };
 use axum_app_wrapper::{AdHocPlugin, App, AppState};
 
 #[derive(Clone, AppState)]
 struct AppState {
     config: Arc<Config>,
+    metrics: Arc<Metrics>,
 }
 
 #[derive(Clone)]
@@ -40,30 +42,64 @@ struct Config {
     service_name: String,
 }
 
+struct Metrics;
+
+impl Metrics {
+    fn new() -> Self {
+        Self
+    }
+
+    async fn flush(&self) {
+        tracing::info!("flushed metrics");
+    }
+}
+
 async fn health(State(state): State<AppState>) -> String {
     format!("{}:ok", state.config.service_name)
 }
 
+async fn metrics_handler(Extension(metrics): Extension<Arc<Metrics>>) -> &'static str {
+    let _metrics = metrics;
+    "metrics:ok"
+}
+
 #[tokio::main]
 async fn main() -> anyhow::Result<()> {
     let config = Arc::new(Config {
         service_name: "api".to_owned(),
     });
+    let metrics_registry = Arc::new(Metrics::new());
 
-    let app = App::<AppState>::new().register(
-        AdHocPlugin::<AppState>::new()
-            .on_init(async move |mut state| {
-                state.insert(config);
-                Ok(state)
-            })
-            .on_setup(|router, _state| Ok(router.route("/health", get(health))))
-            .on_shutdown(|state| {
-                let service_name = state.config.service_name.clone();
-                async move {
-                    tracing::info!(%service_name, "shutting down");
-                }
-            }),
-    );
+    let config_plugin = AdHocPlugin::<AppState>::new()
+        .on_init(async move |mut state| {
+            state.insert(config);
+            Ok(state)
+        })
+        .on_setup(|router, state| {
+            tracing::info!(service = %state.config.service_name, "configuring routes");
+            Ok(router.route("/health", get(health)))
+        });
+
+    let metrics_plugin = AdHocPlugin::<AppState>::new()
+        .on_init(async move |mut state| {
+            state.insert(metrics_registry);
+            Ok(state)
+        })
+        .on_setup(|router, state| {
+            Ok(router
+                .route("/metrics", get(metrics_handler))
+                .layer(Extension(Arc::clone(&state.metrics))))
+        })
+        .on_shutdown(|state| {
+            let metrics = Arc::clone(&state.metrics);
+            async move {
+                metrics.flush().await;
+            }
+        });
+
+    let app = App::<AppState>::new()
+        .register(config_plugin)
+        .register(metrics_plugin);
 
     let (router, state, on_shutdown) = app.init().await?;
     let router = router.with_state(state);