chore(examples): add axum example

Cargo.toml

@@ -27,6 +27,7 @@ prost-types = { version = "0.12.0", optional = true }
 
 [dev-dependencies]
 async-std = { version = "1", features = ["attributes"] }
+axum = "0.7"
 criterion = "0.5"
 http-types = "2"
 pyo3 = "0.21"

examples/axum.rs

@@ -0,0 +1,88 @@
+use axum::body::Body;
+use axum::extract::State;
+use axum::http::header::CONTENT_TYPE;
+use axum::http::StatusCode;
+use axum::response::{IntoResponse, Response};
+use axum::routing::get;
+use axum::Router;
+use prometheus_client::encoding::text::encode;
+use prometheus_client::metrics::counter::Counter;
+use prometheus_client::metrics::family::Family;
+use prometheus_client::registry::Registry;
+use prometheus_client_derive_encode::{EncodeLabelSet, EncodeLabelValue};
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq, EncodeLabelValue)]
+pub enum Method {
+    Get,
+    Post,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq, EncodeLabelSet)]
+pub struct MethodLabels {
+    pub method: Method,
+}
+
+#[derive(Debug)]
+pub struct Metrics {
+    requests: Family<MethodLabels, Counter>,
+}
+
+impl Metrics {
+    pub fn inc_requests(&self, method: Method) {
+        self.requests.get_or_create(&MethodLabels { method }).inc();
+    }
+}
+
+#[derive(Debug)]
+pub struct AppState {
+    pub registry: Registry,
+}
+
+pub async fn metrics_handler(State(state): State<Arc<Mutex<AppState>>>) -> impl IntoResponse {
+    let state = state.lock().await;
+    let mut buffer = String::new();
+    encode(&mut buffer, &state.registry).unwrap();
+
+    Response::builder()
+        .status(StatusCode::OK)
+        .header(
+            CONTENT_TYPE,
+            "application/openmetrics-text; version=1.0.0; charset=utf-8",
+        )
+        .body(Body::from(buffer))
+        .unwrap()
+}
+
+pub async fn some_handler(State(metrics): State<Arc<Mutex<Metrics>>>) -> impl IntoResponse {
+    metrics.lock().await.inc_requests(Method::Get);
+    "okay".to_string()
+}
+
+#[tokio::main]
+async fn main() {
+    let metrics = Metrics {
+        requests: Family::default(),
+    };
+    let mut state = AppState {
+        registry: Registry::default(),
+    };
+    state
+        .registry
+        .register("requests", "Count of requests", metrics.requests.clone());
+    let metrics = Arc::new(Mutex::new(metrics));
+    let state = Arc::new(Mutex::new(state));
+
+    let router = Router::new()
+        .route("/metrics", get(metrics_handler))
+        .with_state(state)
+        .route("/handler", get(some_handler))
+        .with_state(metrics);
+    let port = 8080;
+    let listener = tokio::net::TcpListener::bind(format!("0.0.0.0:{}", port))
+        .await
+        .unwrap();
+
+    axum::serve(listener, router).await.unwrap();
+}