1 files changed, 83 insertions, 0 deletions
diff --git a/src/metrics.rs b/src/metrics.rs
new file mode 100644
index 0000000..c635269
--- /dev/null
+++ b/src/metrics.rs
@@ -0,0 +1,83 @@
+use std::convert::Infallible;
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use anyhow::Result;
+use futures::future::*;
+use log::*;
+
+use hyper::{
+	header::CONTENT_TYPE,
+	service::{make_service_fn, service_fn},
+	Body, Method, Request, Response, Server,
+};
+use opentelemetry_prometheus::PrometheusExporter;
+use prometheus::{Encoder, TextEncoder};
+
+pub struct MetricsServer {
+	bind_addr: Option<SocketAddr>,
+	exporter: PrometheusExporter,
+}
+
+impl MetricsServer {
+	pub fn init(bind_addr: Option<SocketAddr>) -> MetricsServer {
+		let exporter = opentelemetry_prometheus::exporter().init();
+		Self {
+			bind_addr,
+			exporter,
+		}
+	}
+
+	pub async fn run(self, shutdown_signal: impl Future<Output = ()>) -> Result<()> {
+		if let Some(addr) = self.bind_addr {
+			let metrics_server = Arc::new(self);
+
+			let make_svc = make_service_fn(move |_conn| {
+				let metrics_server = metrics_server.clone();
+				async move {
+					Ok::<_, Infallible>(service_fn(move |req| {
+						metrics_server.clone().serve_req(req)
+					}))
+				}
+			});
+
+			let server = Server::bind(&addr).serve(make_svc);
+			let graceful = server.with_graceful_shutdown(shutdown_signal);
+			info!("Metrics server listening on http://{}", addr);
+
+			graceful.await?;
+		} else {
+			info!("Metrics server is disabled");
+		}
+
+		Ok(())
+	}
+
+	async fn serve_req(
+		self: Arc<MetricsServer>,
+		req: Request<Body>,
+	) -> Result<Response<Body>, hyper::Error> {
+		debug!("{} {}", req.method(), req.uri());
+
+		let response = match (req.method(), req.uri().path()) {
+			(&Method::GET, "/metrics") => {
+				let mut buffer = vec![];
+				let encoder = TextEncoder::new();
+				let metric_families = self.exporter.registry().gather();
+				encoder.encode(&metric_families, &mut buffer).unwrap();
+
+				Response::builder()
+					.status(200)
+					.header(CONTENT_TYPE, encoder.format_type())
+					.body(Body::from(buffer))
+					.unwrap()
+			}
+			_ => Response::builder()
+				.status(404)
+				.body(Body::from("Not implemented"))
+				.unwrap(),
+		};
+
+		Ok(response)
+	}
+}