1 files changed, 211 insertions, 0 deletions
diff --git a/src/api/generic_server.rs b/src/api/generic_server.rs
new file mode 100644
index 00000000..62fe4e5a
--- /dev/null
+++ b/src/api/generic_server.rs
@@ -0,0 +1,211 @@
+use std::net::SocketAddr;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+
+use futures::future::Future;
+
+use hyper::header::HeaderValue;
+use hyper::server::conn::AddrStream;
+use hyper::service::{make_service_fn, service_fn};
+use hyper::{Body, Request, Response, Server};
+use hyper::{HeaderMap, StatusCode};
+
+use opentelemetry::{
+	global,
+	metrics::{Counter, ValueRecorder},
+	trace::{FutureExt, SpanRef, TraceContextExt, Tracer},
+	Context, KeyValue,
+};
+
+use garage_util::error::Error as GarageError;
+use garage_util::metrics::{gen_trace_id, RecordDuration};
+
+pub(crate) trait ApiEndpoint: Send + Sync + 'static {
+	fn name(&self) -> &'static str;
+	fn add_span_attributes(&self, span: SpanRef<'_>);
+}
+
+pub trait ApiError: std::error::Error + Send + Sync + 'static {
+	fn http_status_code(&self) -> StatusCode;
+	fn add_http_headers(&self, header_map: &mut HeaderMap<HeaderValue>);
+	fn http_body(&self, garage_region: &str, path: &str) -> Body;
+}
+
+#[async_trait]
+pub(crate) trait ApiHandler: Send + Sync + 'static {
+	const API_NAME: &'static str;
+	const API_NAME_DISPLAY: &'static str;
+
+	type Endpoint: ApiEndpoint;
+	type Error: ApiError;
+
+	fn parse_endpoint(&self, r: &Request<Body>) -> Result<Self::Endpoint, Self::Error>;
+	async fn handle(
+		&self,
+		req: Request<Body>,
+		endpoint: Self::Endpoint,
+	) -> Result<Response<Body>, Self::Error>;
+}
+
+pub(crate) struct ApiServer<A: ApiHandler> {
+	region: String,
+	api_handler: A,
+
+	// Metrics
+	request_counter: Counter<u64>,
+	error_counter: Counter<u64>,
+	request_duration: ValueRecorder<f64>,
+}
+
+impl<A: ApiHandler> ApiServer<A> {
+	pub fn new(region: String, api_handler: A) -> Arc<Self> {
+		let meter = global::meter("garage/api");
+		Arc::new(Self {
+			region,
+			api_handler,
+			request_counter: meter
+				.u64_counter(format!("api.{}.request_counter", A::API_NAME))
+				.with_description(format!(
+					"Number of API calls to the various {} API endpoints",
+					A::API_NAME_DISPLAY
+				))
+				.init(),
+			error_counter: meter
+				.u64_counter(format!("api.{}.error_counter", A::API_NAME))
+				.with_description(format!(
+					"Number of API calls to the various {} API endpoints that resulted in errors",
+					A::API_NAME_DISPLAY
+				))
+				.init(),
+			request_duration: meter
+				.f64_value_recorder(format!("api.{}.request_duration", A::API_NAME))
+				.with_description(format!(
+					"Duration of API calls to the various {} API endpoints",
+					A::API_NAME_DISPLAY
+				))
+				.init(),
+		})
+	}
+
+	pub async fn run_server(
+		self: Arc<Self>,
+		bind_addr: SocketAddr,
+		shutdown_signal: impl Future<Output = ()>,
+	) -> Result<(), GarageError> {
+		let service = make_service_fn(|conn: &AddrStream| {
+			let this = self.clone();
+
+			let client_addr = conn.remote_addr();
+			async move {
+				Ok::<_, GarageError>(service_fn(move |req: Request<Body>| {
+					let this = this.clone();
+
+					this.handler(req, client_addr)
+				}))
+			}
+		});
+
+		let server = Server::bind(&bind_addr).serve(service);
+
+		let graceful = server.with_graceful_shutdown(shutdown_signal);
+		info!(
+			"{} API server listening on http://{}",
+			A::API_NAME_DISPLAY,
+			bind_addr
+		);
+
+		graceful.await?;
+		Ok(())
+	}
+
+	async fn handler(
+		self: Arc<Self>,
+		req: Request<Body>,
+		addr: SocketAddr,
+	) -> Result<Response<Body>, GarageError> {
+		let uri = req.uri().clone();
+		info!("{} {} {}", addr, req.method(), uri);
+		debug!("{:?}", req);
+
+		let tracer = opentelemetry::global::tracer("garage");
+		let span = tracer
+			.span_builder(format!("{} API call (unknown)", A::API_NAME_DISPLAY))
+			.with_trace_id(gen_trace_id())
+			.with_attributes(vec![
+				KeyValue::new("method", format!("{}", req.method())),
+				KeyValue::new("uri", req.uri().to_string()),
+			])
+			.start(&tracer);
+
+		let res = self
+			.handler_stage2(req)
+			.with_context(Context::current_with_span(span))
+			.await;
+
+		match res {
+			Ok(x) => {
+				debug!("{} {:?}", x.status(), x.headers());
+				Ok(x)
+			}
+			Err(e) => {
+				let body: Body = e.http_body(&self.region, uri.path());
+				let mut http_error_builder = Response::builder().status(e.http_status_code());
+
+				if let Some(header_map) = http_error_builder.headers_mut() {
+					e.add_http_headers(header_map)
+				}
+
+				let http_error = http_error_builder.body(body)?;
+
+				if e.http_status_code().is_server_error() {
+					warn!("Response: error {}, {}", e.http_status_code(), e);
+				} else {
+					info!("Response: error {}, {}", e.http_status_code(), e);
+				}
+				Ok(http_error)
+			}
+		}
+	}
+
+	async fn handler_stage2(&self, req: Request<Body>) -> Result<Response<Body>, A::Error> {
+		let endpoint = self.api_handler.parse_endpoint(&req)?;
+		debug!("Endpoint: {}", endpoint.name());
+
+		let current_context = Context::current();
+		let current_span = current_context.span();
+		current_span.update_name::<String>(format!(
+			"{} API {}",
+			A::API_NAME_DISPLAY,
+			endpoint.name()
+		));
+		current_span.set_attribute(KeyValue::new("endpoint", endpoint.name()));
+		endpoint.add_span_attributes(current_span);
+
+		let metrics_tags = &[KeyValue::new("api_endpoint", endpoint.name())];
+
+		let res = self
+			.api_handler
+			.handle(req, endpoint)
+			.record_duration(&self.request_duration, &metrics_tags[..])
+			.await;
+
+		self.request_counter.add(1, &metrics_tags[..]);
+
+		let status_code = match &res {
+			Ok(r) => r.status(),
+			Err(e) => e.http_status_code(),
+		};
+		if status_code.is_client_error() || status_code.is_server_error() {
+			self.error_counter.add(
+				1,
+				&[
+					metrics_tags[0].clone(),
+					KeyValue::new("status_code", status_code.as_str().to_string()),
+				],
+			);
+		}
+
+		res
+	}
+}